What Practical Advice Can Readers Offer Regarding Home Solar PV? (Open thread)

I am sure there are at least a few readers who have solar PV installed, and others who are considering installing solar PV. Someone sent me an e-mail, asking if we could do a Campfire discussion of practical advice regarding solar PV, based on the experiences of readers who have tried it.

Below the fold are a few questions that come to mind. I am sure that if you are using solar PV, you may have answers to questions I haven't even thought of.

1. Is it best to work with someone who both sells and installs solar PV panels? Or is this something that people end up doing themselves, using a variety of vendors?

2. What brands/ types are best?

3. How much maintenance is required?

4. What experiences have people had who purchased solar PV, then moved to another home? Did the addition of solar PV help the resale value?

5. What have buyers experience with battery back-up been? Is a small amount worthwhile, even if a homeowner is on the grid?

6. Are there any particular issues with inverters that readers should be aware of?

7. If you have purchased solar PV, are you generally happy with it?

8. Where does one find good material to read regarding solar PV?

Hi Gail,

I used to design and sell solar PV for residential and small commercial buildings. I also have around 100 hours in the field helping to install them. Some quick answers to your questions:

1. I think it's best to work with a single contractor. In my solar work, I sold the equipment directly to the customer and then arranged for an installation contractor. I don't think the extra effort was worth it, though it may have been slightly cheaper for some customers.

2. The best brands are the ones that have been around the longest, and that qualify for incentives in your area. Here in California, only those modules and inverters on the approved list are eligible for rebates. Then look at verified, independent efficiency ratings, not the "nameplate" output numbers which can vary by 10% or more from their actual output.

3. Maintenance is very minimal under most circumstances:
- Wash off the modules with soap and water as needed (usually once or twice a year). Like a window, they don't work as well when covered with dust, pollen, etc.
- Keep vegetation trimmed back so it doesn't shade the modules, or keep air circulating around the inverter.

4. It does appear that in my area, solar systems do help the resale value. They're also exempt from property tax here.

5. Battery back-up is nice to have, but expensive. I typically only recommended it for those customers who really wanted it, or who were insensitive enough to the cost that they'd buy it just for the peace of mind...particularly in areas where the grid can be down for several days to a week in the storm season.

6. Not really. Customers should budget to replace their inverters every 10-15 years however, because they do wear out. Their longevity depends on how well they're made, and how they're loaded by the PV array. For better longevity, it's better to leave a little headroom than try to max out every string.

7. My former customers are all still very happy with their systems, as far as I am aware.

8. For information on local incentives, installers, and so on, see the Database of State Incentives for Renewable Energy (DSIRE)

Another terrific resource is Home Power Magazine. I've subscribed to it for years. It's always informative with plenty of technical information, and they have some bona fide experts who are very good at responding to reader questions.

I currently both sell and install commercial and residential PV systems in South Florida.

I agree with most of the points mentioned by ChrisN.

Since in South Florida we experience hurricanes most of our customers are interested in battery back up. I disagree that it is expensive, at least when the total cost of a system is considered.
Granted it is an added cost.

I also strongly recommend working with a single reputable contractor.

Home Power Magazine and DSIRE are also resources I can recommend wholeheartedly.

In my area I am finding a niche for completely off grid systems especially for boat docks and farms.

Based on my reading of the other comments so far I can agree that energy efficient appliances and energy conservation are a big part of the overall equation for anyone considering PV.

I'm also a big proponent for passive solar hot water and am convinced that at least in Florida it should be mandatory.

I agree with the Home Power and DSIRE recommendations.

Solar Pro magazine is also a very good resource if you are involved with installation and design. The Dec/Jan '10 issue has a big article on grid-direct inverters. Also articles related to code issues, so maybe not as interesting to the general enthusiast as Home Power. I think you can get the electronic versions (pdfs) for free if you register.
Website: http://solarprofessional.com/home/

Related to the SunEye and Pathfinder tools - here in PG&E territory, you can check them out to use for free from the Pacific Energy Center in SF if you are a PG&E customer.

FMagyar - do you do any business up in North Florida, in the Jacksonville area? Or could you recommend any outfits up there?

FMagyar - do you do any business up in North Florida, in the Jacksonville area? Or could you recommend any outfits up there?

I haven't personally been up there, I'm generally in the Miami to West Palm Beach area.
While I'm not very familiar with contractors up in your area, I have worked with a contractor called Veterans Energy Solutions Inc. They work all over the state and have done jobs as far away as Hawaii, if you'd like send me an email and I'll have them contact you. I might even go up there with them for a change of scenery.

We installed solar PV in 11/2004. Rather than repeat myself I'll just mention our website and you can read about our solar PV system there.


We live in NJ. House is passive solar heat. PV system and solar hot water. We are zero energy. In other words we make all energy we use onsite and in our case it's all solar energy.
Payback for the PV system was 3.5 years.

This seems better than the most speculative derivative fond - but with no risk involved what so ever ..

Payback for the PV system was 3.5 years

If this is true, why don't you invest in the largest solar-farm on the planet ? or ... maybe you are for what I know.
I mean, PVs stays alive for some 20 years and it's according to you "free and guaranteed" monies for at least 16,5 years after that. Quite a good deal if you ask me. Also, what's the fuss in the media regarding the fact that Germans , Spaniards are cutting back on their PV-subsidies ? For Good's sake these PV-systems need no subsidies if your claim is correct. What am I missing here ?

rbhollabaugh's site states that New Jersey's Clean Energy Program paid for about 70% of the system.

NJ (and PA and OH) allow you to sell "renewable energy credits" for your energy that you generate. The RECs are worth more than the power savings. NJ's are something like $680/1000 KwH while PAs are closer to $300. The price varies but it helps tremendously pay back (and more) for a solar system.

The RECs are worth more than the power savings. NJ's are something like $680/1000 KwH while PAs are closer to $300.

I thought someone had made a blunder when they claimed a three-and-a-half year payback time for a PV system. But, with paybacks like that, I can believe it.
Of course those sorts of RECs are patently absurd, so I gotta think they can't be sistained for long.

Quite a good deal if you ask me. Also, what's the fuss in the media regarding the fact that Germans , Spaniards are cutting back on their PV-subsidies ?

Besides that feed-in tariffs are no subsidies as they are not paid by the tax-payer. As far as the Germans are concerned they cut the feed-in tariffs by about 10% every single year because the PV-modules are gradually getting cheaper. This is very sensible. After all: We would not want PV companies to become as wealthy as non-producing banks.

I installed a 5.6kW pv system in the fall of 2008 in Nevada. I received quotes from a few installers in the area for around $55k. I ended up installing it myself for $14k less than that, including paying an electrician $2k to do the final connection to the main service panel as required to get the rebate (funded by users) from the power company. I used Unirac for easy quick mounting of the panels. Out of pocket expense was $20k after rebate and tax credit. That was when panels were going for $4.50/watt and the tax credit was capped at $2k. Now panels are more like $2.50/watt and the tax credit is the full 30%. I converted a car to electric using LiFePO4 cells last year, with range of about 65 miles mixed highway/secondary road driving. The pv array supplies enough power for our house and to drive this car about 50 miles/day, at its average consumption of 215 Wh/mile. The house has electric H2O heater, range/oven, refrigerator and separate freezer, clothes washer/dryer, well pump, furnace blower, and lighting. The array is grid tied, so we put power into the grid during the day, and pull out at night to charge the car. The array produces about 39kWh on a clear summer day and about 25kWh on a clear winter day. Our area of NV has about 250 sunny days/year. Unfortunately, NV is behind the times on time-of-use rates and feed in tariffs (and about everything else. We do not get paid for excess power generated, so everyone somewhat undersizes their array for their needs. In neighboring CA the utility pays time of use, so a friend gets 30 cents/kWh during the day for production, and does his laundry at night at 11 cents per kWh.

In Oregon the rules are that you have to hire a certified installer to get the [state&local] rebates and so it was $2k cheaper to get it installed than do it myself.. It took 4 people two days to do it, so I can't complain too much. I've had it for 2 years: every so often I look at the inverter and it says it is working, and in the summer my electric bill dips down to the connection fee level, so... That said, 2.4kw was about $10k after rebates, so payback time is a long time, at least until TSHTF. (At that point, I'll be worried about theft, so I'm not sure I'll ever make my money back.)

I've only have had one power outage in the 5 years I've owned the house, and I'm two doors down from a substation with redundant feeds, so I don't have batteries. In the event of a serious (East coast 2003 type) power outage, I'll use flashlights and the BBQ just like everyone else. They've installed advanced metering infrastructure (AMI) meters and they are working on the features for it, so in the not too distant future, in the event of rolling blackouts they'll do it on a house to house basis and they won't roll my house unless it is the middle of night or raining hard, (both of which are times when a rolling blackout is unlikely in the first place.) They can tell the meter is going backwards from the main office. The AMI already supports Time of Use rates, so I'm far better off selling the power from the solar panels during the day than charging batteries with it. If I did have batteries I'd do quite well by charging them at night from the grid and discharging them in parallel with the panels during the day, except that the solar panels already put me in the negative for daytime rates, (even in the middle of winter.)

I also have solar hot water, which has a payback of a few years after rebates. I don't know why everyone doesn't do that.


1. Is it best to work with someone who both sells and installs solar PV panels? Or is this something that people end up doing themselves, using a variety of vendors?

We installed our own 2150 watt, grid-tie PV system. We did all the planning, design, permitting and installation work ourselves, and this was a lot easier than I expected it to be. In addition to being a very interesting project, it saved us several thousand dollars. There are some safety issues that you need to be aware of for the wiring, but really not much more than house wiring.
I was concerned going in about the permitting and red tape aspects, but found all the people I dealt with from the county and the utility to be very cooperative and helpful.

The system came in just at $10K before rebates, and $6.5K with the federal 30% rebate and the Montana $500 rebate -- right at $3 per watt with everything included.

2. What brands/ types are best?

We used the new Enphase micro-inverters which puts one grid-tie inverter right on each PV panel. This worked out well, and I've been quite satisfied with the product quality and support from Enphase.

3. How much maintenance is required?

So far, it has been rock solid with no maintenance.
I have a couple solar thermal systems, and while the solar thermal systems are much more cost effective, they do appear to require more maintenance.

4. What experiences have people had who purchased solar PV, then moved to another home? Did the addition of solar PV help the resale value?

Don't know yet. It seems like around here, people are very receptive to PV systems -- I would be very surprised if it does not add some value to the house.

5. What have buyers experience with battery back-up been? Is a small amount worthwhile, even if a homeowner is on the grid?

We have a grid-tie system with no battery backup. Batteries add quite a bit of initial cost and quite a bit of ongoing maintenance. Some knowledgeable people say that the ongoing cost of maintaining and replacing batteries is about the same as what you save on electricity. If you have a relatively reliable grid connection, it seems to me to make more sense to just buy a small generator for backup and forgo the batteries on the PV system.

6. Are there any particular issues with inverters that readers should be aware of?

As nearly as I can tell the major makers of inverters have these products down pretty well. They have had several generations of products to perfect them.
One of the nice discoveries for me about PV is how mature the products are.

The biggest issue for grid-tie systems is probably whether to go with a single large string inverters for the whole system(eg a Sunnyboy, Outback, Xantrex, ...), or to go with the new micro inverters with one inverter for each PV panel -- as far as I know, Enphase is the only maker of these. It seems to me that both systems can be good.

7. If you have purchased solar PV, are you generally happy with it?

Yes -- I like it a lot.
As has been mentioned by others above, PV is still an expensive way to reduce electricity consumption.
For example, we were at 1000 KWH/mo electricity usage. We cut this to 500KWH per month at a total cost of a bit over $1K in conservation measures -- all detailed here: http://www.builditsolar.com/References/Half/Projects.htm
The PV system will knock off about 250 KWH per month more, but will cost up $6.5K to do it. So, for us, conservation and efficiency were about 13 times more cost effective than PV! Also, generally easier to do.
So, do the conservation and efficiency stuff first -- you can pay for the PV system out of the savings :)

8. Where does one find good material to read regarding solar PV?

Homepower Magazine is very good www.Homepower.com --they have a $10 online subscription that give you access to 20 years of HP -- they are very good for hands on PV.

How about my website :)
http://www.builditsolar.com/Projects/PV/pv.htm -- my site is a non-commercial site for Do-It-Yourselfers.

There is a very very detailed account of planning, designing, and installing our system here:


I think the best approach is to regard PV as a kind of 'hamburger helper' with the real meat coming from energy savings or other methods. You want to think about all the other things you can do to reduce your draw on the grid in respect of cooking, water heating, space heating and cooling, appliances, entertainment devices and so on. When you've cut back you may even find that PV is enough to eliminate electricity bills. That doesn't make you a tightwad because you can spend the savings on other things and you have prepared for when/if serious carbon taxes are ever introduced.

To give an example it seems silly to run a 2500 watt air conditioner if your best PV output is 1000 watts. You could junk both of them and get a small 150w evaporative cooler powered by the grid and still have lower bills. Do you really need a big screen plasma TV? You could sit closer to a small screen LCD TV. Same goes for shorter showers... you are not really giving up that much.

A new point I would make about PV is that cloud cover seems to work out more important than latitude. Some will say Location X is too far north or south for PV but first I would ask how many cloudy days there are. High thin cloud can cut your power output substantially in otherwise bright conditions.

Solar insolence has been well quantified in the U.S.:


Solar insolence

I beg your pardon! I'll have you know that solar energy is extremely well mannered ;-)

Let's hope so. I fear all of my hard work is vulnerable to an EMP from a massive rogue solar flair :-0

The proper term is: insolation.

Of course. I was eating a chicken wing with a poodle in my lap ;-)

Man, I've heard some slippery euphemisms in my day, but that was a doozy!

Solar insolence

Well my solar has been pretty isolent this month. Until yesterdays rain storm I was averaging 1.7KWhr day this month. The central valley is infamous for its wintertime thule fog. Yesterday It rained and it went up to 4KWhr, and todays showers left me with 8. But I'll probably be suffering from many dismal days for about the next month.

So now I've had my system for a whole 58days. In places like where I live, with a tiered electric pricing structure, it makes financial sense to partially cover your use, and quit paying for (some) power at the highest rates (.$25 KWhr or more). To cover your whole usage is not cost effective (but probably feels good). As said upthread, negawatts are more cost effective. I just purchased a spin dryer -as our electric clothes dryer is one of our big users. I suspect you can get an undersized PV system, and then if you want to get your usage to near zero, you will be very incentized to find more negawatts. At least this winter I've felt like Id like to use not too much more than the PV is producing, and rotten weather means I feel like my power "budget" is seriously constrained.

2010 should be a good year to spring for it. I think prices are still low due to the economcy, and the 30% federal tax credit is a pretty big deal.

It would be nice to have some sort of backup. The standard grid connected system will shut down if the grid fails. It would be nice to be able to bleed off just enough to maintain a marine battery or two (for emergency lights etc.) I suspect more backup than that is just too expensive to be worth it.

I'm looking at installing solar PV in the near future, partially encouraged by a friend in this region (Rochester NY area) who has an off-grid battery-backed PV system that keeps his home powered up year round even with the high percentage of cloud cover around here. He has an array of mostly newer Sanyo 200W panels. My preference is to draw power from the grid as required, but not feed back into it, to reduce complexity and eliminate potential problems for the utility (shock hazard from back-fed voltage during power outages). One goal is to build in resiliency in case of future interruptions and outages, so I want a reliable battery system. To extend battery life / maximize return on battery investment, I want to minimize depth and frequency of the charge/discharge cycles, which will involve proper battery management. Part of this will be deliberate shifting of discretionary power consumption to prime sunlight hours, and part automatic via charger management so that charge to the batteries flows from the PV while they are producing, and from the grid when they are not. I would be interested in learning from anyone who has experience in running a system this way.

My preference is to draw power from the grid as required, but not feed back into it, to reduce complexity and eliminate potential problems for the utility (shock hazard from back-fed voltage during power outages). One goal is to build in resiliency in case of future interruptions and outages, so I want a reliable battery system.

Obviously any grid tied system needs to have a DC disconnect to eliminate power from feeding into the grid should power company employees need to do maintenance on a downed power grid. Therefore if you are not grid tied this is not a concern.

It sounds like you are looking at what we in our neck of the woods call a solar generator with an inverter and a battery bank tied into a separate AC panel that runs a part of your lighting and some of your appliances. Unless of course you are powering up an independent DC circuit.

Probably the first thing you need to do is quantify how many KW hours you will be drawing and then you can calculate how many panels the size of your inverter or inverters and the size of your battery bank.

I'm sure you can find some reputable local contractor to help you with this project. If you are a DIYer then research and advice from your friend will be invaluable.

I'm also planning on a small PV/Grid battery charging system just like this, and live in the same area. It doesn't seem the be the norm, so there aren't many models to go by. Most systems are either off-grid or completely grid-intertied.

Most systems are either off-grid or completely grid-intertied.

At least in south Florida grid tied with battery backup is quite common.

My preference is to draw power from the grid as required, but not feed back into it, to reduce complexity and eliminate potential problems for the utility (shock hazard from back-fed voltage during power outages).

No offense, but the reasons you cite are somewhat misplaced concerns. On the complexity level, having two separate power distribution systems in your house is more complicated than having one, and will add to costs. As far as shock hazards for the utility workers, any UL listed grid tied inverter will reliably shut down the connection to the grid when grid power isn't present, and you will have a manual AC disconnect you can switch off just to be sure.

There are now grid tie inverters designed to be used with battery backups. The only reason I can think of not to go that route would be price. Otherwise, it does not make sense to forgo the opportunity to return power to the grid for a credit. (Although regarding that last statement, I must say I'm not familiar with net-metering law in New York.)

8. Where does one find good material to read regarding solar PV?

Having lived off grid (in style, I may add) for over a decade, if you are serious about renewables for your home I strongly recommend Homepower Magazine. You can get all of their issues on DVD for $75 (includes a 1 year subscription to the print edition). Many stories by and about folks who have taken the plunge and are living life with renewables. Issues include sections describing the technologies in understandable terms, codes, tax incentives, anything you may want to know. We couldn't have come this far without it. Includes PV as well as micro-hydro, wind, EVs, and other neat stuff. It's also a great history of the grass roots renewables movement, and a great way to know if you are paying too much, or to get in touch with vendors and installers. The best primer there is for renewables. Period.


I strongly recommend Homepower Magazine

I used to have a subscription to homepower magazine, and also recommend it as an excellent resource.


Ditto on the Home Power. I wandered through the bookstore a few years ago with a gift card and came across this magazine and have been a subscriber ever since. PV, Solar thermal, alternative building, all very energy focused at the family/individual level. More old school (no nukes, etc) lefty politics then I care for, but I think it provides humor (inadvertently) as well.

The current fed tax credit (30%) can be applied thru 2016 and applied to multiple years if you do not have enough income to offset it against. Combined with state incentives and if you live in a net metering state, these combine to offer some very attractive incentives.

One word of caution, check your suppliers and installers. This has gotten to be sort of a re-run of the 70's and a "hot" industry where some people who really should not be doing this work are doing it or tying to. So like anything else, ask for references from previous customers and call them to talk about the service they got and how happy they are. PV panels are solid state so you don't have to grease them or change the oil every 3000 miles etc. In the new issue or homepower they discuss maintenance of wind turbines and the parts about checking the wiring and nuts and bolts for the mounting system apply, but even if you were anal about doing this it should be no more than a few hours a year. Lastly, I think paying for monitoring and data logging is important and worth the expense, but I am anal that way :)

Rent or borrow a Solar Pathfinder to be sure you really have enough sun for all the seasons. It's very easy to use once you get your hands on it.

I was all over my city lot and roof looking for a good spot, with no luck :(

Here are links to the Solar Pathfinder and a place that rents it by the week...

I read a lot of books on this topic, and Power from the Sun: A Practical Guide to Solar Electricity is the best one I found:

Has anyone successfully used any kind of solar PV generator?

I already have solar heat and hot water, so my south-facing roof space is pretty much used up, and I was thinking about how to deploy an emergency-type system, which might run just a few small appliances, maybe a refrigerator, in case the grid goes down.

Essentially, my hot water systen won't function without power.

Are there any such systems out there?

FMagyar, a regular on TOD, builds and sells such systems. Hopefully he will jump on this thread and show you what he's got. I recommend that you do the math first. Decide what you need and calculate how much power you will need. A great gizmo to have is a Kill-A-Watt meter. You plug things into it and it tells you how much power it uses. Usually under $30.


Yep, I have one of those ;) Great tool !

Essentially, my total monthly power consumption is generally somewhere between 160 - 500 Kwh, depending on the time of year, averaging out at about 10Kwh per day.

We had a transformer go out in a heavy storm, last year, and power was out for 5 days. I expect the frequency of this kind of event to increase. Last year, it was in summer, so it was manageable. Cold showers are palatable in August. Not so much in November.

Primarily, I'm thinking about the feasibility of running my hot water system, furnace pump, a small refrigerator, and possibly one or two outlets with a PV generator.

Maybe I'm smoking green stuff... ;)

Maybe I'm smoking green stuff... ;)

To each his own ;-)

Primarily, I'm thinking about the feasibility of running my hot water system, furnace pump, a small refrigerator, and possibly one or two outlets with a PV generator.

This sounds like a very doable project.

What part of the country are you in? How much roof or just space do you have for panels?

Not the hot water system. It does not make sense to use solar generated electricity to power an electric hot water system. A gross waste of Exergy. Buy a sloar hot water system. It will provide, by far, the most bang for your buck from solar.

As far as the economics of the other items you will have to do the maths to see if pv makes sense.

Not the hot water system

I assume Spring is referring to powering a small electric water pump that circulates water through a passive solar collector connected to a well insulated hot water storage tank. It makes no sense to generate electricity from PV panels to run an electric hot water heater.

Most solar hot water systems offer a PV option. A dc circ pump connected to a PV panel, controller and battery would be quite affordable. Water pumping is a great application for PV.

You can probably get along without the battery, as you're only going to need your water to circulate through the system when the sun is shining. :-)

The only reason I spec a small battery for circ systems is to extend pump life. It helps on startup and reduces wear from intermittent cloud cover.

That's a good idea too. Thanks !

I didn't see your post and I've already made a general comment. Yes, we need to do the math!

The Kill-a-watt-meter is great to measure. To save money I install these:


You put these in your entertainment systems and the changes are remarkable in usage. They are the perfect kid device who turns nothing off, and even if you turn things off, they remove the vampire power by REALLY turning things off at the source.

Yep, see my comment above. If you are in South Florida my email is in my profile.

I'm in Chicago.

I'll still answer your questions but I don't work in temperatures below 70 degrees ;-)

Hey, isn't it 40 degrees where you are ? Not working, huh ?
Thanks !

To be honest I did work on a roof last week and it was cold enough for me. Mind you I have lived in Buffalo New York at one time but the blood has thinned considerably since those days :-)

We have found it practical to use pv for very limited uses-powerung electrical fences , trickel battery chargers, etc.

Many regulars here seem to be in favor of installing residential pv as doomer insurance and others as simply "the right thing to do" in terms of being a responsible steward of the earth.

I understand and respect both points of view.

But I also believe in living and planning by the odds, as I can best estimate the odds to be, and in examining the elephant from as many as possible points of view.

Pv just doesn't add up as yet-a system that would power the essentials at our house, and our house is a modest one, would cost at least forty thiousand dollars and we couldn't count on it, as our food stash is mostly in four large freezers and the farm water system MUST be up.

On the other hand I paid a little over three thousand dollars for a new gasoline powered welding machine that has built in 120 and 240 volt outlets that will power everything on the place, by shifting the load-and one fifty five gallon drum of gasoline will run it for a week just keeping the essentials running, which is the the longest the power has ever been out here-due to an ice storm.

Maybe in five or ten more years the price of pv will fall enough, and the price of grid juice will go up enough,for pv to become practical.

In the meantime, if I had the cash handy I could spend the same thirty or forty thousand on conservation measures that would save probably three times times as much energy as the pv system will generate..We have already done a lot in this respect, installing insulated exterior siding, up graded windows, high efficiency appliances, gravity powered irrigation water,wood fired heat backed up with an oil furnace etc.

When no 2 was cheap we used five hundred gallons or more in the house.Last year we used a little over fifty gallons mostly as a matter of convenience.

There are at least a dozen more things yet to be done that will save a lot more energy per dollar spent than the energy generated per dollar spent on pv at current prices.The next biggie will probably be solar hot water-hopefully the system I eventuyally install will be big enough to make a significant contribution to the residential heat load, saving some wood and or oil.

Of course if you happen to actually have a lot of money to spend on a capital improvement and are afraid tsis going to htf any day, or you just want to make a statement, you should go for it.

But if you aren't overloaded with cash maybe you should spend your money on conservation measures and put pv off for a while-the systems will get better and better , become more standardized, putting out more juice per dollar with less maintainence from one year to the next.Unless you live in hurricane counrty the odds of the power going off for any length of time over the next few years are very slim.

When was the last time you researched the price of PV? There seems to a module glut at the moment and it's been reported that prices have dropped by as much as %50 in the last few months. Just a thought..

When was the last time you researched the price of PV?

I suspect his area has cheap power. Mine makes economic sense because I figure the power I won't be paying for cost on average $.15KWhr. That is a much higher price than most regions have. My boss has a PV system at his house (marginal charge $.40 KWhr), but won't consider one at the place of business, since there it is $.12 KWhr. So if you are justifying a system solely on economics, only a few locations will likely support going to PV.

Of course if you want to get some experience, I would recommend getting some sort of minimal sized system. Then you can gather data and experience, and later decide if you want to upgrade.

We do indeed have very low rates here, among the lowest in the US.

My point still stands-for most of us the money can be much better spent on conservation.

And my secondary point, about the rapid improvement in performance and reduction in maintainence and aggravation stands too-pv has still not reached the Model T stage of it's evolution, where you can find dozens of (nearly except for the mounts and wire routing) identical systems in any little town.

I expect that as soon as a few more patents expire and the volume ramps up considerably the accessory equipment such as the mounting racks and inverters will decline very fast in price.

More than likely -if we see the regulatory authorities do the right thing, which DOES happen occasionally,we will see performance and installation codes and standards enacted which make the systems essentially generic in nature.

If I need hardware to repair or expand the wiring system on our farm , I can buy stuff that works perfectly and interchanges perfectly from dozens of sources and lots of different manufacturers.Consequently anything I might want is relatively cheap-there is no way a manufacturer or dealer can hold me up for several hundred dollars for a part that cost five or ten bucks to make.

For instance I had to buy a new forward / reverse shifter switch for my backhoe recently-this extremely simple switch , which has only four or five ounces of plastic, an ounce or two of copper wire ,and a very small spring and four contacts in it cost three hundred dollars.It is generic in nature as to how it works but not in the way it attaches to the machine, and no aftermarket is available due to low volume.

I can buy an electric drill which is far more sophisticated and has more , larger, and heavier components for forty dollars-because the drill is not a "dealer only " item.

Once things progress to the state of affairs to wich I refer, any competent electrician will be able to quickly and accurately diagnose a problem, more than likely fetch the needed part out of his truck and have you "humming " again on short notice.If he doesn't have the part , it will be available at any local electrical supply store and will not have to be shipped across the country.


My priority list, which is roughly in order of payback analysis:

1. Finish remaining household energy conservation/efficiency items.

2. Install solar H2O heating system

3. Install solar space heating panels (will not be enough to completely heat house by themselves, but will help)

4. Acquire batteries, inverter, charger, and install swiching circuitry so I can provide backup power for at least 1 week to refrigerator, freezer, HVAC and water heating control systems, a couple of lights, and just a few other high-priority items

5. Acquire and install sufficient PV panels + controller so that battery bank in item 4 can be kept charged by solar alone most of the time (I can take my chances with the occasional exceptionally overcast week here and there - the odds of that coinciding with an exceptionally long power outage seem very slim)

6. Acquire additional PV panel capacity so I could recharge an NEV's batteries

7. Add more backup batteries and PV panels to cover lesser-priority circuits and devices throughout house

I don't know if I'll ever even make it as far as #7. Somewhere in there, too, needs to be trading up to a larger wood stove, but I haven't done even rough estimates on the payback period for that yet so I'm not sure where to place it. It is probably closer to #5 or 6 than it is to #1 or 2.

I don't know if this same exact list would apply to everyone, but the underlying methodology probably does. THINK IN TERMS OF PAYBACK PERIODS, PEOPLE! Payback is your friend, it is an easy way to reduce these decisions down to an apples-to-apples comparison.




Here's our set-up. We have a dozen Trojan L16RE batteries, and two Trace 4024 inverters. Added solar
water this past summer. Some of our circuits are still on the grid, i.e. elec oven, dryer, heat/air.
Both our 220v water well pumps are on the solar/wind system. In the mid 90s we were w/o power for
11 days during an ice storm. We couldn't flush the toilet or water the cattle since we only have
well water. At that time we started accumulating the parts for our system. Our grid bill is about
100 per month-- or less during the fall & spring. I put the photo link 'cause I didn't know how to paste it in the message.

Nice sky!

Re: pictures there is a section in the FAQs

How do I include an image in my comment?

* First, you must upload your image to a web-accessible server. Several image hosting services, such as Photobucket and Flickr provide space for free.
* Then include the appropriate HTML code in your comment. For example:

BTW that last line is an image not text

In photobucket, open the picture you want. On the left side is a list of link choices. Click on the html link bar and it will copy the correct link (to your clipboard). When you want to post it on TOD, just left-click and hit paste. html will do the rest.

I have a wind turbine and solar panels – grid tied. I've had it in place for a few years now.
Almost anyone can understand the fundamentals of a solar panel stuffing electrons into a battery. The less obvious part is learning what instruments you need to test things, how to interpret the readings you see, and how to act on that information. Be sure that your installer has a detailed users guide and you have an arrangement for contacting him for assistance. Note that the manual for an inverter is NOT a users guide, you need to know how to set up a schedule for running from the batteries periodically, when the batteries are reaching a critical state of discharge, how to hook a gasoline powered generator to charge batteries when there is no wind or sun, schedule and record checking and topping up the water in the batteries, and how to determine how much power your system does actually generate.

Some brands of components include monitoring and data logging built in. I use Outback Power Systems charge controllers and inverters. I also have two older Trace 4024 inverters (Trace is now Xantrex. Outback was formed by former Trace engineers when the company was sold to Xantrex.) Both the Outback and Trace/Xantrex can be monitored/logged by PC connection. Three of my arrays on a hazy day:

PV output 01-01-10

my advice is to wait. wait for price drops (chinese panels). check into gov rebates. the fed rebate is easiest. state rebates have waiting lists and restrictions. i have a 3KW PV system. i paid $25,000 for it. it was the year before the 30% fed rebate. my state rebate at that time had a 3 year waiting list. my advice is to get a 6KW system. there is no maintainence on a solar system. once it is up it is problem free. i had 2 bad inverters. the third seems to be a charm, all on warranty replacement. it is a grid tied system. no grid no PV.

i had my house appraised to sell back in august of 2009. my house still lost 30% of it's value from 4 years ago, that is $100,000! the PV system added no resale value. did not list house for sale. as i did not take my state's rebate the system is mine. if i move i can take it with me. if i took the rebate the system stays with the house. am i satisfied? not sure. you have to pay out the full install price up front and wait for rebates.

do i "save" electric? yes, but not enough. i get "free" air conditioning in the summer. i live in a temperate zone. i find the $3000 i spent installing a wood burning stove was much more cost effective. the stove has already proved itself more practical (comfort and energy savings) than the solar system. stoves have lots of maintainence. the stove added no resale value to my house.

i live in nj. nj offers energy credits to people who install alternative energy. i retired my energy credits as a protest to the way the system operates.

one last thing. i tinkered up some portable solar power generators. they can be seen at:

Related question: any input from those using solar powered water pumps? I can deal without electricity for a long time but would miss the water! Is it cost efficient to use it full time instead of electricity? In my part of the world I've been looking at Robison Solar Well Pumps: http://www.highplainsgreenenergy.com/products__services Thanks.

We use solar to pump our spring water. We have 2 80 watt Siemans panels on an old Zomeworks passive tracker I found on a junk pile (works great), hooked through a contoller to a SunPump. The water goes to a tank on the ridge above the house and gravity does the rest. The problem with solar well pumps is how to store the water/pressure when the sun doesn't shine. Water pumping is one of the most prevalent uses of PV.

If you want to Maximize daily H2O out of the well with the least power (often lowest system cost) , A Grundfos SQflex is the way to go.
You have to select the one for your pump head.
One of these with 2-200w class panels will pump enough H2O for a small village.
A game changer in terms of Population of African Villages.
Donald Long

I also recommend Grundfos gear, although I haven't had experience with the SQflex.

We installed solar PV one year ago and are now able to tabulate a year of results. The contractor we used installs only Sunpower systems, so that's what we have. The contractor was reputable and did a good job with the installation. The cut-over and the sometimes annoying city inspection process was painless on our part. People keep asking me how I like our PV. Well, they just sit up there making electricity. Silently. Nothing to notice. You don't have to do anything except read the monitor occasionally if you want to see how many or how few kilowatts they generated that day. (The monitor is on a wall in our kitchen so we don't have to run outside to look at the meter.)

We calculate after state subsidy, city incentive and federal tax credit our system cost us around $12,000. We had it installed just after we replaced the roof on our house. I have no idea how it will affect resale as housing prices are dropping here pretty wickedly (after truly silly highs), but I notice these days about 10% of my neighbors also have PV panels, so they are going mainstream and may soon be an expected part of one's house.

Our system is 3.0 kilowatts with fifteen panels. The roof of our house breaks east/west, so 7 of our panels face east and 8 face west. When the contractor gave us our original quote, he estimated that our system would average 11.1 kilowatts a day. He was conservative. Last year, over the twelve months, it averaged 12.2 kilowatts/day. This is in San Francisco where we get our fair share of fog, although we do live in the sunnier, eastern half of the city. In June we average 18.2 kilowatts/day. There is a lot of variability. Our best days have been around 23 kilowatts; our worst day a measly 1.5. If we had a south-facing roof, our system's performance would undoubtedly be better, but so it goes.

We do not have a battery back-up. If our power company becomes unreliable, I may consider it. We feed power to PG&E when we produce more than we use. During the summer, if we keep power usage low during peak periods (1pm - 7pm) we can sell electricity to PG&E for $.29 a kilowatt. Partial peak rate (10am - 1pm, 7pm-9pm) we sell at $.14 (or would buy at that rate if we used more than we produced.) Off-peak the rate is $.08/kilowatt. So there is a big incentive to run laundry, dishwasher, etc. off peak. Our "true-up" period with PG&E is an entire year. So the excess electricity we produce in the summer can be used to offset the electricity we buy in the winter. This year, our net purchase of electricity came to about $10. We are also charged a monthly fee for the "privilege" of being hooked up to the grid. We also, as of now, can't sell back more $ than we use--i.e. PG&E will not pay us money if we sell to them more $ worth than we buy from them. I believe there is a law the governor signed recently that may change this in California so that solar PV owners will get paid for all the electricity they feed into the grid.

As I said, our average electrical production/day last year was 12.2 kilowatts. Our family's average electrical use/day last year was 14.94. So our solar PV did provide the majority of our electricity. We added solar hot water in December (the worst possible month performance-wise) which has converted our main hot water tank from natural gas to solar with electrical back up, which may up our electricity usage significantly in winter months. I'll have to let you know later what kind of performance we get out of it. I would like to lower our electrical usage back down by converting CFLS to LED bulbs as the technology improves. (I wish someone would make an energy efficient candelabra bulb that didn't look as ugly as a Dr. Who dalek.)

There are a variety of gas water heaters suitable for solar back-up. They need a sensor to measure input water temperatures.

My biggest concern is the minimum heat levels, "warm" solar water may trigger supplemental heat and then drop below the minimum, creating a step function in temperature :-(

Overall, the energy efficiency of tankless gas hot water heaters and solar with electric back-up is generally minimal. Solar with gas back-up is the way to go.

Note: Tankless gas requires larger gas feeds and higher grade flues than gas tank water heaters.

Best Hopes for Efficiency,


Philips makes a nice LED candelabra bulb, plus some excellent R20 & R30 LED spots. These lights have a very pleasant 3200K color temperature. Home Depot carries them here in the East.

Here are some real costs I pulled up in response to a post from Scotland last night regarding a system for charging an EV. Add another inverter and you would have a nice off-grid system (or grid parallel system) if you are handy enough to do the install. Just an idea of component costs today.

If you figured $30,000 for 3120 watts of panels you guys are paying about 2-3 times what we are in the U.S.. I can get a pallet of 28 200W panels for under $2.50/watt. (5600 watts = $14,000) Looking at top rated Kyocera 210W at $3.11/watt ($706 each). $12,708 for 18 panels = 3780 watts (rated). An order that large will probably get you free shipping in the lower 48. Depending on voltage, charge controllers would be less than $2000. Rough figure for good batteries (about 42 KwH) and a good inverter about $9000 max. Balance of system, $1000 (not including panel mount).
Grand total: $24,708 (and with some arm twisting even less). I just wanted to give folks an idea of what a good system for charging an EV in the U.S. may cost. Around $25,000 (plus install and mount) will charge your EV for years and provide a good backup system for your home. Panels are at historic lows in the U.S. right now. I'm sorry to see they're so high across the pond. Maybe you should shop around some.

Edit: found same panels for $628 (Kyocera KD210GX-LPU 210w)


They have the Schott ASE-300-DGF (290W) for $1157

Thanks for doing the research Ghung, and thanks Gail for this separate article on the subject. It is interesting to read about practical experiences of implementing PV (I have a background in electronics). Alas, I suspect my home is at too high a latitude and too poor a climate for PV (plenty of wind for the local wind farm though), but it's certainly informative seeing how it is being implemented in warmer climes.

Higher latitudes are great for PV in summer, especialy if you use a tracking mount. With the long days at higher latitudes, tracking arrays can produce amazing amounts of power.

Kyocera KD210GX-LPU 210 Watt Solar Panel
$605.00, 20 for $11,640.00

Northern Arizona Wind and Sun

These prices from NAW&S have increased since the minimum in October 2009.

I have a new solar array from last summer. One thing I did not think about:

If you live someplace snowy, don't forget that the snow can slide off the array all at once because the panels are slippery enough to let it get some momentum. I'll probably need to add some sort of barrier at the bottom of my roof to prevent the snow from crashing down like it has.

In Australia there has been a strong takeup of domestic grid connected pv over the last year. This is primarily driven by government incentives. Basically the government will subsidise around 50% of the installation costs. In addition our state governments have decreed that owners of small pv systems can earn an inflated feed in tarif on the net amount they feed into the grid each month/quarter. The feed in tarif varies from state to state but is around 3 times the domestic electricity tarif. Based on these incentives, in some cases it makes good economic sense to invest in these systems.

Unfortunately, there are a number of installers that are manipulating the truth when selling these systems to home owners. Two of the scams I have noticed are:
- sellers pretend that a 1 kW system will provide approximately 1 kW of power to the owner on a continuous basis. When pressed they will conceed that the system will provide less than this depending on weather conditions etc.. the reality is that a 1 kW system will actually only provide around 1800 kWhr per year depending on location etc.etc.
- the feed in tarif will only apply if the household produces more than it consumes on a monthly or quarterly basis. For normal household it is unlikely that they will get any return even if they install a 2kW system.

I am sure that most of the reputable pv system providers don't lie about these facts but I know they are very careful with the truth.

I see battery back-up as insurance. My solar installer actually tried to talk me out of it, but I insisted. Modern life pretty much comes to a halt when the electricity goes down.

Here in the Santa Barbara area we had several power outages caused by brush fires. The battery backup system automatically kicked in -- and we were quite the envy of the neighbors sitting in the darkness.

Blackouts of several days, weeks, or months (given a major earthquake, major system meltdown, etc.) will make you kick yourself for not having battery backup.

By the way, the batteries are re-charged by the solar system during the day, so a blackout could last for sometime before the batteries give out.

Here in the Santa Barbara area we had several power outages caused by brush fires. The battery backup system automatically kicked in -- and we were quite the envy of the neighbors sitting in the darkness.

Gasoline powered generators can be had quite cheaply. I woulda sprung for one, but if you keep gasoline around too long, it goes bad. And we haven't had a long enough outage since they replaced our crappy distribution transformer. So one alternative would be a polluting, but cheap fossil fuel fired generator for those just in case periods. I suspect that could save some serious bucks on batteries.

In fact at work they have a fancy UPS. Batteries only cover a minute or two -until the diesel generator can kick in.

Well here we go. I'm sure I'll get flamed for this.

PV does not, does not, does not remotely pay for most applications. I've lived with PV exclusively(that means no backup at all) for a decade on sailboats before my current project. My sailboats had no auxiliary propulsion other than sail(and a big oar)and there was no way to cheat. My demands were extremely minimal--I'd run electronics and a boomer stereo(not a purist, mind you.) We're looking at a system that costs probably 2 grand to supply the demands of D cell batteries reliably. That's expensive, but was the only game in down. It worked.

Here in Hawaii, I've just installed for a friend a 1 KW array, which is very small, and his demands are very small too. We've got a drought right now so it's been cracking out the juice like crazy. I've a lot of respect for the OUTBACK gear in general, and probably wouldn't go with anything else. My boats, however, were 12dc and direct wired with big batteries and charge controllers were me with a toggle switch. The 1 KW array is a 10 grand project at this point, having just finished one to DOD specs.

My Honda EU 2000 here in Hilo Hawaii was 1100 bucks with tax. It burns a gallon a day if its also running a hot water heater. It will run on papaya E90 just fine. I've got a far far better chance of keeping the Honda running and getting parts than I do trying to electo-flux bad cells or fixing the guts of a high tech inverter. Tearing down the generator or even rewinding the alternator isn't that intimidating. The alternative is impossible. PV is a completely non-renewable renewable at this point.

What's more more sustainable? The generator, easily, and by a lot. We haven't discussed batteries. I'd much rather store power in a stable form(E90 or better) than try to keep a 3000 dollar battery bank charged. Really, I don't think there's any other way to spin it.

A bit of a diatribe, but I stand behind it if you crack the math on an individual level.

For those looking to purchase--here's a tidbit of advice. It's really hard for someone having dropped 20k on a system to admit whether it works or not. If you're looking for advice, limit your input to those who have lived on PV exclusively(no grid or generator backup.)Don't get me wrong. PV works. If it's the only option, it's a great option. In my experience, does it make sense or is it sustainable? Hell no, would be my response.

Just another perspective, Jay. In 13 years we've gone through 3 generators. The original 840 watt array hasn't been touched except for cleaning and an upgrade to wiring and a MPPT controller. The old contoller is still working in an RV. We have 34 panels total and have yet to have a single failure. No oil to change, no fuel to buy. Off grid, a genny is pretty much a fact of life but I sure don't want to listen to/smell one most of the time, and I wish my generators had been as reliable as the PV systems. I agree that, if your goal is to keep things running during a temporary grid outage, a generator is the way to go. Big box home stores sell natgas standby gennies for less than $3000.

BTW, I've seen some nice wind generators on sailboats.

Hi Ghung ,

You must have bought some pretty crappy generators or else you must have put a LOT of hours on them.

I have a 5000 wattt Yamaha that has seen extensive use for twenty years as we use it when we have an outage(seldom over a day here) and also for many varied jobs out in the field, including an occasional paid job putting up a barn or oter structure off the grid , wich is common on the farm.

It has yet to let us down other than having to clean the carburetor and gas tank.A long time ago I decided that you are making a serious mistake when you buy any small machine such as a generator made anywhere other than Japan.

Genuine industrial American equipment is fine, but you will find that at dealershps where only professional trades people do business.My big generator is a Miller welder and it is utterly dependable.

The problem with American is that the marketing people like to sell homeowner quality for commercial quality.I expect a good many regulars here are acquainted with small engines optimistically labeled I/C for industrial /commercial.

They are actually pretty good little engines, fine for the price, but they are not built to last in constant use.

As an aside, I would not put much value on a thirty year warranty unless there is a financial bond of some sort associated with it.Most small businesses don't last that long, and most of the companies currently producing pv will more than likely fold.A lot of producers will be bought out and records will disappear.A second or blemished unit bought thru back market channels may work fine and the warranty might be honored-or it might not.I've been there and done that with other products, and my results are mixed.Furthermore this involved warranties that extended for twelve to twenty four months.

The odds are probably pretty good that we will be involved in a trade war or possibly a bullets and blood war with China in a lot less than thirty years.

Hi Mac. I'll comment on PV manufacturers first. The panels I buy aren't from small upstart companies. Just to drop a few names: Mitsubishi, Sharp, Sanyo, GE, BP Solar (formerly Seimens America), Kyocera, Schott, Unisolar, all heavy hitters. There was a comment earlier that solar systems haven't even reached the Model-T stage yet. Wrong, folks. This is mature technology, PVs preceded PCs. Much of the equipment is made by major manufactures of consumer and commercial equipment. And names like Outback, Xantrex, and Fronius are well respected for quality and inovation. Have been for years. I would worry more about a warranty from GM than from most of these guys. But you are correct. 30 years is a long time.

As for generators, most air-cooled engines these days have life expectantcy of 500-1500 hours. My first genny was a Northstar air-cooled diesel from NorthernTools and lasted about 200 hours (after being repaired twice). They finally admitted it was a lemon and gave me a duel-fuel that sucked a valve at around 500 hours, destroying the engine. I maintain things religiously, so it wasn't my fault. My next genny was a Generac propane that had issues from day one. It has had 2 voltage regulators, broken manifold bolts, fuel pressure problems, more. The people I got it from have stood by it, but their tech admitted "they ain't buidlin' 'em like they used to". I still have this one as a back-up, but it's on it's last leg. 633 hours on it. Note: none of these generators produced close to their rated output. I used these generators to build the house (along with PV) and they were never run really hard, maybe 60% load, on average.

Our current workhorse genny is a watercooled Mitsubishi diesel, 11KW, and the engine has an expected life of over 15,000 hours. I've had a few problems (fuel pump relay, air cleaner mount) but nothing major. It produces clean power at near its rated output and sips fuel, so I'm a lot happier now. We're putting about 300 hours a year on it so hopefully it'll last a long time.

Luv hearing about all these installs and experience - almost as good as
reading HomePower. But ... no doubt, future experience will be very positive.

Panels: My Memory is failing me, perhaps it was
Solarex -> Siemens -> Shell -> now Solarworld - 100% US Made.
Or was it Solarex -> BP
Current Panels - Just Think - ONLY 4 - 240 watt class watt panels is
flirting with a kW peak!

I'm disappointed with the 2 main Hybrid Inverter suppliers:
Xantrex and Outback right now for "future installations".
Xantrex seems to have abandoned the single phase
market now that they are Group Schneider to focus
on Big 3 phase Iron, Outback does not have a Split phase (240V)
solution except with 2 or more Inverters.
I'm replacing some Xantrex gear with Apollo next week.
They have a High Voltage Charge controller that can be use
for Battery Backup with some clever parallel wiring with a HV Grid Tie system.
Apollo Solar was awarded a Fed grant to develop
a Grid / Hybrid Setup. These guys know super efficient and reliable power
electronics, Can't wait to see a hybrid product
from them. A hybrid Inverter will do both Grid Tie
and Battery backup.

The SMA Sunny Boy / Island is the most
modular/flexible hybrid solution for mid size systems and up.
You can build independent community micro grid(s). You can add
more Renewable AC OR DC power incrementally onto your "Local Grid"
at any time. Sunny Boy's will be made in the USA Q2 2010.

I think PV is a great Investment now, The Products and trends I saw at the Last
Solar Power International Show were truly innovative. MicroInverters
will be a disruptive technology. New and exciting PV products are in the
pipeline. Grid Parity is here for some NEW power plant
construction in some climates ( which is how much per Kw ?? ) .

BUT, It will take a FIT to make Solar Power Happen. IMO - Tax credits are/should be
history. Incentives must be production based. A power meter is not corruptible.
Brand new Web Site to Track Progress in FIT's - Feed In Laws.


If the grid was free like piplines are,
my neighbors and I would start on our megawatt barn ...post
haste, even with only minor incentives.

Donald Long: Pensacola FL.

I think you're right, Solarex>BP, Siemens>Shell. I've heard great things about Apollo and Sunny Boy is probably the best selling grid-tie in the world. They must be doing sumthin right.

Hi, Ghung

I didn't mean to imply that pv is at the Model T stage of DEVELOPMENT, that was careless on my part.You are absolutetly correct of course that there are MANY reputable manufacturers out there.

I intended to refer to the Model T stage of market penetration by a given manufacturer , when parts will be available in every little town and even the high school dropouts who repair cars will be able to trouble shoot and repair the system.You will have a nieghbor who can help you fix something at that point and probably won't even need a technician most times.

At one time we had MANY automobile, truck, and tractor manufacturers too.Most of them are long gone now.

I expect the same thing to happen in the pv industry-and any sort of serious international up heaval might mean the end of support from a manufacturer located in the wrong place.

I'm a rolling stone as I've said before -and I have professional experience in the small ice field including factory service tech certs (expired) from three major manufacturers.You should simply never buy a store branded engine unless you can tell with certainty who the manufacturer is -these chains like northern handle mostly junk-not that junk can't be a pretty good deal sometimes.

For instance if you need a generator and have to rent one for a day-assuming one is available -it will cost over fifty bucks for a day in addition to the aggravation and road time.Since the typical day involves only two or three hours of running time if your are doing a project or a tradesman on a service call the junky generator can pay for itself very fast indeed and you tie up a lot less money.A machine that lasts a only couple of hundred hours might pay for itself three or four times over as compared to renting not to mentin the time and expense of pickup and drop off involved in renting.

I've never met anybody who owned a Generac who was happy with it if he counted on it.If they aren't bankrupt already I expect they will be before too long.

A used Honda or Yamaha or other major Japanese make bought second hand in good condition is a far better deal than a new el cheapo from a chain store.

One local farm store chain is junking Chinese equipment and giving new machines in order to last out the warranty.Once the warranty is up , the machine is worthless at the first breakdown.Any mechanic who works on the first one will never allow asecond one in his shop-you simply cannot satisfy the customer when you can't get parts.Some of these non repairable off road utility vehicles sell for four grand or more.

We had one guy a year or two back who set up and sold scooters in three different towns around here-VERY pretty scooters that last on average less than six months before they need a part that simply can't be had.

Some irate customer will probably shoot him someday.

About your little diesel-I really do think it will last a long, long time. But I have seen quite a few of them fail in a very serious fashion, even the best brand names,at three or four thousand hours.

I don't know of anybody yet who has gotten as much as ten thousand hours out of such a small late model design diesel-they run at higher rpms and have much lighter components that the larger engines used in heavy duty applications.I'm not saying some of these engines won't go past ten thousand hours-not many people put enough hours on them to know yet.The ones that I have seen fail were in forklifts that are used almost every single business day and even then they seldom run over twelve to fifteen hundred hours per year, usually a lot less.

Farmers around here swear by thier Kubota tractors -until they get three or four thousand hours on them -then they swear at them when they find out how much an engine rebuild is going to cost.We can't afford new tractors so we recently bought a Ferguson with a forty horse Perkins diesel which I expect to last at least 6000 hours.Ten thousand is not out of the question but probably not without an overhaul.Max rpm is only 2200, and most of our work done at 1500 or so.

Of course the big diesel engines built by the old line manufacturers will often run for ten or fifteen thousand hours without a rebuild if well maintained, sometimes much longer.

The diesel engine in my 1982 Mercedes Benz 240D stayed in production for over a decade after the last car was built for the marine and refrigeration applications. M-B 4 cylinder engines were common on refrigerated trucks to just run the refrigeration. Different camshafts and some detail changes, but same basic engine.

I heard a Japanese manufacturer took over the reefer applications (Isuzu ?).


One other thing than meticulious maintainence is extremely important in dteremining the life span of any good engine-this is the pattern of use.A motor that is started up and run properly eight hours or ten hours per day , will probably accumulate twice or three times as many hours before it needs a rebuild as one that is used intermittently for a few minutes or a few hours, subjecting it to a lot of cold starts.Cold starts are engine killers,but otoh letting them run unnecessarily will kill you for fuel.

Anoter thing about older engines that may still be around and in good condition is that until the advent of computerized everything, manufacturers were not able to build so many variations of the same item.

So if some company wanted an engine for a certain job , they probably had to buy one already on the market-and the only ones on the market were good sturdy models made by old line companies.So a brush chipper that would be sold to a small contractor might have a true industrial engine on it.

Nowadays there are plenty of junk engines manufactured as Ghung points out that probably will last only a short while, say five hunderd or a thousand hours-which might be enough to go twenty years on a homeowners generator or a brush chipper or a little used garden tiller.

The problem is that these engines get crappier and crappier as time goes on and people buy on the basis of advertising, easy credit, etc, rather than long term reputation.

And something I failed to mention somewhere else in this thread-

Good companies have a way of being chewed up for thier juices and thier carcasses spit out these days by takeover artists and inside corporate managers both.If you talk to an older trades person who uses expensive tools he will tell you about brand names that used to be old standards which are still on the market for homeowners.After these companies change hands a couple of times you can generally kiss the possibility of getting parts for your older top quality drill or air compressor or generator goodby.

Just because a particular brand x is still on the market in fifteen or twenty years from now is no assurance a warranty will be honored.My guess is that extremely few dealers and installers put thier PERSONAL written gaurantee on thier systems for more that maybe three years or so.

I can think of three brand names right off that I don't buy any more that have gone this route.

My genny has the Mitsubishi S3-L2, 3-cyl which along with the S4-L2 is deployed all over the world in many applications. It's very poular in marine applications and used in a lot of small commercial stuff like skidsteers. I use only synthetic Rotel, changed about every 150 hours. It usually runs several hours at a time for charging batteries, in a steady state. Enclosed, it weighs in at just under 1300 lbs. so it's not light duty. One can always hope!

Given the use pattern , the synthetic oil,frequent changes,and manufacturer you have an excellent shot at your engine living well past ten thousand hours.It might even go close to twenty thousand hours.If it belonged to me I would put a new water pump, belts , and hoses on it every five years max and change the anti freeze every year two years max.

Fresh antifreeze means a fresh charge of corrosion inhibiting chemicals in the cooling water.You should never ever ever run just straight water in the cooling system even if you live in a place that freezing temperatures are out if the question.Furthermore good antifreeze contains a water pump lubricant and also helps protect against overheating by raising the boiling temp of the coolant.

Such an engine is well worth the installation of automatic over heat or low oil pressure auto kill options or accessories. If you have these options you can leave the water pump on it indefinitely.

One handy hint from somebody who fixes a lot of stuff-If you own an expensive machine of this sort, buy yourself a mechanics stethoscope-a ten to twenty dollar model with a known brand name is adequate.When you apply the probe to an engine or generator you will hear amazing sounds.It will come in handy a lot oftener than you would ever guess if you fix stuff and also makes a fine toy for kids old enough to handle it safely.

If you will take a minute or two to listen to your machine each time you service it, you will soon learn to recognize any change, and usually well before it becomes audible to the unassisted ear.

There will be no question as to where a new whine , squeal, click, tap, or thump is coming from.

This cheap tool will greatly simplify trouble shooting but more importantly it lets you recognize trouble before it gets out of hand.

For instance a slight hammering fast paced noise might be a rod bearing fixing to let go.If you shut the engine off immediately it can usually be economically repaired .Let it run a few hours and you will at the very least have to buy a new crankshaft in addition to new bearings.More han likely you will find that if the rod comes loose you will need a whole new engine.

Any engine worth over a thousand dollars is worth the installation of oil pressure and water temperature guages.Any change in the gauges needles normal hot position is cause for investigation.When an engine starts accumulating a lot of wear the oil pressure generally starts to fall off -once it approaches the specified lower limit an overhaul is indicated but the engine might still run for a very long time before it fails, maybe several more years in intermittent use.

What I can share...

In California, the solar industry is already pretty mature, IMO. The rebates are complicated and so the solar installer walks the client through the process. Different jurisdictions already are developing their particular solar code requirements. Contractors seem to be able to get a substantial wholesale price advantage on modules. For the three reasons just stated, DIY is generally not the way to go for anything but small off-grid applications.

Storms are not a big issue in cities here, so for the time being people are not concerned about the grid going down, and battery backup would be rare except in rural areas. taomom's experience is probably the pretty common for people who've installed solar recently. Around here, getting a good deal on solar is becoming like getting a good deal on having your house repainted or your roof redone; It takes about as long, and the hard part is finding a solar contractor you can trust.

After I pushed my parents to install solar for a while, a neighbor of theirs suddenly started pushing for a group of homeowners on the block to install solar. They were offered a substantial group discount (~%30, I think) by an installer that focuses on residential systems. (This may tell us something about how much of the cost is profit for the company owner.) My parents have now had their 2.1 kW system for about three months, which is too soon of course to posts results, but I'll be keeping tabs on it.

I'm a PV holdout here. Prices keep falling and a PV system could depreciate faster than the savings.

Also there is the issue of highest return on investment: light colored roof in hot climates (painted metal, not asphalt or rough material), good quality windows, extra insulation, high efficiency HVAC and appliances. The cheapest thing is smart house orientation. Have overhangs that shade in summer and gather sunlight in winter. It takes a lot of expensive retrofitting to make up for bad design.

Also, how many square feet do you really use?

'm a PV holdout here. Prices keep falling and a PV system could depreciate faster than the savings.

Also there is the issue of highest return on investment: light colored roof in hot climates (painted metal, not asphalt or rough material),..

Can't disagree with those concerns. The future price trajectory could be an issue. I gambled on the recession discount being great enough to make the market risk reasonable. But YMMV. I wish I couls paint my roof whiter, but homeowners assoc etc. make that a no go. I get a lot of insolatiob based AC demand (we can easily get a week of 105day 80night). Before doing PV I added a radiant barrier (AtticFoil.com), and added some attic insulation -plus some reflective film on some problematic windows. I'm hoping the roof shading from the PV panels will further decrease the thermal load. I ain't at all a DIYer, but adding a little extra attic insulation takes almost no talent.

Also don't neglect shade trees. I've put in a bunch to cut down of summer morning and evening sun on the walls. Of course it will take a couple of years before they grow enough to make a difference. Like my roof, I'm not allowed to change the color -otherwise true white paint would cut outer wall temps a lot. Ive measured my off-white walls at over 150F, so shade and/or a highly reflective color would make a big difference.

Since two members of our household have medical equipment which needs powered, I snagged about 1kw of panels which are still boxed up, and some batteries I keep a trickle-charger on, just so I could get them up if I need to. We'll see if I ever do, but I decided not to take for granted that I could always get them.

Hawaii near sea level doesn't really require much energy for anything, though it is nice to have a fan blowing on a muggy day. I have a couple of second-hand 75w panels that i just throw on the roof to power DC fans directly. I'd like it if I could do the same thing with an inverter and my 110v fans without a battery involved, but they don't seem to be built for it.

Indeed, I like the notion of PV-powered things without the batteries, that run just when the sun shines. In addition to fans, I run a circulation pump in our pond that way. I wonder if there are other battery-less and even inverter-less uses? I think I heard that SunDanzer made a refrigerator that runs with direct connection to PV, but I may have hallucinated it.

A small system for charging device batteries would seem to be a good idea for almost anyone; the difference between "no" electricity and "some" electricity is a big one.

I've lived off the grid for 26 years. If you're completely off the grid and on batteries then I'd strongly suggest that you have the lights that you use most often be either 12, 24 or 48 volts (whatever your battery configuration is) so that if your inverter shuts down YOU STILL HAVE LIGHTS THAT ARE DIRECTLY POWERED BY YOUR BATTERIES. We have solar during the summer and hydroelectric on a small seasonal creek during the winter. During the fall and spring when the days are short and/or overcast and we haven't had much rain, our inverter shuts down whenever the battery voltage drops too low. Since we have 12 volt lights we aren't suddenly sitting in the dark. If you completely depend on your inverter and only have 120 volt lighting, whenever the inverter shuts down your lights go out too.

Since the advent of the 'Daylight' (Blue-White) LEDs, it's been nice to have a cheap, low-voltage way to have some Non-Yellow lighting available, too. I've built a few panels of these that hang above task areas, and one gets the feeling that there is a skylight above you. Kind of nice!

I also find that the blue-white, while tiring after a while, is still a great source in deep darkness. Just one little LED can be enough to read by or get around with, so it requires just a whisper of electricity now to have some essential and usable light available.

Solar has for a long time now had the reputation of being marked by Dim Yellowish Homes where you couldn't really see properly at night.

Jokuhl wrote

I also find that the blue-white, while tiring after a while, is still a great source in deep darkness.

Whoa! There are health issues with blue LEDs that also have implications for blue-white LED light. Think "macular degeneration". Read this thread.

grayfox - where do you get your 12 volt lighting?

So what prices are we down to (for panels) ? $/watt delivered ??

what is the minimum Whr/day/person(or household) that is being lived with ?

I've seen panels advertized for less than $2.50/watt. You can get "blems" with full warranty and output for less. Shop around.

Evergreen 205 watt blems for $2.79/watt:


I usually have gotten free shipping on large orders. Be sure to check deliveries. They get broken in shipping sometimes.

http://solarbuzz.com/ gives you a good indication of how prices are going with graphs

e.g. http://www.solarbuzz.com/ModulePrices.htm shows the prices since December 2001 and latest prices, e.g. "...The lowest retail price for a multi-crystalline silicon solar module is $1.98 per watt (€1.39 per watt) from a US retailer. The lowest retail price for a mono-crystalline silicon module is also $2.70 per watt (€1.89 per watt), from an Asian retailer...."

The last two years for Modules, Inverters, Charge Controllers (Regulators) and Batteries.

For 10 years I lived with PV panels outputting ~1.8 kW·hr / (sunny day). I only used a generator a few times to recharge batteries. The refrigerator / freezer used propane during that time. In 2001 I added a PV panel increasing the power to ~2.3 kW·hr / (sunny day) to partially run the refrigerator / freezer from electricity reducing propane consumption. Last year I expanded the PV system to ~3.0 kW·hr / (sunny day) to run an all electric refrigerator / freezer. I have almost eliminated my propane consumption relegating it to unused backup for heating, cooking and refrigeration.

I researched a while back to install PV on the roof. Decided finally that it was not worth it. Instead I enrolled for "green power" - my utility promises to buy green power to the extent I use electricity. This adds about 10% to my electricity bill.

BTW, here is a very useful link.


You can input your zip code and the amount of electricity you want per month from PV. Using solar insolation etc. it will calculate and tell you how much PV to install and how much it will cost etc. The price of $8/kwh is a little high - but in Seattle to get 500kwh / month, this is my cost - $43K ($28K after incentives).

Nice calculator. I just ran the numbers to generate 500 kwh/month (50% of our usage) for our house in Seattle.

Payback time = 35 years.

I guess I better keep looking a conservation measures.

-- Jon

Well, I've been accused of thinking small, but considering our energy future, that may not be such a bad thing.


This homebrewed little PV- Palm Computer is my answer to the venerable Solar Calculator, using the panel left over from an old bike-flashlight. This HP has only been plugged into the wall once in the last 20 months.. otherwise, when it's running low, it sits on a windowsill. There's plenty of room on that Sill for a Cell Phone, a Voltmeter, a TV remote, Indoor/Outdoor Thermometer and a bunch of other items that still burn through little batteries.

I could do the math against buying AA batts and such, which can actually show a HUGE advantage compared to the cost savings that a Rooftop PV has to mount when going up against the grid, but I think a much more salient issue in this case is the simplicity and independence of these portable devices, which is next to impossible to put a price on. My HP basically NEVER needs an adapter now.. a little dangerous since I have no idea where I left it last year.. but who cares? I can put it in the sunlight anywhere I happen to be, or under a bright lamp if the Sun isn't available.

I do have some bigger PV up on the roof, which feeds isolated systems, like my solar hot air heater, but I really like these little portable items as some of the most interesting applications for Solar PV.

Walkie Talkies - Screwgun Battery Charging - IPhones/Ipods - Lightmeter - Laserpointer - Flashlight - Camcorder - Netbook - Continuity Tester - Guitar Tuner - .....


We put in our first little PV system about 25 years ago and our 3.6kW system a little over 10 years ago. You can read more about it by searching for my key post A Trip to Todd's. We are not grid tied but are on the grid.

Everyone around here has a back-up generator. In fact, I just bought a new little 2kW one which only burns 1/3 gallon per hour to supplant my 8kW one that burns 1 1/2 gallons per hour under load. There are times when the power is out when only a generator hacks it for us.

A note about batteries - I have 48 L-16's and they are getting tired after 10 years even with desulfonators.


48 L-16s is 144 cells, way too many to keep equalized (and watered).
My first big battery bank was 20 Rolls L-16s (60 cells) and keeping them watered and equalized was a bitch. I recommend the big 2 volt cells for large battery banks. My current battery is 12 Hawker 2 volt forklift cells, 2200 amp/hrs each. 230 lbs. per. Much easier to maintain. A Sandia study determined that banks of more than 3 strings never equalize and are more prone to cell failure. I added automatic watering this time, money well spent. Also, the tall 2 volt cells stay cooler.

L-16's are 6 volt so there are three cells/battery = 96 cells total. The system was designed by Real Goods and installed by me. They recommended the number of batteries based upon the need for the system to start and run our 2hp, 220volt well pump.

I don't find checking the batteries a big deal. I do it on the first of the month and it takes about two hours total as my back is bad and I have to take breaks. They are also equalized at that time.

I don't consider this a great amount of time compared to "panel turning." What do I mean? Well, I initially set the racks pointing in the "best" direction for the time of year. But after a while I asked myself why I didn't turn them by hand throughout the day (I didn't install tracking racks because Real Goods said that it wasn't if the tracking would fail but when - remember this was 10 years ago and the situation might have changed). So, I look at the shadow line now and then and give them a tweak. This way I get maximum output throughout the day. In the summer I get useful power from about 9AM to around 7-7:30PM. This is far better than I'd get with a tracking rack.


Let's see: 48 X 3 = ?

Real Goods was a pioneer in the RE business but upon shopping around I realized they were charging retail++. Good stuff at a premium. A buddy had them price a system for him and when he called me, we managed to get him more panels and more batteries, same balance of system stuff for abiut 40% less and the shipping was paid by the vendors. Sorry Real Goods!

A good article on battery systems:


A great article for those who don't know jack about PV systems, a primer:


Todd screw-up big time! Him out bucking up an oak tree and try to sound smart - Try 32 at three each. Cells right, number of batteries zero!

On a more serious note: This was hot crap 10 years ago. At the time mine was the biggest system Real Goods had designed since one in Belize. I still remember the first Trace sine wave inverters that were over a grand for something that could hardly handle 1kW. Yup, things have changed. That's the problem with being an early adaptor. But compared to my first 100watt system (~$1,500 including panels and controller), I wasn't unhappy.


Reading through there are a few points not yet covered. A friend installed a system for his remote cottage four years ago. A twenty minute fast boat ride -- the nearest grid hydro was over a mile away and would require an underwater cable for most of the distance. Not a real brainer if he wanted electricity without running his generator. To this day his wife still doesn't understand that solar is not the same as flipping a switch as in the city with power for everything -- even Stu didn't viscerally understand the trade offs unless he installed a HUGE system. That would be real costly (still less than the cable hook up). I did discuss all this but....

Last summer they had a lightening strike as did several of their neighbours. His was professionally supplied and installed as were the others. How 'professionally' can be argued but his inverter blew and the back up 6000 watt generator also became toast. His inverter came from 3000 miles away and there was a shipping order error so his solar cells did boo all for nearly 9 weeks. His neighbours had more locally manufactured components and were back up and running in a week.

Surprisingly his insurance covered 100% of all replacement costs --- no depreciation for even the nearly 10 year old generator. 'Course his insurance premium has risen by nearly $1,000 for each of the next 6 years.

Sounds like Stu needed a lightning arrestor on his system - I routinely included them in my designs. Cheap insurance.

6. Are there any particular issues with inverters that readers should be aware of?

Inverters convert direct current to alternating current (PVs produce DC, the grid is AC). With inverters, as with most things, you get what you pay for. Inverters produce AC power in different ways. Cheap inverters (like most car inverters that you plug into your lighter or hook to your battery) produce a "stepped" waveform to mimick the true sine wave that grid AC power has. More expensive "true sine wave" inverters produce a waveform that is (nearly) identical to the grid's waveform and frequency. Many electronics, CFLs and anything with a clock that counts cycles don't like the cheaper "modified sine wave" inverters. Premature failure is often the result. Any utility approved grid-tie inverter will be true sine wave. Most of these will also include the electronics and connections for the PV array.

Off-grid inverters are designed to be connected to a battery or bank of batteries. Many also have connections for generator power, grid power (if you have it) and are battery chargers (a battery charger is an inverter working in reverse in this case). A good off-grid inverter will be programable to do a lot of things. They can be set to autostart a generator or charge the batteries from the grid if your batteries get low. They can also control other equipment. The DC voltage of off-grid inverters range from 12 vdc to 48vdc (with a few exceptions). These inverters come in 120 and 240 vac versions 50 or 60 Hz. They can also be stacked and combined for more power:

One thing to remember about battery connected inverters is that they can pull a lot of amps. An inverter producing 1200 watts from a 12vdc battery is using 100+ amps(amps X volts = watts), so you need big wires. Proper fusing and wire size is critical. Many fires have been started by folks that didn't understand this. I use 4/0 welder wire for my battery cables. Always use copper! Keep your battery cables short! Your inverter should come with cable specs or your supplier can sell you the right ones.

A good inverter is more than 90% efficient at converting DC to AC.

A third category of inverter is sort of a hybrid of the off-grid and grid-tied inverters, called grid-interactive.


They can allow you to be off-grid and sell only your extra power to the grid. They can also be programmed to top your batteries off from the grid during off peak periods, and other neat things. You can store power when it's cheap and use it during expensive peak times. Not sure of the EROI of this, though.

Run clocks and smoke detectors from rechargeable batteries and use mechanical windup alarm clocks so the load on the main batteries can be zero when you go to bed at night. Minimize the discharge of your batteries to extend their life.

Coincidentally the Feb/Mar issue of Home Power Magazine has a pretty decent article on how inverters work.

We have 9 KW of PV solar (Kyocera panels), plus a solar water heating system that I bought as a kit and installed myself for about $3K. The system is grid-tied with 12 KWH of battery back-up. It produces about 13,000 KWH per year, about equal to what we use; the house is all-electric. I am happy with it. Still thinking of adding another 3 KW for charging electric vehicles; I currently commute to work using an electric bike and regular road bike.

An electrician installed an "emergency subpanel" that is connected to the solar inverter (Xantrex 6048). This subpanel covers the house lights and outlets, refrigerator, microwave, a few kitchen outlets. If the grid fails, the battery backup powers the subpanel. Not covered are the electric stove, air conditioner, dryer, electric backup for the water heater.

I have an EE degree and a computer science PhD, but by the time all the above stuff was included, it really was rocket science, and I'm glad that Texas Solar Power installed it.

We recently had an outage of the whole neighborhood lasting about 45 minutes. Switch-over to the backup system was completely seamless: the only reason we knew about the outage was that my wife asked why the clock on the stove was not working; then I went outside, and the whole neighborhood was dark except for our house.

A lengthy grid outage is a real possibility. There is about a 2% chance each year of a large solar flare and electromagnetic pulse that would likely take out the grids in the northeast 1/3 of the US plus the Pacific northwest. It could destroy the large power transformers, which could take years to replace. Without electricity, of course, you lose gasoline pumps and lose water after a few hours, and without water you can only live a few days.

Is it worth the cost? I think so. Does anyone reading this site think that electric power will stay cheap? Austin Energy has a great local rebate program, plus there is a 30% Federal tax credit. With those, our system has a payback time of around 12 years at current electric prices (about 10 cents per KWH). Look at that another way: I have a safe bond that pays 8%, tax free, inflation adjusted, and
hedges my energy cost for the rest of my life. Wall Street types would kill for such an investment.

How is your PV system protected from the EMP?

The EMP would produce DC currents in high-voltage power lines, which would move the large power transformers into magnetic saturation, causing heating and burnout of the transformers, which are designed for AC but not for any DC component.

How is my PV system protected? We won't know for sure until it is tested, but here is what I think:

  1. The PV system has lots of aluminum conductors, as supports and module frames, that are grounded, and conductors are short, hence much less induced current than in long high-voltage lines far above ground level.
  2. The system already includes lighning arrestors, which are needed since it is on the roof and possibly subject to lighning.
  3. The system is already designed to handle DC currents; that's its job :-)


Where did you get the two per percent annual probability grid wrecker solar flare figure?
Do you know of other estimates ?

If the enginerring profession and tptb who deal with emergency management(every body from homeland security to the local electrical coop) take this figure seriously it is obvious that a lot of emergency preparedness money is being misspent otherwise and that there should be an emergency stock of transformers and switching equipment built up.

I know that this would be extremely expensive and take a long time to accomplish.

The two percent probability is a rough estimate, based on the fact that it has occurred 3 times in the last 150 years.

The following NASA link shows a map of the "area of probable power system collapse":


The most recent event, in 1989, burned out a power transformer and took down most of Quebec:


An event larger than 1989 occurred in 1921. The largest was the Carrington Event of 1859:


This event induced currents in telegraph lines that shocked telegraph operators and started fires in telegraph offices.

The larger power transformers are not even made in the US any more. Lead time if you order one today is 2-3 years.

There is a fix, by adding special resistors to the power systems to discharge the DC currents to ground. Around $100K each. I think some power systems may be installing them, but it takes time.

Reducing your electrical consumption down to where you can afford the PV is the answer.

Most folks do not/ will not do that and will remain on the grid

Currently most PV systems are for those who make enough money that they can use a tax write off , or folks who are to far out to get the grid.

An example .....
Simple Solar Homesteading


Most folks do not/ will not do that and will remain on the grid

Currently most PV systems are for those who make enough money that they can use a tax write off , or folks who are to far out to get the grid.

Around here I think the average system size is pretty large. So I think there are a lot of very rich people, who are buying PV to cut the cost of their overpowered toys. But, for folks on ordinary budgets you are right. I've seen six installations in my immediate area. Only one is my modest size (14 panels), several look to be at least twice as large. So I think it is mainly rich power hogs trying to avoid the high tarrifs that kick in for people that use ridiculous amounts of power.

I've heard that Solano country vineyards have had hundreds of ground mounted panels stolen. In my case on a residential roof, State farm didn't batt an eye -or raise rates to add my system onto the homeowners policy. But if you are in a remote area, that theives might think makes a good target, it might be an issue. The contractor, was in a big hurry to move the panels off his truck into the back yard, as he didn't want someone driving off with them. (And I live in a pretty safe neighborhood).

We decided to see what you could do at the frugal end of the spectrum, and have now been off the grid for five years.
Total set-up cost NZ $3,200 (perhaps $2,000 US). One (yes one) 50 watt panel powers the house, only needs a kick in the pants if we get 4 or more sequential cloudy winter days. It peaks at 3 amps, and we track the sun (tilt, rotate, and seasonal inclination)- much more efficient. House is 12 volt, all lighting homebuilt LED'S plus the odd Cree. Batteries are ex computer-backups (4 x 65 amp/hr, sealed lead/acid) still going strong. They chuck them out after 18 months, and they've spent their whole existence fully charged. You get them for scrap value.

The trick is if you don't have an appliance, it doesn't use power!

Washing machine and vacuum cleaner are 240v ac, for which we fire up the 'genny', and charge up everything in sight at the same time. Petrol costs average $1 NZ / day. I'm working on a 12 volt drive for the w/m..., and a pelton-wheel in the creek driving a GE washing-machine motor (reconfigured star-to-delta) will replace the 'genny' soon. Fridge is 12 volt and top-loading, the body of it is outside the shady (our South) wall of the house, but accessable from within.

The house draws, full noise, about what our inverter does idling (which is why we don't invert). 1.5 amps......(wait for the yowls from the disbelievers!) The only thing that overtops that is cranking up the stereo Real loud.....so we tend to do that on sunny days. Thick cable is the antidote to running a low voltage.

Compared to the $30,000 to get grid-power to our site, we were ahead from the word 'go', and anything under 50 volts doesn't need a permit, or a 'sparky' to install it, hereabouts.

My first PV panel, bought for a boat in 1980, still put out the 7 watts it did back then, nowadays powering an electric fence. They last if not physically abused, although some (early BP panels in my experience) tend to drop in output a bit over time.

You do, though, as somebody above pointed out, need a partner on the same wavelength.

From a UK perspective solar is beginning to be interesting. I'm about to contract for a 1.67kw grid-tied system that should generate about 1500 kwh pa. Until end of March system attracts a grant of £2500 and govt are introducing feed in tariffs in April of 36.5p per kwh generated plus 5p per kwh exported. With roughly 60% of generated electricity replacing part of my annual use of 4500kwh the total annual return of £667 on net capital cost is 11.24%.

We built in Lorraine (North East of France) a low energy house with a lot of technologies including solar PV panels.
We are living in since mid 2008 and for the year 2009 we have all measurements.
32 m2 of panels have produced 4 074 kWh. The max in summer was 28 kWh per day, in winter 10 kWh per day. Panels are Kyocera and inverters are Fronius (Austrian manufacturer). The house itself and the PV systems were installed by a German company (Weberhaus.de). Cost for all PV material and installation was 30 k€ and we had 7k€ from the government as incentive. The estimated pay back time for energy return is around 3 years and for cost it is around 17/20 years because here the kWh is paid 3 times more than the grid tariff, 0.33€ kWh instead of 0.11. To better understand the day to day production, I installed outside temperature sensor, panel temperature sensor as well as insolence sensor. I have a data card storing measurements every 20 min, it is very interesting for me to have real data as I’m giving lectures about this overall project.
For our global energy consumption in 2009 we are at: 16.7 kWh /m2/y all energies (wood, gas, electricity produced and used for all purpose). The house is 196 m2 (2 110 sq ft) with a Prius 2010 in the garage (waiting for the plug in version…). For the carbon foot print we are very low (1 kg /m2/y) thanks to a green electricity contract (hydraulic along the river Moselle) with a local provider.
For people interested I can send the pdf one page summary of the project, so let me know.
The web site of the International Energy Agency dedicated to PV is very interesting for worldwide informations and documents.


(tried 6 different ways from Sunday to get the photo to post, and can't....so go to the link if you want to see my setup )

We put in a 2kw system on 2 active trackers I built ( about $600 in each mount )last December, then added another 1kw in May. It generates about 250-300kw/hrs/month. Grid tied with battery backup. All self installed, about $20k in the system. Battery is a 1200amp/hr AGM unit surplus from a cell phone company ( cost-$100....seriously )

SolarWorld panels, Outback everything else.

I did it since I believe long term, the grid won't be around, and this will give us enough capacity to run refrigeration and lights.

We are on TVA electric system, and they have a good infeed tariff ( 0.21/kwhr ) for all you produce on solar ( 10yr contract ) + $1000cash payment on completion of install....combined with the 30% Fed credit, I figure we have about 13k out of pocket....and last month's electric bill was 20 bucks. Still a long payoff, moneywise, but peace of mind is worth a lot.

Power was out for 3 days just before Christmas (heavy, wet snow ), but not for us....manual transfer switch in the garage, and most of the house runs just fine !


I put your picture up. Thanks for your effort! It is not easy.

The concern I would have with this arrangement is that it looks like it would be awfully easy for someone to steal the solar PV. When I was out visiting BP's Wamsutter natural gas facility, it had ground level solar panels (mounted fairly vertically to get the snow to slide off). They said that theft was a problem, since there were very few workers driving around the area. If grid electricity gets to be an issue, I would think theft would be even more of a problem.

Theft might well be a problem, but I bet they once said the same thing about owning cars and other valuables that we have nowadays. Computers and TVs..

Car theft IS a problem, but there are also societal constructs that deal with it.

The first thing that will likely happen if Society breaks down is that many or most people will work pretty hard to reestablish it, the likelihood of which is of course subject to the level of doomerism one has decided upon.

Not that this becomes a non-issue (theft of PV).. but it's not a death-knell for this techn, either. Higher poles, Alarms, various disincentives would be applied to see what improved the odds. Anti-social behavior will be a factor in any case.

Thanks for the photo help, Gail.

As to theft, in some cases, I can see that might be a problem....however, here:

1. They probably won't steal what they can't see.....the house and solar are not even visible from a public road...we live back on 75ac. The road is a small lane that ends at our gate.

2. The would have to get past a locked gate at the end of the public road, a system of sensors by Dakota Alert ( magnetic in the drive plus motion sensors) that sound off nicely in the house, two large free roaming dogs, AND the "Glock/Colt/Bushmaster" home protection package.

3. I work at home, and am here much of the time, or my away time is very random.

4. All of my neighbors are equally zealous, in 30 years here, I don't recall a theft problem. Once, someone stole a work vehicle full of tools in town, and parked it out here to hide it temporarily. When they returned to pick it up, several of us neighbors met them, and suggested he and his cohorts might want to "sit over there on that log" until the county sheriff deputy arrived to insure their future well being, and recover the property. It's THAT kinda place....very little foolishness is tolerated....ahahahaaaa

I've used a small PV panel while camping, and the little LED indicator lights it has have made me aware of how the orientation of the panel to the sun really seems to make a difference on the power output of the panel. Now I'm thinking about some panels for the house, I'd be interested in anyone's opinions on sun tracking mounts - they have been mentioned in passing in a couple of posts, so if anyone can expand upon their experiences I'd appreciate it.
Cheers, Phil

W have four arrays on active trackers and the trackers have increased our PV output 20% - 40%, depending on the season. One of the trackers is a $1300 Wattsun, very nice, but we have replaced the electronics twice. The other trackers I home built for less than $300 ea. from old heavy-duty satellite dish mounts (still plentiful and usually free). The actuators on these old mounts are 24vdc and run off of our DC bus. New heavy-duty actuators are less than $150 if the old ones need replacing. All of our trackers are single axis (east to west) so I adjust elevation for season (easy). I like the mounts from the old Curtis Mathis 10 -12 foot dishes, really heavy duty. I build the racks for the panels from uni-strut available at Lowes or Home Depot.

I use tracking controllers from a guy in BC: www.theanalogguy.com . I've had a couple of the sensors go bad but he made them good, and they are cheap, so I keep spares. The first tracker I built had a simple timer that set the array at three positions, morning, noon, and afternoon. Even moving the array this way increased output significantly.

There is an ongoing debate as to whether it is more cost effective to add more panels or to track. My homebuilt trackers had a better payback, but do require some maintenance.


Your tracker building experiences and results pretty much are mine. I looked at a tracker built on an old C band sat mount, then built a little beefier one in my shop. Mine is single axis....I figure I have about 600 bucks in each, including the concrete in the bases. I can't buy one panel for that price, so I'm happy with the extra output.

I also use the Analogguy's controller....I tried RedRock, it was a piece of junk, ( and DON'T even bother trying to get any tech support out of him ) and another one ( can't recall the brand ), but Analogguy's has been the most "plug and play" version to work....and he is very helpful if you have questions/problems.

Even with his, I had a problem with the board burning out if the limit switches on the actuator sticks, so now I run them thru a set of relays so the board is only connected to the relay, and the relay then connects the actuator to the power supply. THAT stopped any further problems, so you might want to consider that route. Also, by doing this, I can use one controller to run as many actuators ( 2 in my case ) as the limit on the relay will allow.

Well Andy, we're just like two peas in a pod. We even have the same driveway alarm (ALERT ZONE ONE! ALERT ZONE ONE!) Great minds think alike, huh?

I tried to get two arrays on one tracking control but they got out of sync. I put 5 amp fuses on my actuators in case of limit switch failure. Have you had any trouble with sensor failure? I had to replace one yesterday (just $15, but...). I replace one about every year. Not sure why they fail.

What part of TN you in? We're about 35 mi. from the TN/NC line.


We're about the same from the TN/NC line.

I guess this forum has no PM type feature, so send me an email at fa_que@mail.com ( ahahaa.....throwaway email I don't care about ) and I'll send you my real email.

Emergency conversion of a grid-tied inverter in a power outage?

Hypothetically, if the grid went down for a few days and you wanted the re-enable your grid-tied inverter to power your house somehow, is there any easy way to do it safely?

If you had a generator running and supplied 240ac to the inverter, would it start generating AC again?

I realize the dangers of power flowing back to the grid (which I would disable), but I'm just wondering if there was some easy/cheap way to re-enable the PV array in an emergency at least to run the freezer/fridge for a while, etc.

There are a couple ways.. (not necessarily to code, but can be done safely)

One is to tap off of the Array 'before' the inverter, and send that DC current to an independant charge controller and batteries. You HAVE to know the peak voltage that string of PV panels is capable of generating to be sure your charging equipment is safe, and YOU are safe. This would really require having a shutoff that separates the PV from the Grid Inverter as well. I don't know if there is usually a contactor or a breaker between the Array and the Inverter in Grid-Only setups..

The other is to get one of the grid/off-grid capable inverters, ( http://www.altestore.com/store/Inverters/Grid-Tie-Off-Grid-Capable-Inver... ) like these ones.. then you can invest in as much battery capacity as you deem necessary/affordable.

I wouldn't suggest messing with the grid-only inverter's shutdown mode. I think that would invite both a tenuous supply and a chance to damage that inverter. It might be more reasonable to just be ready to work on the DC side, and maybe have a little backup inverter for those situations.. it could be the kind of 200-600 watt deal that you use in the car, which is a very useful item to have anyhow.


I don't know if there is usually a contactor or a breaker between the Array and the Inverter in Grid-Only setups.

There is. And on the AC side of the inverter as well. Aside from safety, this makes it a lot easier to repair or replace the inverter if necessary.

Written by sharppa:
If you had a generator running and supplied 240ac to the inverter, would it start generating AC again?

A grid-tied inverted is designed to shut down if the voltage from the grid is too high or too low and if the frequency to out of range. A generator used in place of the grid power would have to operate within the appropriate voltage and frequency range to activate a grid-tied inverter. When my generator runs without a load, its output voltage is high. Under a heavy load, the voltage decreases. The ~60 Hz frequency output by my generator is not particularly stable. Also the waveform is not a smooth sine wave because it contains voltage spikes. Although I have never tried it, I doubt that a grid-tied inverter could synchronize to the output of my generator. My guess is no.

My family installed a 10K system of PV panels on poles about 3 years ago, and a roof based solar hot water system last year. The former cost $80K, half of which was paid for by federal and NY state programs and tax incentives, and required us to use an certified installer. The latter cost $12K.

Our PV system is grid-tied and has a battery backup. We have two separate electircal panels, one with critical systems tied to solar, and another which just loses power when the grid is down. That allows our house to function longer on batteries. We've never tried going strictly solar for any length of time to see how long the system will last that way. Our installers told us about a week, but I think that was optimistic.

We live in Ithaca, where solarization is very high. There are 5 households with solar PV systems in our neighborhood.

Although we had the money to buy a system, we have had little time to understand it. We can see the difference in our electric bills, and we believe it to be about $150/month on average for the PV -- although the price changes in electric make it difficult to be sure.

The hot water system works amazingly well, for about 8 months of the year. You can see 160 degree water coming in on sunny days on sunny days in November.

We had a significant problem with power fluctuation that would shut down our computers. Our business is in our home, so this was a big deal. It took more than 8 months of haranguing our installer to deal with the problem, and they are personal friends. The problem here in Ithaca is that the demand is so high that the 4 companies that work on it don't return calls for months. Traditional electricians won't even look at the system.

The only other problem we've had is with a super low energy washer we bought recently. It will not do its ultra fast spin when the sun is shining. The chip inside it (or whatever) is so sensitive that our system doesn't provide smooth enough power. The washer stops itself mid-cycle. We've had the installer out and asked for help from PV folks, but have had no luck resolving the problem. We wash our laundry at night and early in the morning -- which sort of defeats the purpose of solar.

Overall I'm very glad we installed our systems, for the added security we have. They take almost no maintenance, except for scraping snow off of panels. For people like us, who have little technical knowledge and little time to learn about the system, it is unfortunately hard to quantify the benefits. I have an Outback "thingy" that is supposed to connect to a computer and report results, but it has sat on the wall in the basement for two years providing information to nothing. We are unable to find anyone with the expertise to hook it up. Hopefully, as the industry progresses these kinds of things will become more routine.

When I retire, or when the SHTF, maybe I'll learn more about my system and be able to troubleshoot it myself.

Your Outback "thingy", or Mate has a simple RS-232 serial connector (unless they changed it to USB). Many new computers don't have this serial port anymore, but you can get a converter (USB to RS-232). I monitor my Outback and Trace stuff using software from righthandengineering in WA. http://www.righthandeng.com/

See the picture I posted above. Setup was simple and anyone with a computer background should be able to do it. Its about as hard as installing a modem.

There must be something wrong with your system if you are having problems with voltage or freq. fluctuations. My Outback inverters produce very clean and stable power, even with variations of 6-7 volts on the DC bus. Never had this problem. I would check for other equipment causing this, such as a refrig. compressor having a hard time starting or a fan motor with a failing capacitor. Make sure your DC connections to the inverter are ok. Grounding can be a problem as well.

A UPS designed for computers should solve the voltage issue.


I'll post the 'hey go buy one panel' solution.


This little device is an AC inverter for one panel. The projected price was to be under $200 a pop.

Seems a company called enphase has 'em also.


So one can buy just 1 panel and 1 grid tie inverter and be in business.

(oh and ask your FedGov to add solar panels to the 179 deduction for business)

Can the micro inverter be plugged in to an AC socket ?

With an adapter cable, yes, but there's no good reason to do so, and it'd be illegal.
EDIT: Upon reflection, Enphase require a 240V connection to the grid, so you couldn't plug it into a 110V socket. I don't know about the other brand.

but there's no good reason to do so,

As the links are grid tie inverters they need the grid to sync to so that they will actually output power.

Unless they have an advanced unit that can operate with and without the grid sync.

Shhhh, you are not supposed to. But yea. It was part of the saleman's sthick back where execltech was pimp'n their little inverter.

Because you'd be violating various laws about inspecting wiring connected to the electrical grid.

So you walk outside and shut off your main disconnect at your meter.

If you don't have a disconnect (in the USA, almost every 200A or lesser service won't have one), just pull the meter out of the socket *warning, don't screw up, and cover the hole so kids can't touch the live lugs if the grid power comes back on*).

At least in the US, the meter just pulls right out. Quite often you'll see some little plastic tabs lying in the bottom of your meter box from the last time your power was shut off. They slide over the lugs on the back of the meter (covering the metal contacts), and then you can put it back in. Exact same method the power company uses for disconnects.

You've now violated a power company rule about pulling your own meter, but likely not any actual laws, and are now completely disconnected from the grid. Good enough to get you through an outage. Incidentally, most of the no-tamper seals on the meter box can be opened with a bit of patience and something lockpick-like. Tiny screwdriver works. Or you can just cut it off, and just hang it back. Probably nobody will notice for years, as long as you don't take advantage of the opportunity to start stealing grid power. (they do notice that quickly, and can generally track it to the exact pole/transformer and check the few houses connected to it)

I question the "200 amp service and smaller does not have a disconnect".

It has been a decade since I read the code, but I believe that disconnecting means are required (and have been for decades).

Usually it is a large breaker at the top of the box. Turn that off and you are off grid.

An older solution (no longer kosher for the main box under the meter) is to side wire a breaker (usually top left pair from memory) with the feed from the meter and this breaker feeds the rest of the house. Throw that breaker and you are disconnected from the grid (supposed to be labeled "Main Breaker").

You are likely to find the side wired solution on a breaker box installed in the 1960s or so.


Those would be perfect for me except for the fact that I live in the only country in the world that has a 110V 50Hz supply. This means that US spec grid tie/grid interactive inverters won't work and neither will European spec. I have managed to find a couple of non UL listed micro-inverters on ebay that just plug into a wall socket. This is where the problem lies as it relates to UL certification.

Under certain conditions a number of these could be plugged into the same electrical circuit in such a way as to overload a part of the wiring of the circuit but not trip the circuit breaker. This presents a fire hazard so these really should have a circuit of their own that is not shared by appliances. The fact that they can be plugged into any old wall socket means their safe operation cannot be guaranteed. One of the manufacturers of the units I have is seeking to correct this by providing a unit with fixed wiring specifically for the US market.

I'm having other issues with the inverters I bought as it relates to power output and reliability. Both types are not producing as much as I think they should and one type doesn't always start in the mornings and frequently shuts down during the day (It might be something to do with shading by clouds). One of the manufacturers has committed to solving the power output issues and the supplier of the other type has pointed out they now have a Gen II unit that they might be willing to exchange for the ones I bought

If you just want to buy a system and start producing power ASAP my way is definitely not the way to go. If you want to learn from experience, it's one way (sort of expensive).

Alan from the islands

Before answering any of the questions, it's important to make the most cost effective energy investments first; energy efficiency and conservation. Reducing energy use means far less PV equipment will be needed. Our house uses about 1/4 of the energy of our neighbors, so our PV system costs are consequently 1/4th of that our neighbors would need to install.
Here's a good DVD to help you cut your energy use - Kilowatt Ours

Energy efficiency means that one device will use less energy than a similar one, or energy demand is reduced through other equipment means, such as insulation, weatherstripping, etc. Look at all the old appliances and consider replacing them, especially the refrigerator and the heat pump (or AC), if the home has the latter. Compact fluorescent light bulbs should be installed in the lights that are used frequently (except those that are turned on and off many times in a day).

Conservation means using energy wisely. We don't leave unnecessary lights on, always wait to run the dishwasher 'til it's full, set the thermostat at modest comfort levels, etc. See the DVD for more...

I had a 2kW PV system installed 10 years ago; I bought the equipment through a buy-down promotion for much less than normal, and hired a PV installer to install it.

I don't suggest anyone do it themselves, unless they have very good electrical skills and can properly interpret the codebook in force in their area. Too easy to make a costly or deadly mistake...

1. Is it best to work with someone who both sells and installs solar PV panels? Or is this something that people end up doing themselves, using a variety of vendors?

I would suggest going with one company, and getting one all encompassing quote from them. Only go with certified PV installers.

2. What brands/ types are best?

Major brands with a proven track record, as someone above mentioned.

3. How much maintenance is required?

Next to nothing for the panels/inverter. Batteries are variable, depending on whether they are flooded lead-acid (the most maintenance), gell or AGM (much less), etc.

4. What experiences have people had who purchased solar PV, then moved to another home? Did the addition of solar PV help the resale value?

Not moved yet, though have seen more interest in (and higher valuation of) green homes in this area.

5. What have buyers experience with battery back-up been? Is a small amount worthwhile, even if a homeowner is on the grid?

Depends on a number of factors, such as cloudiness likelihood, amount of power needed during emergencies (i.e., critical loads only), etc.

We have 12 kWhr of battery backup, and it has come in handy after a hurricane passed nearby, knocking out power for 3 days. The first day was cloudy, then the next two were mostly sunny, so we made out quite well (most homes with generators were out of gas by sometime during the second day).

6. Are there any particular issues with inverters that readers should be aware of?

Having had both Trace and Outback, I prefer Outback. Pairing up the inverter and charge controller from the same manufacturer will reduce the number of potential headaches.

7. If you have purchased solar PV, are you generally happy with it?

Very much so. It has encouraged me to 'live within my generation means', as I am net-metering.

8. Where does one find good material to read regarding solar PV?

Home Power Magazine. Purchase the last 12 months of back issues, or buy an online subscription.

I address some of this in my bio. My stand-alone off-grid "system" in California was two PV panels moving to a third one. We lived there for 29 years. I saw what an inverter will bring--AC appliances, electronics, etc.--but never bothered with it.

We were in the woods so inter-tie was out of my reach. Nearby a neighbor had a 24 panel array and he could operate a power tool and washing machine at the same time. I believe his four kids were barely aware they were off the electric grid. In contrast my daughter was embarassed by our puny PVs, but now at 26 she's working full-time in the bicycle biz.

Batteries weren't back-up for us. They were integral, but they were ordinary l2volt car batteries. I had a gasoline generator for charging them and pumping water, and another gasoline pump. We were TOTALLY dependent on gasoline.

I bought the first two panels in the early 80s for a pittance and the third on sale for very little. The batteries lasted for decades, but as you can see, we were low-load, just lights, radio and a tape deck.

Now I'm happy to leave all that behind. My house is all-electric, and when the grid goes down, if we don't have outdoor cooking under shelter in my yard in this Hawaii town, we'll be crying. But if we do, maybe we and others will be stripping this island like the Haitian side of Santo Domingo.

Eventually I bought a tracker, to answer a question above. It was manual, on a big steel post set in concrete, and it was great to go out there and turn the PV panels once a day or so, and to change the angle to the sun seasonally.

And about resale value. I believe the young couple who bought my property were ecstatic to find a place that was secluded but only 25 minutes drive from town, but they had a bit of money and probably re-built my puny system, or built a new house.

Generator power is $.50 to $1.00 per Kwh.

Some of the inverter generators may be able to
do a bit better, but a 3600 RPM Generator is
very expensive to operate for extended periods.
PV is has great payback to replace Generator power.

You can economically only charge batteries part way with a generator,
since the last 20% charging is best to charge at constant
voltage and let the current fall off. PV is perfect for

It costs $.10 to $.20 to store electricity in a Lead
Acid Battery --- Total Lifecycle costs. More than the
costs of Grid Power. Too bad Edison Cells
( Nickel Iron ) are not made in USA anymore. They will
last decades.

Just curious. sunelec.com seemes to be catering to the off-grid/export markets as their heavily discounted panels are often not UL listed. I bought some Evergreen blems from them. I know they're Evergreens because the terminal block that the two leads come out from on the back of the panel says so. Why would they not be UL listed? I suspect that Evergreen couldn't be bothered to go through the time consuming (and expensive?) process of UL certification for what are in effect seconds so, they rather just sell them as such. Not that they are any less safe than the A grade stuff. Am I way off base here?

How much business do US based members (FMagyar?) do with these guys? What's their reputation like? Every time I have had to do business with them they seem extremely busy but, they've delivered both my orders within days of cashing my checks.

Alan from the islands

You don't need to buy a tracker. Seasonal adjustment can be by 2-3 tilt positions (we just use a bolt through 3 optional holes - every 2 months if I remember. Then tracking becomes (particularly in winter and if you're the wrong side of the 45th parallel) a simple 8-hour arc.

We use an old heavy-duty clockwork mechanism, driving a pinch-roller on a piece of 1/4-inch rope!

Just set it up so it tracks the arc you want in the time you have sunshine. Just a matter of the size of the pinch-roller.

Why waste your scarce energy driving something? Although I guess you can trace the energy we use winding the clockwork key, to some farmer's tractor via our food.......

I read somewhere that the most economical way to do PV (assuming you are starting from scratch) was to buy 12V DC RV appliances and buy panels per appliance minimizing the equipment between the panels and the appliances. In other words, if you start with 12VDC and your end need is 12VDC, there is no need for inverters or any of the other electronic equipment.

Is this approach realistic? What do 12V DC appliances do when the voltage drops too low? Wouldn't that damage them?

We want to have some sort of primitive shelter off the grid and I am trying to figure out the cheapest / easiest way to retain some modern amenities.

Most panels nowadays are not 12V, and not designed to work with 12V, so unless you limit yourself to 12V modules you'll need a minimum of some electronics (transformer, charge controller) to charge 12V batteries or use 12V appliances. You'll also probably need some kind of charge controller even if your panel is 12V.

IOW, you can probably eliminate the inverters this way, but there's still other things you need. If by "modern amenities" you mean lights and a stereo, this approach could be more economical. If you mean a washing machine, not so likely.

14V nominal panels are designed for 12V systems (as are 28V for 24V systems) because it is assumed that you are going to be charging batteries. Traditional lead/acid batteries have a charging voltage of 13.8 V so a 14V nominal panel is designed to provide enough voltage to provide that after going through the charge controller electronics.

I really can't imagine an inverter-less PV system without batteries. You will only have power when the sun is shinning. Even a passing cloud could shut you down and it'd be totally useless at nights. Inverters just allow you to run off the shelf appliances, as opposed to 12V RV appliances, off your batteries/PV and are probably not the most expensive item on the shopping list, provided your appliances are not HVAC, electric stoves, clothes dryers, water heaters etc. (heat or cold producing appliances use relatively huge amounts of power compared to radios, tvs, fans and even most modern light bulbs).

Alan from the islands

I have 4 x 175W panels (in the UK). Two are horizontal, as significant power can be picked up from a cloudy sky if the panel "sees" the whole arc, and two near vertical facing due south. The latter pair provide some power on bright mid-winter days. The system feeds 50V into a 600AH bank of ex-telecom batteries, which drive a 3 kVA UPS used as a 240V inverter. The 240V is used to power fridge and freezer, whose demand matches the sun's power reasonably well, and in emergencies, the oil-fired central heating. The panel arrangement is not optimal for maximum power delivered over a year, but the output is more consistent (I hope).

24V is generated by an auxiliary DC:DC converter, and powers the solar hot water pump circulation pump, this computer, and some LED lights.

Performance: I get about 70% of "nameplate" rating during the summer, and have seen 40% during midwinter, the latter only in the half-hour around noon, however.

The system is not grid-tied.

As an ex-electronics engineer, I don't quite understand the comment upthread about the inverters wearing out, they shouldn't. Their failure rate may be increased by bad line conditioning (lightning, magnetic storms, switching transients) but there are no moving parts (except maybe a fan) so they shouldn't "wear out". My UPS is secondhand, 15 years old and still going fine.

A good website for solar insolation in Europe:


Big inverters, especially older off-grid ones, have relays and fans that can go bad. My older Trace 4024s each have 2 60 amp relays (built-in transfer switch), 2 fans, and smaller aux relays for gen. start, etc. If these inverters aren't cleaned periodically they can develop heat problems. One post above regarding a Honda generator being more reliable/repairable than a system with inverters has me confused a little since most Honda generators have inverters these days. My inverters have been running for years without problems (touch wood!). A friend has an old Heart Interface inverter he scrounged from a wrecked ambulance in 1984 (he claims) that has been running continuously since then. It looks older than dirt, but still works fine.

We have 1.2 kilowatts of pole mounted panels at our home in southern Ontario. We are currently having a 10 kilowatt project installed for us on another piece of property we own nearby. Under the recently enacted Green Power Act here in Ontario, homeowners with solar generation capability (up to 10 kilowatts) can enter into a 20-year contract with the utility to sell power to the grid at just over $0.80 per kilowatt hour. The ROI is in the vicinity of 15% per year.

Ontario residents with a Registered Retirement Savings plan (our Canadian equivalent of a 401K plan in the US) can take advantage of some other regulations to enhance the benefits even further. Details in my blog at http://www.juniperrock.ca/wp/?p=57

After several years of lurking this site, I've been drawn in by the home PV issue! Here goes.

We live in southern Maine, one of the worst places in USA for solar. My family has been off the grid since 1983. In the first ten years we went from candles, to Aladdin lamps, to one panel/one battery/and one tail light bulb mounted in a tuna fish can! We kept adding panels and replacing batteries over the years. We are now running with a 1.35KW Kyocera array, 12 L16 batteries, an Outback controller and inverter (sine wave). So, we've come up in convenience, not down. We have an E2000 Honda generator for these darn long, cloudy winters. We have over 2000 square feet. Unlike Bill McKibben's kids, mine have not yet started calling me the Dark Lord, but it's because they think of other rude things to say - and I ignore them as long as they are saying it in the dark ;-) The sun provides insolation, the son provides insolence.

We heat water and cook with propane. We heat the house with wood and some sun.

I like to tell people that once they have gotten their monthly power bill under $20 they are ready for solar. Most of us can barely afford small systems, much less 3KW and up systems. Yet, coming from candles, we feel we are living better than kings of 200 years ago. Indeed, with CFLs, LEDs, efficient washing machine and fridge, we are living better than kings did. Life is good.

I have put the whole thing together myself, although I expect my electrical engineering background made that more possible for me. If you do this, read a ton and visit some sites. There's plenty of information available if you are so inclined.

Batteries stink. There's no way around this. You will likely kill your first set of batteries and then you will keep they next set charged and watered. Someday someone will invent something better and less expensive.

If you can get a pure sine wave inverter, do so. The modified sine wave ones work but cause all sorts of noise in audio, video and telephone equipment. It's now worth the price difference.

I like living with solar. I think my kids (now one in college) get sick of me telling them to turn off the computer by midnight, but it's given them some tiny sense of power and energy. A bicycle generator would have done wonders... My wife is fine with it. She gets it. It was really her idea to begin with, so many years ago.

Maintenance: water the batteries and keep them charged. Watch your power income (sun's up, and no power? must be a line of snow across the entire array!). Change the oil in the generator. My first Honda lasted me well over 15,000 hours and 12 years. I expect the E2000 to do the same or better.

Best wishes to anyone doing this, but don't do it to save money! Like others have said, this is not fast ROI. I could have bought a lot more electricity than I have made with PV with the money I've put into all the gear. But, even if I had power running up to my front porch, I think I do it all over again because it enforces an awareness that few have and that I enjoy having.

I live in Tucson where there is plenty of sunshine. I will have a 12.4 kw system completed by month end. I selected the installer who did my pool heater. He is an MS in EE with 25 years of appropriate experience. There are many start ups out there who are in it for the thrill of having a green job and I fear that their inexperience will kill them or some customer! My system will cost about $74k and after rebates from Tucson electric Power and tax savings will cost about $24k. I am using all German conponents - Solon 280W panels made in Tucson and German inverters -2. I conservatively expect to generate 23,000 kwhr per year and have about a 10% ROI in year one. Tucson Elecric rate is about 10.3 cents a KWhr, is coal based, and likely to see major increases in the years ahead. The panels will last 30 years and are high quality frames - the Germans make good stuff -and the inverters 15 years. Inverter technology is expected to get better and cheaper so that I would expect to replace them for less than I am paying today. I sought advice from industry insiders and was encouraged to buy German, Japanese, or American product. My installer has never had a failure from Solon or Sharp (largest in world). Chinese panels and thin film panels have not demonstrated equivalent reliabilty. But they will get better. Rebate rates are and will continue to go down as hardware and installation costs decline. Now is as good a time as any to purchase the equivalent of an inflation protected bond. I would not consider batteries unless I was off the grid or utility reliability was failing. Cost and product life without the subsidy would not be interesting. Of course the PV investment without the subsidy would also be a joke.
I would like to see the PV companies design a panel that could be repackaged/recycled in 30 years. Another innovation to think about are security fasteners as theft will continue to increase in the years ahead.

Another innovation to think about are security fasteners as theft will continue to increase in the years ahead.

At a solar convention I went to this summer, a company was there that sold custom fasterners: only you have the screwdriver bit that will turn them. (The company otherwise had nothing to do with solar.) Probably will thwart less sophisticated thieves, but if they have a dewalt 18V reciprocating saw...

Just a general question in response to all the folks who have pointed out how much cheaper it is to run off a small gas/diesel/propane genset compared to solar PV. Isn't this a very BAU way of looking at things? If/when TSHTF I can imagine a certain credit card company running an add something like this.

"Grid connected power $0.56 per kWh.
A backup generator to keep you running when the grid goes down $1500.
fuel for the generator $11.27 per gallon.
A new set of energy efficient appliances and lights $2000.
[pause for dramatic effect}
A off grid PV system for when oil goes over $500 a barrel ...... priceless."

In my case I'm fortunate to have some funds with which to experiment with PV and one of my worries is that I may spend $X now only to find some time in the future that, I could have spent some fraction of $X to get the same results. Chances of that happening? Not very high IMHO. Thew upshot is that if my island nation gets priced out of the oil market and we get into load shedding (rolling blackouts) for want of fuel for the largely oil fired power plants, I will have some electricity most of the time. That brings me to one of my other worries. There's nothing like electric light on a dark night to attract marauding bands of hungry looters, like a moth to a flame!

Alan from the islands

If you've got a decent breeze (10mph+) a fair amount of the time, don't forget the wind generator. Handy for nights/storms when your panels don't work. Even 50 watts (off a cheap 400watt model, which generally don't hit that rating till 25mph+) will run your lights and keep your batteries topped up.

Of course the little ones are kinda noisy. On the sailboat, we turned it off fairly often just to shut it up. Through an exterior wall, especially if not mounted to your house (so no vibration transmission), it's probably noticeable but not really annoying.

I also design, install & maintain renewable energy systems for a living... been doing it since back in the mid 80's before it was the "new greenwashing thing" to do.

DO NOT buy "designs" or systems from one of these money_is_my_reason_for_selling_this_shit.com internet whoresalers. They do not know what they are doing and good luck getting anyone to touch equipment they did not sell, or install and warranty a system they did not design. Ask around and find a reputable contractor that has been doing this for more then 5 years.

Job one is reducing your waste, inefficiency, and consumption. I know it is not popular to talk about conservation... but gigantic, oversized systems on McMansions, to try to compensate for unconscious greed and waste is more of the same thinking that got us into this mess. I will not do a system for a customer until they have done their work first. Most homes can drop an easy 50% off their energy consumption.

Job two is solar hot water. It is much lower tech (and cost) and much more efficient

Lastly, solar PV. There are three kinds of systems:
Grid tie
*Grid tie with battery backup
Off grid

*Battery based grid tied systems are essential for backup during outages, but there is about a 11% efficiency penalty, plus ~25 year life cycle of the batteries to consider.

There (until 2016) is a 30%, unlimited tax credit for RE systems as well as some efficiency upgrades. My wholesale costs are about 50% off of what they used to be... this, along with the federal tax credit means installing a system is about 30% of the price it was about 4 years ago.


By coincidence, I'd spent a good part of my weekend building a spreadsheet on the cost-benefit of rooftop PV. I came to some conclusions that surprised even me; check out the image below (if a TOD Editor wishes, feel free to archive the images in case they disappear):

Click for bigger versions.

Graph 1: 2010 - 2019.

Graph 3: 2010 - 2040.

Some explanations for clarity:

All prices in Aussie Dollars unless specified.

In Australia, we currently have whats called the Solar Credit Scheme, whereby anyone who installs a PV (or Hot Water) designed by an accredited by the Clean Energy Council can generate Renewable Energy Credits. For the first 1.5kW of a PV system, the credits are multiplied by 5, so if you were entitled to 30 RECs, you'd actually get 150. These phantom RECs are treated by the Market the same as the real ones. You can sell them, to bring the cost of the system down to around $4000 (typically, you sign them over to the installer, and they sell them), or you can voluntarily surrender them/destroy them. Any system capacity over 1.5kW can still generate RECs, but only at 1:1 (no bonus).

In my location, a 1kW PV system can be expected to generate about 4.6kWh/day (barring clouds, solar eclipses, Vorlon planetkillers etc)

I made some assumptions in my spreadsheet:

  • A CEC-certified 1.5kW system would cost $4000 after the sale of the RECs.
  • A 1.5kW system with a 5kW inverter would cost $5500
  • 1.1kW of 60W thin-film UL-certified (but not C-Tick certified) panels cost US$1100 (US$0.98/watt). I allowed several hundred dollars for freight and currency conversion, for a total of $1800. For the purposes of the spreadsheet, I am not generating REC's, and am self-installing (there may be a small fee for a sparky to come out and certify the connections are ok). I use the panels to bring the 1.5kW system up to 2.6kW and 3.7kW.
  • A 2.5kW REC-Certified system, fully locally sourced, designed, and installed, would cost $12,000 ($4000 for the first 1.5kW with the bonus RECs, $8000 for the second kW with regular RECs).
  • The Tariff 11 (Residential) is 18.87c/kWh (0.19c for spreadsheet purposes).
  • The Net Feet-in Tariff is 40c/kWh. Note that this is a Net FIT, not Gross, so you only get the 40c/kWh for production that exceeds household useage. For production below parity, you are only offsetting 19c/kWh.
  • No loan is taken out to pay for the system (although Green Loans are available).

For over-parity production (production in excess of household use, thus generating 40c/kWh):

  • 1.5kW system pays itself off financially in late 2013, 'pays' $21/week, and pays a profit of $30,000 by 2040 (30 years lifespan, panels are still probably generating 80% of installed capacity)
  • 2.6kW system pays itself off finalcially in late 2013, 'pays' $36/week, and profits $50,000 in 2040.
  • 3.7kW system pays itself off financially in mid 2013, pays $52/week, and profits $73,000
  • 2.5kW REC-certified system would take until mid-2016, pay $35/week, and profit $43,000.

For under-parity production (production less than useage, thus only offsetting 19c/kWh):

  • 1.5kW system takes until late 2018 to pay itself off financially, offsets $9/week, and saves $10,000 between payoff and 2040.
  • 2.6kW system would take until late 2018 to pay itself off, offsets $15/week, and saves $17,000 between payoff and 2040.
  • 3.7kW system would take until late 2017, offsets $22.50/week, and saves $26,000 between payoff and 2040.
  • 2.5kW 'local' system would take until 2025, offsetting $15/week, and saves $11,000 between payoff and 2040.

As you can see, whether simply offsetting useage, or actually generating income, all PV systems listed actually end up paying or saving the owner a not-insubstantial amount of money over the warrantied lifetime. I have not allowed for an increase in grid power pricing (expected to rise by 25% this year alone where I live), nor the security of supply in case the Grid become unreliable.

For shits and giggles, I also included a 9.2kW system (1.5kW REC plus 7 pallets of 60W TF panels at 1100W/pallet). I haven't put it on the graphs, but it costs $18,000 pays itself off in late 2012, and pays $130/week!

Now, compare the weekly payback if you had simply put the cost of the PV system into a high-interest bank account or term deposit at 5%pa until 2040:

Graph 2: 2010 - 2040.

1.5kW ($4000) gives $17,000.
2.5kW 'local' ($12,000) gives $54,000.
2.6kW ($7,300) gives $33,000.
3.7kW ($9,100) gives $41,000.
9.2kW $$18,100) gives $81,000. If you put in a 9.2kW system and it generated $130/week for 27 years (after 3 years financial payoff), you'd get a whopping $190,000 in 2040!!!

As you can see in financial terms, assuming the FIT remains, it pays to get the biggest system you can possably afford! If you generate more power than you use, the returns you get from a bank, the Stock Market, or your Superannuation can't touch the returns from a PV array. If the FIT goes, as part of budget cuts or whatever, you can take some excess panels down and sell them. After all, once they've paid themselves off, they're pure profit.

Yet, despite this, I cannot get my Olds to install a PV system. They will pay $8000 for a bus to go travelling in, but won't pay a couple of grand in order to save money, despite whinging about the power bill every time it turns up. They will not turn off lights as they leave the room. They will not turn off some of the four fridge/freezers that are running, mostly empty. They will not replace upright fridge/freezers with chest versions. They will not insulate. Etc etc etc ad naseaum. I have hinted, I have cajoled, I have suggested, I have offered to pay to install myself, I have all but got down on my knees and begged them to, at the very least, install 1.5kW. They will have none of it.

If the majority of the Western population has the same attitude (and I suspect they do), then We. Are. Doomed.

My other halfs family are much more inclined to install PV and undertake efficiency measures, but are treading the fine line of insolvency, and simply do not have the funds to do much of anything. I have begun to hint to them, too, that I would be willing to fund the installation of some PV and SHW if they are unable to get a Green Loan, but no luck yet. Maybe when She gets home from her overseas jaunt (ironically, she was supposed to be on Haiti on Monday when the Quake struck, but bad weather kept her on the cruise ship), I can show the family these graphs and change their minds.