Ground Source Heat Pumps

Last week found me at the top table at a conference, having just given one of my “we’re doomed” talks on energy supply to the assembled group. As the conversation flowed around the table, the topic turned to reducing the size of electricity bills that have become a visible marker to the growing problem. Of the eight folk at the table, two had installed ground-source heat pumps, and a third is planning on doing it this summer. Earlier this year, while in Maine, I had a chat with the Bishop* who was considering putting in a system as a means of saving energy (and money) at the church complex.

A couple of years ago I had worked a little on a project that would speed, and reduce the cost, for using vertical wells as the location for the heat transfer pipes, and had given serious thought to putting a system in at home. However in all the cases I have just mentioned the pipes have been laid out relatively horizontally, in three cases in the ground, and in one at the bottom of a pond. With this growing popularity I thought it would be interesting to explain to those of you who don’t know, some of the basics of the concept, while at the same time perhaps drawing better words of wisdom from those of you that have already got systems in place.

Heating and Air Conditioning is, at its most basic, a way of moving heat around. In my search for entertaining bits of video to demonstrate ideas to my classes, last week I watched the “Eat, Drink and Be Merry” episode of Connections 1 by James Burke in which he demonstrates one of the earliest air conditioning systems, as invented by John Gorrie in Appalachicola. It gained him the first U.S. patent for mechanical refrigeration, in 1851, and is the basis for most refrigeration systems used to this day. The initial system (which was not a financial success) used the compression and expansion of air as a means of transferring the heat/cold. As a gas expands (caused in this case, by a retracting piston within a cylinder) it draws heat from the surroundings. Thus by setting the expansion cylinder within a vat of brine, the temperature of the brine can be lowered to 26 degF, which was sufficient to freeze water into ice, or chill the air for the medical wards in which it was placed. Although this original system did not catch the public attention it provided the basis for a subsequent development by Ferdinand Carre, who changed the circulating gas/liquid to ammonia, which did catch on. After the gas has extracted heat in one part of the process it will circulate through the system to a point where it can be recompressed, or liquefied, and in this compression, it generates heat.

In its simplest form, therefore, this circuit consists of a part that radiates heat, and a part that radiates cold, with a circulating fluid/gas that moves (pumps) the heat from one to the other. The efficiency of the process is driven, however, to some degree, by the difference in temperature between the event occurring in the circuit, and its surroundings. So that, for example, if I were using this as a heating system, with the heat generating part inside the house, and the air outside providing the cooling part of the cycle, as the temperature outside drops, so the system becomes less efficient. (Which is why the air source heat pump we currently use is less efficient in winter).

And it is here that the development of the ground source heat pump comes into its own. By locating the pipes for one of the two heat transfer sections in the ground, or deep enough in a pond that the temperature is relatively constant, then a relatively stable temperature source can be formed. With the pipes long enough the circulating fluid will stabilize at the temperature of the surroundings, before being returned to the unit in the house. There, depending on the time of the year, it can be used as a source for air conditioning, or as a source for heating in the winter.

The piping system that goes into the ground can be mounted either horizontally (though it needs to be deep enough to be beyond surface temperature variations), or vertically, or it can be mounted underwater. Systems can also either circulate fluid in a closed pipe system, or can be open in which case they can draw water from a pond/lake/river and transfer heat either to it or from it, before piping it back into the source. The system is claimed to be much more efficient that other heating and cooling systems, the international ground source heat pump association stating:

The GSHP is one of the most efficient residential heating and cooling systems available today, with heating efficiencies 50 to 70% higher than other heating systems and cooling efficiencies 20 to 40% higher than available air conditioners.

. One of the folk at the table talked of having his electric bill cut by more than half.

Now here is the rub, because on my way back from the meeting I gave a fair amount of thought to possibly changing our system. But, over the years we have spent a considerable effort in insulating the house, and, as I mentioned the other day, use a wood-fired tile stove, or masonry heater in the winter, which keeps us warm with relatively little wood, and leaves us, even in the coldest months, with an electricity bill that is less than $300. We live on land that is better for raising rocks than vegetables (there is not a lot of soil cover) so that it seems more practical to look at the vertical pipe version rather than a horizontal layout (and our yard isn’t that large). The cost of vertical systems, so I was told, runs up to over $10,000 – which does not seem out of line with the numbers that DOE provide , albeit for a much larger system than I would need.

Putting these thoughts together it would seem to suggest that my return on such an investment, would be at most $700 to $800 a year in reduced power bills, and while I recognize that power costs will go up, I am not sure that it will be a wise move at this time. But I will continue to look into the idea, and garner more detailed costs – and certainly would appreciate any advice/experience that folks out there might offer.

There is one slight additional thought you might want to consider, the Actress* woke me the other day with an appropriate track from the Beatles Sgt. Pepper’s Lonely Hearts Club Band album, suggesting that our remaining tenure at this place may be a little time challenged.

* For those that wonder at the possible ecclesiastical name dropping, I should mention that I have given family members the same sorts of pseudonyms that I have graced myself with, and so my connections are not, at least yet, that eminent.

Ground source heat pumps are now being installed in around 97% of new builds in Sweden, I understand.

Here in the UK with a maritime climate we don't even nee to go to that much expense as we can install the far cheaper air source heat pumps as it rarely drops far below zero for long periods.
Needless to say the UK government is providing no encouragement or support, whilst in France they put in 50,000 a year.

A couple of alternative suggestions which may provide a quicker pay-back:

You can now buy heat reclamation coils for your waste from hot water.
They are a copper coil, which feeds cold water around your waste, and returns it to your tank heated.
If it is in a shower that is all you need, as the water comes in and goes out at the same time.
If it is for the washing machine or whatever you will need another tank, as the water does not flow out at the same time.

Another system which may provide better ROI is solar thermal panels.
I would suggest the vacuum evacuated tube type, and to insulate them well, as they provide more hot water on cloudy days than the alternatives.

You can buy some which are designed to be combined at a later date with PV panels- of these amorphous silicon is far better in cloudy weather.

You might also consider buying a few square feet of aerogel at $5/foot, as with it you can insulate those areas that are difficult by traditional means, such as the corners of windowframes.

Triple glazing, standard in Sweden, eliminates condensation problems such as you get with double glazing, as it is almost as good an insulator as the wall around it.

Finally, you could consider installing a greenroof, which might be economical when you need to replace your existing roof:
'Green roofs' could cool warming cities - earth - 28 September 2007 - New Scientist Environment

Much better insulation, and they look great too!

You may instead want to explore solar-heated borehole thermal energy storage, as it has been implemented at this subdivision near Calgary, though your system could be much smaller;

See the video for full explanation; Quicktime Windows Media Player

Solar energy is captured year-round by rooftop solar collectors and stored in the ground by pumping the heated fluid into borehole piping loops


This system will provide 95% of the heat for these homes near frigid Calgary. Your system would be much smaller, maybe a couple of boreholes and no tanks. Here's an photo of the actual completed community;

That is a nice project, but it requires a new development with district heating. I think that an individual home could to something similar with a ground source heat pump and solar thermal collectors.

During the summer, the hot water is circulated down into the ground heating the soil and storing the energy. During the winter months, when it is cloudy and you can not use solar thermal heating, you can draw from the heat stored in the ground to heat the home using the heat pump.

Even without solar collectors, ground-source heat pumps store and reuse energy. When cooling the house for the summer, heat is rejected to the ground. When winter comes, that heat can be extracted from the ground to heat the house. As spring approaches, the ground has been cooled after the witner and is thus is a more efficient medium for cooling the house.


Yes, however many places in the U.S. do not require much AC in the summer but require a lot of heating in the winter. Storing a lot of heat in the summer from solar thermal collectors can provide a lot of heat in the winter, saving lots of energy and money.

As the owner of one of the relatively few ground source heat pumps in the UK I can say that air sourced heat pumps are not a good idea even in this climate. The co-efficient of performance (COP), the ratio of heat out to electrical energy in is critically dependant on keeping as low as possible the temperature differential between the hot water in the heating system and the cold water in the underground tubes or air heat exchanger.

Carnot's theorem places an upper limit on this. With a hot temperature at 45°C and a cold temperature at 0°C you could only possibly get a COP of 7 but with a cold temperature of 10°C and a hot temperature of 32°C you can theoretically get a COP of almost 14. In practice you get only a fraction of this value but the drop off in COP with increasing temperature differential is still dramatic. On my system the specification is a COP of only 2.2 for a 0°C to 45°C differential and a COP of 5.2 for a differential of 10° to 32°C. I have installed an energy meter flow meters and differential thermocouples on my system and it performs to specification.

With an air heat exchanger, because of the practical limits on size in a domestic setting, the cold water has to be several degrees below the air temperature in order to suck 10kW or more of heat out the air and without a powerful fan consuming lots of energy the air near the heat exchanger is colder than the normal air further away. The upshot is that with air at 5°C the cold end water is likely to be -1 or -2°C. This has a disastrous effect on the COP and I believe it is common for air sourced units to give up at air temperatures of a couple of degrees or so and turn themselves into resistive heaters. My ground sourced unit has never had the cold end water below 8°C even when the air was -5°C one December night.

The other end of the problem is to keep the heating water temperature down. Conventional radiators of the size common in the UK will not do the job. They are
designed to take water at 60°C or more. Fanned convectors are better but to be able to heat the room to 22°C with water at 35°C requires the sort of heated ares
a you get with underfloor heating. This is no great problem with a newly built house but retrofitting this to an old house as I have done is no small task.

You are usually advised to fit a buffer tank between the pump and the heating system to stop short cycling the pump. With the cheap offpeak electricity available in the UK (my price is 3.3p/kWh offpeak against 12p/kWh else) you can use the buffer tank to store up heat overnight. I would like to experiment by putting phase change material (fancy paraffin wax in the tank to increase the heat storage at almost contant temperature.

Amorphous PV panels are not better in cloudy weather, Monocrystalline are always more efficient. It is just that the differential between them is less in cloudy conditions and they cheaper per unit area.

The very best glazing units are better than a brick wall as they gain solar energy. Averaged over a year there can be a net energy gain.

Of course ground source heat pumps are more efficient than air-source, but they are also a lot more costly to install.

I wonder if your figures for poor performance are looking at the very latest air heat pumps like this one from Mitsubishi?

They have been designed to give greater efficiency at low temperature than was available with earlier models, and also do a bit better with outsize radiators then the old ones, although of course not as well as they would with underground heating.
It is all a matter of trading off install costs against running costs, and having to supplement the heat on a few days a year by switching to electric is probably a better buy for many than having very high install costs.

As for the efficiency of PV panels between amorphous and monocrstalline, sure the latter is more efficient in terms of power by area, but unless you have severe space problems that is not the important metric, as panels are sold by their rated output.

And you are going to get more of that output on a cloudy day from the amorphous silicon, and they are also much better at producing good output when dirty or there are a couple of leaves on them:

As for the preference for vacuum evacuated tubes for solar thermal panels, here is my reference:
Introduction to Solar Power

I don't have natural gas at my home, just electricity, and one of the first things I did was put in an air-source heat pump. For various reasons, I undersized it (and knew I was under sizing it even, dammit) so although I'm unequivocally happy with the unit's performance and reliability, there are still too many days here in Northern California when it isn't up to the job. It's a Sanyo 12KHS51 mini-split model (compressor outside, air exchanger inside; quiet and unobtrusive). Combined with fiberglass frame, double-glazed, low-e, argon filled windows with a spectrally selective film from Bekeart, I figure I dropped my heating bills to half the previous owner's bill.

I'm now looking at replacing my Sanyo with the latest from Fujitsu (but the next size up), the Halcyon. The SEER is 21 (!!) compared to my SEER of just 10. I know that technology won't save us, but it sure does march on...


This conversation is especially timely for me as I will be meeting with an electrical utility to discuss various DSM initiatives now under consideration, including the retrofit of air source and geo-exchange heat pumps in electrically heated homes. As I've stated here before, I've always considered high efficiency air source heat pumps a better value overall, at least in our milder Maritime climate, but I haven't looked closely at the numbers until now.

To better prepare myself for this meeting, I've downloaded ten year's of hourly temperature data for the Halifax area and built a spreadsheet to test various scenarios (it's 673 pages long, but the first two pages are available in PDF format here: According to the Nova Scotia Department of Energy, the spacing heating demands of a conventional new home based on our construction standards and local climate is approximately 50 million BTUs (older homes are rated at 80MM BTUs and an energy efficient R2000 home is pegged at 30MM BTUs). In the standard scenario, I've assumed internal heat gains from lighting, appliances, passive solar, occupants, etc. would be sufficient to maintain indoor temperatures until outside temperatures fall below 15C/59F. I've also assumed heat loss below this point averages 200-watts per degree C (I appreciate heat loss is not linear and other factors such as wind play a large role, but this level of detail goes well beyond my abilities to model here and probably wouldn't alter the final results appreciably).

I selected the Fujitu 12RLQ and 15RLQ as our air source units and estimated their installed cost at $3,500.00 and $4,000.00 respectively (an amount roughly double their wholesale cost).

The ten-year average space heating requirements of our reference home is 15,024 kWh/year. If the results are valid, the smaller of the two units can supply roughly 76 per cent of overall demand and the larger, 79% -- this assumes the heat supplied can be adequately distributed throughout the home, which is unlikely, but that's something I'll put aside for now. Backup heat, to be provided by current heating system, is estimated to be 3,602 and 3,126 kWh/year respectively.

The financials, as I expected, are strong, with annual savings in our base year of roughly $840.00 for the 12RLQ and $880.00 for the 15RLQ. This puts the simple pay back at under four years for the former and five years for the latter, assuming a modest 6% escalation in electricity costs. The internal rates of return are 26 and 23 per cent and the corresponding 10-year NPVs are $4,665.00 and $4,504.00, assuming a cash discount rate of 5%. Overall, a pretty solid investment.

Surprisingly, the numbers for the geo-exchange system were not nearly as good and I'm wondering if I've made some poor assumptions or if my calculations are flawed. I've assumed a capital cost of $18,000.00, which includes the installation of ductwork, an average COP of 4.0 and that the heat pump can supply 100 per cent of the home's space heating and domestic hot water needs. The combined annual savings in our standard scenario are $1,482.00. This provides us with a pay back of just under ten years (again, assuming a 6% escalation in utility rates), an internal rate of return of 1.4% and a ten-year NPV *loss* of just over $3,100.00. I had thought the inclusion of the DHW component would minimize the gap between these two systems but that doesn't seem to be the case. So I'll pose the same question I asked in another forum: Am I missing something obvious or are the numbers I used unrealistic? I don't want to unfairly criticize a technology if it can help customers save money and assist the utility in meeting its goals.

Bear in mind the target homes are electrically heated and would be, in most cases, reasonably energy efficient; again, the space heating requirements are likely to be in the order of 50MM BTUs/year or less. The vast majority would be heated with conventional electric baseboard units, although a smaller number could be in-floor or radiant panel, ETS, electric boilers and forced air furnaces – with the exception of the latter, there would be no existing ductwork.

Any feedback would be appreciated as residential heating systems are not my speciality and I don't wish to publically embarrass myself or my company. And if anyone wants to examine the spreadsheet internals, I'd be happy to email them a copy if they so desire.


I think that I found a flaw. Air source heat pumps output declines significantly at cooler temperatures. More electricity AND less heat as the temp drops. This adjustment is not apparent in your spreadsheet.

In New Orleans, I found that heat pumps sized for a/c cooling load could provide adequate heat down to about +3 C (with interior heat from office building). GREAT for us (rarely below 0C), minimal gas heat supplement.

On an province wide basis, this has strong implications. Minimal demand at 8C (air source works wonderfully), MUCH higher demand (and resort to resistance heat) at, say, -20 C. TOOOO much for grid :-(

If you would like to talk, send me an eMail (click my name and it is in my profile).

Best Hopes,


Check out information in this thread on the new Eco-Cute CO2 air pumps - they are not yet in the States, Japan only, but they are more efficient and good for down to -20C

Hi Alan,

Thanks for your comments and for your kind offer to assist; both are much appreciated and I might just take you up on that.

Actually, the spreadsheet makes adjustments for both output and power consumption based on outdoor ambient temperature. At 8.3C/47F, the Fujitsu 12RLQ produces 4.68 kW of heat and its power consumption is 1.25 kW (COP = 3.75). At 24C, heat output climbs to 6.18 kW, but so too its power demand -- maximum demand is said to be 2.14 kW. At -15C, we're told heat output falls to 0.9 kW; I don't honestly know the exact numbers, but I'm guessing at this point its COP runs in the range of 1.75 to 2.0 and that periodic defrosting of the outside coils kicks us closer to 1.5 or perhaps 1.8. I wish I had better numbers to work with and as soon as I find them I'll incorporate them into the model.

That said, based on published specs, we would expect heat output to rise an average of 0.094 kW per degree C and for our purposes, I rounded that down to 0.09 kW/C. Likewise, for each degree above 8C, power consumption should increase by no more than 0.059 kW and I rounded that up to 0.06 kW. On that basis, I'm reasonably confident our performance estimates are accurate for temperatures 8C and above. When temperatures fall below 8C, we assume heat output drops by 0.16 kW/C which is in line with published specs. With regards to power demand, one would expect it to fall largely in proportion to heat output, but this would be tempered by defrost demand; in our model, I assumed power demand would only fall by just 0.004 kW/C which is far more pessimistic than need be. For example, at -15C, we know heat output is 0.9 kW, but my calculations have power demand at 1.16 kW, giving us a negative COP when, in fact, we know it would be positive. I figured it would be better if I intentionally underestimated performance rather than the other way around so, if anything, the numbers should be even better than what we show here.

Best regards,

at -15 C... but my calculations have power demand at 1.16 kW, giving us a negative COP when, in fact, we know it would be positive.

Actually not. It is entirely possible for a heat pump to generate less heat than electrical resistance heat (COP < 1.0). Given the stress on the equipment, and defrosting, it is better to turn off the heat pump and go to resistance heat (or oil) before this happens (at COP 1.5 or so). 28 F or so depending upon the model.


It is entirely possible for a heat pump to generate less heat than electrical resistance heat (COP < 1.0).

Hi Alan,

I'd be shocked if a heat pump's COP would be allowed to fall below 1.0 within its normal operating range; presumably manufacturers would avoid this for all the obvious reasons. As mentioned, I don't have the operating specs on the Fujitsu 12RLQ (HSPF = 10.55), but I do have them for a York BHX024 which is a less efficient unit with an HSPF of 8.0. At -23C and with 21C dry bulb temperature over the evaporator coil at 800 CFM, the BHX024 produces 2.43 kW of heat and has a power draw of 1.25 kW, which includes the blower. So even at -23C, a full 8 degrees below the -15C cut-off of the Fujitsu, the COP for this particular heat pump is a still respectable 1.95. Defrosting will obviously take the final number down somewhat, but I couldn't imagine a scenario short of entombing the outdoor compressor in a thick block of ice where more energy would be expended performing this task than what would be gained through normal operation.

I tend to believe my numbers are, if anything, unfairly conservative but, again, this isn't my area of expertise, so I would encourage you and anyone else to challenge my assumptions and poke holes in my arguments.


Air Source Heat Pumps are designed to fall below a COP of 1.0 when the outdoor temperature gets near or below freezing. What happens is the outdoor coil begins to Freeze up. Then, to combat this, by design, is the Unit switches to Air Conditioning mode to generate heat on the Outdoor coil, thereby cooling indoors. Then, since it is winter, and you want heat, the resistance coil turns on, thereby taking cooled air and reheating it, and heating it more in order to heat your home. This is painfully inefficient. And is what in fact has given the Heat Pump industry a serious black eye in the majority of North America. And sadly, Ground Source Heat Pumps have had to work hard to rid this stigma, since they are entirely different and not prone to the same problem.

Now I don't know about this fujitsu model. It must use a different refrigerant to make this possible.

Air Source Heat Pumps are designed to fall below a COP of 1.0 when the outdoor temperature gets near or below freezing

Hi Saratoga Peak,

Frankly, I don't see how this is possible and it certainly doesn't reflect my own experience. Air source heat pumps are rated by their HSPF (Heating Season Performance Factor), which is a ratio between how much heat they produce over the heating season versus the amount of energy they consume, in total; obviously, higher numbers are better. The Fujitsu 12RLQ has a HSPF of 10.55 (Zone 4). To convert this to its "seasonal COP", you divide this number by 3.4, which gives us a COP of 3.1. The York product I mentioned above has a HSPF rating of 8.0, so its seasonal COP is 2.4. Just to be clear, these numbers take into consideration the energy used to defrost the outside coils. I should also add that Halifax, N.S. is located in Zone 4 and our heating degree days number 7,800, which means our winters are as cold as those of Minneapolis, MN (not exactly tropical by any means).

Prior to installing my ductless heat pump, I used, on average, a little over 2,000 litres of heating oil a year for space heating and domestic hot water purposes. The following winter, this number dropped to 827 litres and last year it came in at 830 litres. My records show my DHW related consumption during the summer months averages 1.2 litres/day and about 1.5 litres/day during the winter months when water inlet temperatures are lower, I do more laundry (bulker and heavier clothing) and when longer (and hotter) showers are preferred. On this basis, I can reasonably assume 500 or so litres a year can be attributed to DHW needs, with the balance related to space heating. Thus, with the addition of my heat pump, my space heating consumption has fallen from about 1,500 litres/year to 330 litres, for a net savings of 1,170 litres/year. [My home, btw, is a 2,500 sq. ft., 40-year old Cape Cod that has been extensively upgraded in terms of its thermal efficiency, with a space heating demand that places it somewhere between a conventional new home and a R2000 equivalent.]

My oil-fired boiler has an AFUE of 82%, which means I net about 8.77 kWh of heat from each litre of heating oil. Multiplying 1,170 litres x 8.77 kWh/litre, tells me my heat pump is providing me with an average of 10,260 kWh of heat over the course of the heating season. My electrical consumption averages 17 kWh/day during the summer months and climbs to 40 to 43 kWh/day during the coldest winter months when the poor little guy is working flat out. Taking a look at my most recent power bill, here's how the numbers break out (total consumption / days in billing cycle / kWh/day):

For the period ending:

January 08 -- 2,540 kWh, 59 days, 43 kWh/day
November 07 -- 1,527 kWh, 62 days, 25 kWh/day
September 07 -- 1,136 kWh, 62 days, 18 kWh/day
July 07 -- 1,043 kWh, 62 days, 17 kWh/day
May 07 -- 1,848 kWh, 62 days, 30 kWh/day
March 07 -- 2,397 kWh, 58 days, 41 kWh/day
January 07 -- 2,332 kWh, 58 days, 40 kWh/day

Past Year: 10,491 kWh, 365 days, 29.7 kWh/day

Our heating season basically kicks off October 1st and eventually tapers off towards the latter part of May, so if we look at the consumption for just this period, I used a total of 7,548 kWh over the span of some 210 days, which is an average of 35.9 kWh/day. From that, I can subtract what would be used for other household needs (i.e., lighting and appliances) which, based on my summer usage, seems to be in the range of 17.5 kWh/day. If these numbers are more or less correct, my heat pump consumes a little less than 3,900 kWh/year but provides me with just over 10,000 kWh/year in heat. On this basis, my seasonal COP should be in the range of 2.5. Note too that my heat pump has a HSPF of 7.2 and the Fujitsu has a HSPF of 10.55, so the Fujitsu should be, in theory, 1.5 times more energy efficient than my own.

My apologies for the long post, but I wanted you to understand my own "real world" experience with air source heat pumps. I'd be happy to answer any questions you have and provide you with more information if it would be helpful.


Greetings; I am in Sydney, NS and was wondering if you know anyone else in halifax who is researching peak oil ?
You do not have any email contact info in your personal info section. Can you email me ?

Hi Gilbert,

I've send an e-mail to your hot mail account.


Assuming that the 'Halifax' in your handle refers to Halifax, Nova Scotia there is actually an air-source heat pump designed specifically for the Canadian climate, although I realise of course that your climate is more maritime than many areas.

This air-source pump is OK at down to -30C.
Efficiencies should approach ground source pumps, they say.

Here are the details:

The site also includes a cost calculator for different towns in Canada and the US, although the one for Halifax has a glich, as it is under 'Halifax Int'l Airport, which crashes the program.

Hope this helps.

Hi Dave,

Many thanks for the links. I've been following the development of this heat pump fairly closely and I think it holds tremendous promise. As you may know, some of the first generation "cold weather" heat pumps in utility field trials were plagued with quality control issues, but that's not uncommon with any new technology. I hope it will be a huge success for them.

The narrow strip of land that hugs the south-eastern portion of the province stretching from Yarmouth in the south to Halifax in the north is considerably milder than other parts of the province; we're rated as Zone 4 whereas the rest of Nova Scotia is classified as Zone 5. In fact, our temperature here at harbour side are commonly two to three degrees warmer than even the airport readings just a few km inland.

I log every single hour my heat pump operates in a spreadsheet and calculate its relative performance based on these airport readings. I estimated my seasonal COP last year at 2.48; in reality, it's higher than this due to our slightly milder micro-climate.

The nominal COP of the Fujitu 12RLQ is 3.75 (at 47F/8.3C) and based on airport data for the past ten heating seasons, I've calculated its seasonal COP to be 3.26 (and as I've stated above, I believe my estimates are decidely conservative). I suspect one reason why our performance is so good is that given our truly maritime climate, we seldom get sharply bitter cold weather, and when we do, it doesn't last very long. In addition, we have unusually long, cold spring. Whereas Toronto come May can be basking in 30+C temperatures we consider ourselves lucky if we break 15C. Looking at the rolling COP as each day passes, you can clearly see how our extended heating demand during the months of April and May move our seasonal average upward.


Hi Paul.

They are not available outside Japan yet, but if you have concerns regarding the reliability of the Canadian model you might possibly have more confidence in Japanese engineering, with the added fact that they have installed very many of their new carbon dioxide based Eco-Cute heaters for several years.

The big thing is that they have a COP of up to 4.9.

Here is the data:
Technology and Market Development of CO Heat Pump Water Heaters ...

I don't know how that would fit into your schedules but it might be worth waiting, as I believe they might be available outside Japan in the next year or so.

That they are good for down to -15C can't be bad either, even if not strictly needed in Halifax.

Hi Dave,

I think they're just now hitting the European marketplace and I suspect they'll eventually make their way here, but it likely will be a few more years yet. Someone in another thread spoke of "technological hard ons" and I confess there are two things that stir deep passion; one is this: and the other (don't laugh) is the Eco-Cute. As someone who abhores energy waste, I'm ashamed to admit the former, but the '74 Challenger was my first set of wheels and thirty-five years later, it still holds tremendous emotional appeal... chalk it up to that left-side, right-side of the brain thingy.

In any event, I would dearly love to replace my oil-fired boiler with an Eco-Cute. I believe Sanyo recently announced an enhanced version that works efficiently at temperatures at or below -20C. Pardon my Japanese, but that really "蹴りのろば!

At this point, almost two-thirds of our fuel oil consumption is DHW related. Five hundred litres/year is a trivial amount compared to most households, but since it's the only low hanging fruit remaining, it's the logical place to target. I'm struggling with this, but I'm thinking of adding a Nyle heat pump to take on this responsibility, assuming I can somehow attach it to plumbing that connects my boiler and the SuperStor Ultra cylinder.

For information on the Nyle heat pump, see:

Right now, I can shoot down to Bangor and throw one in the back of the Chrysler for a little over $800.00 CDN. With a COP of 2.0 to 2.4, it would cut our water heating costs by more than half, plus minimize or even eliminate the need to run the dehumidifier during the summer months (after our heat pump, probably our next biggest power draw). Between May and October, our dehumidifier averages between 5 and 10 kWh/day, so the Nyle could assume full responsibility for this task and, in the process, provide us with free hot water. Even though our DHW requirements are extremely modest, once you factor in the dehumidifier savings, our simple payback is less than three years. My unnatural lust for the Eco-Cute is the only reason why I'm hesitating. ;-)


You obviously know a great deal more than I on all these subjects!

On top of that, the requirements are radically different between America and Britain - no need for de-humidification here, and not much for air-conditioning.

One thing which caught my eye though was reclamation of heat from waste water via a coil - at the cost of your bills it won't pay-back in a reasonable time though.

Hi Dave,

I had considered adding a heat recovery device to our shower drain but there's only the two of us and our low-flow shower head has an on/off control that allows us to conveniently turn off the water as we soap up, so a typical shower might consume 20 to 25 litres of hot water at most, and I suspect the actual number is closer to 15L. That's less than 1 kWh of heat demand and if a recovery device could recoop 40 per cent of that, our savings would be less than $3.00 a month; strictly on economic terms, a non-starter.

As an alternative, I heat our wash water during the summer months with a 50 metre garden hose that I roll out on the back patio. An hour exposed to direct sun can raise water temperatures by 40 or 50C. And by the time the front loader has finished its first load, the hose has come back up to temperature and is ready to do the next. By scheduling laundry on the days when the sun does shine (admittedly a daunting task given our maritime weather), I've trimmed our fuel oil consumption between May and October by an average of 6.0 litres/month, and at no cost to boot! It's enough to bring tears to any Scot's eyes. :-)


The efficiency of these devices is limited, according to thermodynamics, to the temperature differences between the house and the medium from which the heat is being extracted. Sure air pump heat pumps are as efficient as ground source heat pumps when the heat source has about the same temperature ( i.e., 50 degrees F). But as the air temperature drops, then air source heat pump efficiency and capacity drops through the floor. Employing tweaks to improve the efficiency of air source heat pumps should help ground source heat pumps as well.


Hi Retsel,

I've been discussing the performance of GSHPs with a professor of architecture and engineering at the University of Waterloo. He's done extensive in-field evaluations of these products and tells me the COP numbers are often significantly lower than expected, particularly where heating and cooling demands are not well balanced (in my province, for example, our heating season spans late September/early October and runs through late May/early June and we have no cooling requirements to speak of). In addition, during the shoulder seasons, daytime air temperatures routinely exceed ground temperatures, especially late spring when ground temperatures are at their lowest due to natural thermal lag and where the earth in the immediate area of the supply lines has been further chilled by the operation of the GSHP.

Along these lines, the ten-year mean air temperature for Halifax for the months of October and November and April and May is 7.2C (as noted above, the Fujitsu 12RLQ has a COP of 3.24 at 8.3C and 7.2C is within spitting distance of that mark). The ten-year mean temperature for the full heating season which, for our purposes, I've designated as October 1st through May 31st is 2.2C. According to Natural Resources Canada, our average "deep ground temperature" is 9C and I presume this number is somewhat lower during the winter months due to normal seasonal variations and would fall further as heat is extracted over a seven or eight month period. Looking at the entire heating season, the spread between air and ground temperatures may not be as great as one might think.

In any event, if we assume a heat demand of 15,000 kWh/year, at $0.10 per kWh, a homeowner would expect to pay $1,500.00 a year to heat with electric resistance. A high efficiency air source heat pump with a HSPF of 10 would lower this cost to $500.00/year and a ground source heating system with a COP of 4.0 would get us to down to $375.00. The additional savings, in this case, are $125.00, and if we add another $250.00 for domestic hot water, our net savings are $375.00. If we double heat demand to 30,000 kWh/year and double electricity costs to $0.20 per kWh, our incremental savings reach $1,000.00/year ($500.00 for space heating and a further $500.00 for DHW production). It sounds great, but if the installation costs are $10,000.00 or more above what I would expect to pay for a conventional air source heat pump, how do I stand to benefit?


You live in a similar latitude as me as I live in Ann Arbor, Michigan. The efficiency benefit of a ground source heat pump (GSHP) over air source heat pumps (ASHP) are obvious and you seem to agree with that, although I did not verify your numbers. I will then address several points that you make.

One is that with a closed loop GSHP, the ground will tend to be cooler at the end of the winter (perhaps approaching freezing or 32F) and thus an ASHP would actaully be more efficient than the GSHP. That is potentially a true statement for the daytime but as long as the nightime temperatures are low enough, the GSHP would still be more efficient. If you are talking about when the nightime temperatures are also higher than 32 degrees even at night, the energy gain from solar heating though is likely high enough that neither system would run much at these higher temperatures (remember that insulation is sized to deal with zero F degree days), thus this warmer part of the year would have very little impact on costs. Just a sidenote, my lot is adjacent to a pond so the water table is VERY high. I doubt that the ground temperature will decrease to under 40F for my system because of the very high water content in the soil.

An important point to make is that the impact on global warming will tend to shift our climate. We will spend more of our energy on cooling going into the future compared to heaating, thus at our latitude, the heating of the ground will be more balanced with the cooling of the ground. Also, the solar affect tends to increase the cooling load for the summer months greater than what the average temperatures would suggest.

All this discussion is moot if the GSHP is an open loop system, which has improved thermal efficiency but trades off with pumping losses.

I will not agonize whether your cost numbers are right or wrong. Using them on their face value, the economics suggest that the payout for a GSHP at current energy prices over an ASHP is on the order of 30 years. This is not that much different than a GSHP over a natural gas furnace with air conditioner. It all depends on whether you want to trade higher capital costs for operating costs.

The second part of your message gets closer to the issue for me, and that with energy prices expected to increase, the payout is expected to be, using your simply adjusted cost numbers, 10 years or less. That is a much more easy step to take when installing a system cost that is expected to last over 30 years. The other part of this is that I am an environmentalist. Thus I gain a sense of satisfaction on the fact that the GSHP will reduce greenhouse gas emissions over a natural gas furnace or an ASHP. By that way, assuming coal-fired electricity generation, the ASHP will have a larger CO2 impact than both GSHP and natural gas furnace/air conditioner. Even assuming coal-fired electricity, the GSHP will have lower CO2 emissions than a natural gas furnace/air conditioner.


Hi Retsel,

Thanks for your comments. As is true with most things in life, we're often forced to make trade-offs and, in this case, I'm willing to sacrifice some efficiency for lower price -- the exact numbers we could probably toss about for days. I decided my limited resources would be better spent elsewhere (i.e., improving the overall efficiency of my home's thermal envelope), but if someone is willing to spend more for a system they percieve to be better for whatever reason then, obviously, price may not be the best metric by which to judge such investments. I certainly applaud you for taking into consideration these other factors. However, as valid as these other points may be, if we are to recommend a particular technology and especially if we are to recommend it over a competing technology, we can't ignore or simply gloss-over the financials. No one has properly addressed this aspect, at least to my satisfaction, and in the absence of such, I can't in good faith recommend these systems.

BTW, just as one more random data point... earlier today I asked a contractor who installs these products in the Moncton area (in the neighbouring province of New Brunswick) how much a 3 tonne GHSP might cost. He said a typical closed loop system in the case of new construction runs in the range of $25,000.00 and an open loop version might push us closer to $30,000.00. I'm curious, do these numbers strike you as high, low or just about right?


Triple glazing, standard in Sweden, eliminates condensation problems such as you get with double glazing, as it is almost as good an insulator as the wall around it.

IIRC double glazing (not high E) is around R1.5 while triple glazing runs around R3. This is hardly 'almost' as good as a 6" wall at ~R25 - 30. Not to say of course that triple glazing is not a good idea.

With krypton gas fill and the right low-E, a triple-pane can reach R-7.85 (and I've seen higher);

Still nowhere near as high as a decent insulated wall, though.

"Still nowhere near as high as a decent insulated wall, though."

Because a window lets in sunlight and a wall does not, it is possible during daylight hours for a window to let have a net energy gain which a wall cannot. If the walls inside of the insulation have a high thermal mass this energy can be stored at least overnight. This is used in passive solar houses. Experiments have been done using micro-spheres of phase change material incorporated into a thick plaster coating of the wall to increase the thermal mass of interior walls as the waxy material absorbs a large amount of latent heat in warming up over a few degrees around its melting point.

The British Fenestration Rating Council has a rating system that combines the insulation value with the solar gain factor and any air leakage in opening windows. A positive rating means a net energy gain over the year and a negative value a net energy loss. With low iron content glass to maximize solar gain and soft coated low emissivity glass triple units with Xenon gas fill and the best spacers a positive rating is possible. The metric U value of such units can be as low as 0.7 W/m².K (Imperial R = 8)

> Because a window lets in sunlight and a wall does not, it is possible during daylight hours for a window to let have a net energy gain which a wall cannot.

Absolutely. Which is why I designed my house using passive solar techniques.

>With low iron content glass to maximize solar gain and soft coated low emissivity glass triple units with Xenon gas fill and the best spacers a positive rating is possible.

That depends on where the building is located (i.e., Los Angeles vs Chicago vs. Anchorage)

>The metric U value of such units can be as low as 0.7 W/m².K (Imperial R = 8)

Such windows tend to have relatively low solar heat gain coefficients (SHGC), significantly reducing the incoming solar heat. I favor dual pane (with minor low-E) with insulated window shades of one kind or another, even if it means raising them on sunny days and lowering them at sundown. My house is in a moderate temperate environment; if I were in Calgary, triple pane might make more sense, at least on the north, east, and west windows. I would still use insulating shades, but that's just me.

Be wary of argon filled windows. We just spent $7,000 for installation of 7 of the best high efficiency windows, only to find out that on average, about 5% of the argon leaks out each year. If I had the money to spend over, I think I'd get removable internal and external acrylic storm windows attached with magnetic strips that can be removed in the summer.

Please share more info about these windows with
"removable internal and external acrylic storm windows attached with magnetic strips that can be removed in the summer"

Any links to manufacturers or sources?

Sounds like an interesting solution to the problem double-paned windows eventually loosing their seals and foggy up (and dropping the efficency).

Greg in MO

I was using 'very near' pretty casually - meaning that you would not have the usual condensation hassles of double glazing, which would bug most people and in a house with high standards of insulation and low air turnover, for example in the mechanical system used in the Passivhaus, condensation would really be a problem.

We had our heat pump installed in our Brittany home in August last, to replace 25 year old electric radiators and underfloor electric heating loop, (installed by the previous owner, an EDF employee, who's 35 euro a month fixed electricity charge encouraged such inefficiency). We had paid as much 300 Euros per month to shiver through winter months with the old system. Heres a summary of the geothermique pompe a chaleur's costs and specs. The 13.89kW heat output rated system uses a KSB bore hole pump to transfer water at 42litres/min and 11 to 13C through the heat pumps evaporator -water/refrigerant (R134a)heat exchanger, then back to ground remotely at depth.
(Drill wells for heat pumps aren't always applicable, access to RUNNING water in the water table is usually required- (the alternative is digging up twice the surface area of the house and burying refrigerant or water pipes in the garden 1 m down), still water reservoirs temperatures/level will gradually fall, reducing the heat pumps coefficient of performance, and useful heat produced, icing of the evaporator heat exchanger eventually results, preventing operation.
In our case the prior survey consisted of a silver ball on a chain: I was assured that such divining never fails(ca marche chaque fois), and sure enough at 40 metres depth the drill bit reached water. The return bore hole was drilled remotely to a depth of 34m.
The bill for the initial survey, and 2 men, with impressive kit for a days drilling, and capping of bore holes was 4827 Euros. The bill for the fully installed system including bore holes was 27715 Euros, including around 10000 Euros for around 15 high surface area* radiators, (*which compensate for the circulating water raised to only around 42C). The Erset system is rated at 13.89kW heat output, sufficient for 200m2 living space, with a 5.7 COP (the refrigerant cycle will have evaporator temperatures around 8C, and condenser temperatures around 47C, the compressors power absorbed derives from the saturation pressures' ratio ), ie. 2.5kW input to the heat pump (assuming 13C ground water, not including the circulating and bore hole pumps power consumption) We did make a B movie of the caterpillar tracked drill rig, and associated diesel engine driven air compressor, in action, it would make a good episode of Thunderbirds, but the caterpillar chewed up the garden.
Next on the agenda for this year, is a conservatory for passive heat gain, a second wood burning stove this time with integral water coil, inconjunction with a couple of solar thermal panels for year long hot water.

I have noticed this in the queue for a few days, and have been looking forward to it. I have been investigating them myself. My brother was going to get one, and the heating and cooling guy said that lifetime maintenance was probably going to be costly. I didn't know enough about it to challenge the assertion.

My understanding is they get about as much maintenance as the typical fridge.

I do understand that they work best with underfloor heating, so that lower temperature water (~30C) can be used. If you don't have underfloor heating, then ...

I've been considering the general area of heating/cooling for quite a while, since its the real elephant in the room of home based energy use. My aim has been to find some affordable solutions which can meet the need. GSHPs are one, but with a typical efficiency of 400% (due to the heat engine) they still demand so serious kWh to run. There are others which are looking more interesting, but either way home insulation is the first question to be addressed.

That is correct. The Waterfurnce guy said the same thing. Very little if any maintenace. The piping is either all copper or PVC. The joins are all perminently sealed and burried.

They give most benefit when you have underground heating, but can also be used by installing oversized radiators, about 20% bigger than normal, but at reduced efficiency compared to underfloor.

You should also take care that the system you install is compatible with the later installation of solar thermal panels to further reduce bills.

We had previously installed a heating loop that included solar roll on the roof, and a heating coil around the firebox of the tile stove. The fluid then went into copper pipe under the floor (this was a house extension) and there was an extra insulated reservoir underground outside the house. I had placed thermocouples around the circuit and monitored it for a fair while. The first thing to go was the reservoir - we never built up enough heat that it had any value. The underfloor heating required the stove to be run at high temp all day to get the floor up to comfort level, and it appeared to have a small leak. The combination caused me to disconnect that bit next. We ended up with the system providing pre-heat for the water in the hot water tank. It raised it about 20 degrees as I remember. (We did this 20 years ago and I have lost most of the records). Having the tile stove at the bottom of a circular stair that led back upstairs gave us a natural heat circulation system that was, inadvertently, the most most effective part of the whole system.

hey robert,

i installed a GSHP in 1994 in my new, well insulted house in your old neck of the woods in MT. our electricity costs are very low at 5c per KWH . it uses about 5000 KWH per year, which translates to $270 per year heating and cooling. my last electric bill for the month of january in an all electric house ( even electric HW!) was $80. no maintanence and a air to air heat exchanger for good quality inside air.

On the cost issue, I expect electric rates to take a large jump. NG drilling in Canada has slowed because current prices are less than drilling costs. NG stocks are falling. Laherrere has predictions showing a steady decline from here on out based on reserves found. We really need accurate cost estimates from the EIA (yes, I am dreaming).

Like Robert, I wonder about the lifetimes of these systems. Iron and steel rust underground. I have seen what tree roots do to sewer lines with even tiny leaks, they pry their way in following the water. Are there technology choices that are going to result in longest life? Is it possible to drill and then run aluminum (or some other non-corroding metal) down the drill hole?

Typically I believe the ground loop piping is done with PEX as a single piece of pipe (i.e. no underground joints). Longevity should be quite good unless the ground shifts or something else physically compromises the pipe.


Yes, the ground loop is heavy-duty plastic tubing (I don't recall offhand what the material is). For vertical loops, the U-shaped fitting is fused on at the factory, and the loop is delivered to the job site in a big roll. Any connectors that need to be installed to complete the loop are thermofused in situ.

The Piping used in the ground should always be PE Pipe, or Polyethylene. Good for 50+ years. Never use PVC or copper underground. And as GSHP gains popularity, never let anyone sell you a DX or Direct Exchange where the copper coil goes in the ground. The refrigerant WILL leak out. Not that it has been mentioned here yet. Just a word of caution.

Most refrigerants are greenhouse gasses by the way, so we don't want ANY leaks, ever.

If your aircon needs refilling you have dumped a load of CO2 equivalent into the atmosphere for a very long time.

And in fact a multiple effect of CO2. Essentially, a kg of refrigerant is 10 - 20 times the greenhouse effect of 1 kg of CO2. Maybe worse, again, I don't have the numbers in front of me.

To say nothing of ozone!!!

I know two people with these systems and I am less than impressed. The lady with the first one went away for two weeks in the winter, leaving it on low to avoid freezing the pipes. When she came back she was greeted with an electric bill of over $1000. The compressor had failed and the backup electric heating coil went on constantly. This is the problem with all high tech solutions, they work great until they break at which point all the savings go down the toilet. The other system hasn't had any reliability issues but it hasn't really shown massive savings either and is inferior to gas from a comfort point of view especially when the temperature drops below -5C.

Building new houses with these systems is just a waste of time. The real answer is super insulation. If you build it right you just don't need a big heat source. Insulation is infinitely more reliable and not susceptible to electricity price fluctuations.

My understanding is that ground-source systems have to be properly sized for the house. If the ground loop is not long enough, the circulating fluid will not absorb enough heat energy from the ground by the time it gets back to the heat pump, and the compressor will not be able to deliver warm enough air, so the auxiliary heat kicks on. For three weeks in February 2007, it never got above 22-23 degrees F at night, yet our geo system delivered warm air and never went to emergency heat. And, as you mention, good insulation is a must, too...

Do be careful sizing the units, GSHP's do not require a backup electric coil unless you intentionally Undersized it. Otherwise, you should size the unit to meet demand of the coldest design day. No Energy sucking backup coil required.
Also, there are several options for coupling to the ground, each one needs to be weighed based on site conditions for cost effectiveness.

Before I begin, just one piece of info for those that don't know. Heat pumps are rated by the "ton of capacity" and 1 ton = 12,000 btu/hour

Also, I live in upstate NY and have a 3 ton Geothermal heat pump heating my 1450 sq. foot 2 family home. My tenants have Hot water baseboard, heated by my unit, and I have radiant floor. This is my first season and I am very happy. At $0.15/Kwh my heat has cost me to date $300.00 for the whole house.

I educated myself extensively, and took the 3 day IGSHPA Installer course to become certified. And learned a wealth of knowledge as well. Very worthwhile.

First, Open Loop systems, where ground water is extracted and returned responsibly. These are the most efficient since the fresh water is always near the average ground water temperature.

The First choice is a standing column well, which is an open loop system, where water is extracted from a normal domestic water well, and 90% or less is returned to the same well. This requires a dry well or another place to return the other 10% of the water to the ground. This is what I have and I used my existing well. The well for this system should contain a water column 60-80'per ton of capacity. I have a 3 ton system, and a 240 deep water column, so this worked out perfect, and in fact I got lucky.

The Second choice is a 2 well open loop, shallower wells are drilled, generally in an area with a high water table, sandy or permeable soils, and a long way to bedrock. One well must be rated to meet the GPM for your system, usually 2-3 gallons per minute per ton (varies by manufacturer). Then the second well, an appropriate distance away is the return well.

Next are closed loop systems,
The rules of thumb here, for each ton of capacity, you want 1000' of pipe in the ground. And a parellel piping layout is needed to save on pumping costs.
A horizontal system, where you spread the pipes out underground at least 6' deep is the most intrusive into the landscape.
A vertical system is where you drill 500' bore holes/ton of capacity, and you place the tube with the U connector at the bottom giving you a 1000' of ground coupling.
Then the pond loop, you can save on some piping here, I don't remember the amount per ton, but the pond must have an area deeper than 4 feet greater than the area of the space you are heating.

Closed loop systems are less efficient because as the season progresses, the field actually cools off, sacrificing some efficiency,
Also pumping the fluid through all that pipe is more costly than the more open flows of an open loop system.

I took a 3 day class on this, so research and consult with people, these are very good systems when installed properly. But very worthwhile.

Super-insulation is surely attractive. Perhaps its biggest challenge is adequate ventilation. A oounter-flow heat exchanger would seem to be the ideal solution, but maybe not. I don't see residential units advertised widely, though perhaps I just don't read the right magazines.

Some years back I was thinking of building a heat exchanger. The problem that occurred to me is that the surfaces are likely to get all gummed up and moldy. Outgoing air gets cooled so moisture will condense. Or incoming air in a Louisiana summer. So I would expect that maintanence of those heat transfer surfaces would be a significant burden. I would love to learn from the experiences of others!

My understanding with ground-source heat pumps is that their suitability depends a lot on soil type. I think the soil needs to be wet and probably there needs to be decent water flow. I think that heat conductivity in soil tends to be very low. Once you've pumped the heat out of a chunk of soil, how long will it take to warm back up? Of course, it's great if warm water comes flowing by! But then one has to wonder a little about the housing density. At some point, the water flowing by may well have been cooled already by the neighbors up the hill.

They work fine for high density and apartment blocks in Sweden, but then they are designed in the expectation that all the other houses will have ground source heat pumps too.

Once the "looper" (ground-loop installer) inserts the tubing in the vertical well (for a closed-loop system), the backfill is typically done with a bentonite clay grout, which improves the thermal conductivity of the surrounding soil. The installer of our system said that thermal "charging" of the soil is not really a problem, as long as multiple well bores are at least ten feet apart.

duh, you gotta insulate. they only work well in a well designed and insulated house. they are only capable of raising inside heat 20 deg. F , so they need to be fitted to the heat loss of the house. our house has R-35 walls and R-55 ceilings. basement is also well insulated to super good cents level. the system was designed by the subcontractor and that's all they do is install GSHP. system works great, house is super comfortable and january's electric bill for an all electric house was $80. temps reached below zero F for a few days. higher tech yes, but it's only a fridge working in reverse.

Absolutely correct. Check "superinsulation" in wikipedia. I live in Red Deer, Alberta, where just a week or so ago, we had -50 degrees celsius with the wind chill. When the natural gas disappears, superinsulation will be the largest part of the answer -- combined of course with some sort of ground based pump or seasonal storage system like Okotoks has.

How well would ground source heat pumps work if electricity is available for only a few hours a day? This could happen either because of standard rationing procedures, or because electricity is only available when there is enough sun or wind to provide it? Would it be better than other systems in such a circumstance?

Because people's lives depend on electricity, there will be little or no rationing to homes. Maybe stores and offices, but not homes. All a politican needs is someone freezing to death in their home because their power was rationed.

A general or a dictator, however, would merely make some comment about needing to break a few eggs to make an omlette.

Shows we need to get those nuclear power stations built asap. Though electricity will be least effected by peak oil.

Though electricity will be least effected by peak oil

I strongly disagree. Actually I think electricity is already getting affected by peak oil, though more or less indirectly - watch the electricity shortages in China, South Africa, Albania, Central Africa etc... These are either directly linked with rising oil&NG prices - as is the case of diesel powered African countries, or more indirectly - like in China or South Africa. Traditionally oil has been the fallback fuel in case there are disruptions in the predominant energy sources - the inability of SA or China to go to oil&NG to cover their coal shortages is a direct result of their high prices, which in turn is a result of their growing scarcity... it is a cycle in which the substitution of one energy source with a second one exerts too much pressure on the letter and so on. And this is only going to be getting worse with the advent of PO.

It's only a matter of time until similar developments start occurring in more developed countries - UK comes to mind as the first one to watch for...

Though not technically peak oil, electricity will be especially affected by peak natural gas.

I expect natural gas production to be increasingly stressed in the medium term, both for economic and environmental reasons. In my view the situation will become dire after the moment NG peaks and starts declining (and it tends to decline precipitously). Unlike oil, NG is generally not wasted in conspicuous consumption and when it starts running short the consequences will be much more devastating.

"Unlike oil, NG is generally not wasted in conspicuous consumption and when it starts running short the consequences will be much more devastating."

Many homes can get new furnaces, insulate, turn the heat down and etc. if a recession happens we could have less demand for natural gas from factories, buildings not used and etc.

Just on the following aspect of natural gas use I would go along with LevinK,

In 1999, the average price of natural gas was $2.19 per MMBtu, close to the past average natural gas price for the last 15 years (divide the cost per MMBtu by 10 to get the cost per therm of natural gas). It rose to a $4.40 average in 2000. At a price of $2.19 per MMBtu, the cost of producing ammonia is about $100 per ton. Recently, the spot price of natural gas spiked to $10.00 per MMBtu, which would translate to an ammonia production cost of approximately $360 per ton. At that cost natural gas accounts for more than 90 percent of the total ammonia production cost.

Seems a lot that gas is being burned off in the tar sands producing oil, maybe we could reduce that by not driving to the burger bar? We could walk there and lose a lot of weight and take the whole family even, converse along the way, get to know each other, maybe include the non custodial parents, Wow it could be Father Knows Best land Revisited... Gee, Beaver, I can hardly wait for natural gas to do a dump.

Actually I think electricity is already getting affected by peak oil, though more or less indirectly

anything other than indirectly is a stretch. china and south africa have as much or more to do with mismanagement by government and the weather than anything else. it seems like both china and south africa want to keep electricity below market rates. the outcome is very predictable. this is not the first time energy prices have gone up.

One of the reasons I am asking is because Euan Mearns has been writing about the serious issue of electricity availability in Britain in just a few years, because of likely natural gas shortages. This is his link to Daddy, will the lights be on at Christmas?. Since Great Britain is one of the places where heat pumps of various kinds are being discussed, and since the ground source heat pumps have long life times, I think this is a question people should be asking.

I don't think we should be complacent about electricity in the US either. We have built very few coal fired power plants since 1990. Now, with the concern about global warming, and unwillingness of major banks to finance them, it is unlikely that coal fired plants will be built in the future either. Instead we are getting more and more natural gas (far more than wind, over the years). If we have a natural gas problem, electricity will likely be affected, especially in vulnerable parts of the country (North East, Florida, California). Upkeep on the grid, and needed enhancements to the grid, are other issues. See my article, US Electricity Supply Vulnerabilities.

I think the plan is to cut businesses off first, but this may not work. If there is a grid problems, everybody may be out, or the amount of electricity may be very low. We have already had problems with electrical shortages in California in 2001. We shouldn't be too surprised to see more in the years ahead.

Gail, a study this week commissioned by the Government has alleviated my concerns about wind power in the UK:
It shows that the resource tracks very closely to use, with output two and a half times summer output in midwinter

This also indicated that connection and back-up costs should be affordable.

Furthermore, we have good prospects for reducing intermittency by the use of tidal lagoons, which themselves should generate 2.75MW of power:

A test lagoon is planned:
Tidal lagoons

In addition to these factors, although ground source heat pumps may be preferable we have a climate which is well suited to the far cheaper air source heat pumps.

All that doesn't mean that we won't have supply interruptions though, as we have very little emphasis on conservation, and no real plans to upgrade our housing stock.

"We have already had problems with electrical shortages in California in 2001."

california was robbed. it wasn't an electricity issue.

Ummm... there were power problems in California and judging by the current experiences in Pakistan, South Africa and many other countries there will be again if adequate steps to ensure supply are not taken.

It's just like oil, there are many causes for the lack of supply, it doesn't really matter what they are. We are going to have to live with the inconvienient consequences.

Eventually, any power will be mostly intermittent electricity since that is what sustainable power systems usually produce.

The reason we don't use sustainable alternates to FF at the moment is their extra cost and complexity - in the future energy won't be cheap any more, things like heat pumps are way more complex than a wood fire!

So, for efficiency we will need to use heat pumps - if we can afford them! - we may need the money for food, not space heat!

Plan for a future where you need minimum heat and don't need to maintain anything complex - that means things like insulation. That is how around 5 billion people are living already.

Enron gamed the system in California. They were selling power outside the state to create shortages. They also created shortages by taking power plants offline. There were permits issued for power plant construction before Enron, but when there is deregulation that allows gaming, then producers sit on the sidelines. California has done more to use electricity more efficiently than most other states in the last 20 years. It is good to set the story straight with facts, rather than have rumors.

The thermal mass of the house interior and furnishing can but used for thermal storage, if you don't mind allowing higher temperature swings, or thermal mass could be added in the form of rocks or a warm water storage tank to avoid temperature excursions.

With future electricity from wind and other variable sources, thermal storage for cooling and heating will prove much more cost effective than batteries.

How well would ground source heat pumps work if electricity is available for only a few hours a day?


I have seen ice banks here in Southern California which were designed for off-peak energy usage. Southern California Edison gives us a break on the power costs in exchange for the time of day restriction.

The one I am most familiar with is an outside unit, has about 5 tons storage, and makes ice at night when air temperatures are closer to dew point. 1 AM to 4AM are prime hours to make ice.

During the day, water at around 34 deg F is circulated from the bottom of the ice bank, through valence heat exchangers in the building, then returned to sprinkle on top of the remaining ice. The amount of heat to be removed from the sanctuary and church offices is controlled by modulating circulating pumps.

There are no fans in the building. Absolutely quiet. And works like a champ. ( Disclaimer: the system was designed and installed by a genius friend of mine - and I admire his workmanship and design skill immensely ).

That is interesting - it is not too surprising that someone figured out that electricity might be much cheaper at certain times of day, and that it would be good to be able to store the coolness as ice.

I looked up ice bank and found this abstract from a patent:

A multi-mode off-peak storage heat pump system for a building which includes a unidirectional flow refrigerant circuit and a brine circuit in selective heat exchange relation with one another, each being connected to a dual coil in ducts wherein air can be circulated within and between the inside and outside of the building, and an ice bank in the brine circuit for coolness and low-level heat storage, the system providing heating and cooling with no refrigerant reversing valves or coil defrost means and with optimum off-peak power utilization.


the answer is it depends on how much electricity you have . they will NOT work on a solar system...uses too much juice..unless you have a huge solar array or enough windmills to be dutch. on an intermittant electric schedule, it would depend on how well insulated the house was , outside temps,how much yo-yo of temp you would put up with, etc. with little electricity, i would install a wood stove.

The system I'm looking at putting in this year is a WaterFurnace. They started in Ontario but now have their factory in the US. Combined Federal and Provincial government programs will kick in $9,000 in grants for a GSHP. Total cost for a vertical well system here is about $20K.

I'll be going verticle for 2 reasons. First the water table here is only 20 ft down and goes as deep as 300 ft. We are sitting on one of the largest aquafers in the country. Thus recovery time of the well pipes will be quick. Recovery time is important. If the pipes are not long enough it will take too long for them to recover to gound temp from a draw, hence you loose efficiency.

The rule of thumb is one linear foot of pipe for every sqr foot of house (for closed systems). Thus for horizontal one would need 1000 linear foot of excavation, 10 ft appart from each loop, down some 5 or more ft. That is a tremendous destruction to one's property. Fine if you have the land or building new, not for someone who has a large veggie garden and trees. So that was our second reason for going verticle (6x 150ft each, filled with glycol).

The system will actually heat two structures. When it is not heating the house it will swtich over and heat our greenhouse. Thus allowing us to grow food all year round. We will be super insulating the house so it will spend less time on that heating and more on the greenhouse.

Cost is immaterial. If we are heading into shortages of natural gas and home heating oil, then the installation of a GSHP is priceless.

We hope to get ours in by the fall of this year.

Canadians get $9000 in rebates?? Wow. You lucky ducks -- Uncle Sam is soooo cheap... We only got back about $1600.

A $9k rebate is very special.
You have to be upgrading an old A/C at the same time and get grants
from both the fed and the provincial government.

That does reduce payback to around 15 years or even 10 years in some cases.
The cost of laying the vertical/horizontal pipes is the big kicker in cost.
A friend has had the dickens of a time trying to get a quote on that.

I look at these systems as problematic. They run virtually 24x7 in the winter;
both for efficiency. So power outages present a problem. You'll never run one
from a PV array. But as others have pointed out - it's still a cheaper option
than putting up a PV array or doing other efficiency changes (windows, wall
insulation upgrades). It's an attractive option for those who only have
electricity and are in need of a new furnace.

For a co-housing project; I'm wondering about it. The snag is sizing. Some of
us are willing to live with 16 to 20C daytime temperatures in homes; but many
are not. Others like their home at 24 or 25C and so what do you assume?

The joke on me is now that I've upgraded to a high-efficiency gas furnace; the
furnace is nearly 1/2 of my total electrical use (high-eff furances are pigs)
and the gas connection fee is around 1/4 of our total gas bill! I'd seriously
consider only having a gas or electrical connection because of the connection
fees. But not many are willing to live the lifestyle necessary for going off-grid.

...the gas connection fee is around 1/4 of our total gas bill...

Aye, that's the part about trying to conserve that gets to me too.

Our city says we need to conserve water, so they hike the sewer and connection fees.

Here's the numbers from my last water bill ( Southern California ):
Service Capacity Charge: $16.33
Water Consumption Charge: $1.64

Yes, I pay ten times as much to get access to city water as I do for the water I actually USE. I am in a rather dense neighborhood nearly in an older area of town. The well the city pumps the water from is about three blocks away.

I get the idea they charge access fees is so that the people who use little of a resource get nailed with the same increase as people who use a lot. Don't charge by how much you use, instead nail someone for mere access to get to any of it.

Its a marketing plan to subsidize quantity users. The single individual pays just as much for TV cable as a huge family with all their friends.

Same thing with this damm "per mile" road tax I keep hearing of, where a NANO would be assessed just as much tax as a HUMMER. When will it stop? Will the rich have Congress pass a "heater" or "air conditioner" fee on the poor so one can heat or cool a mansion for the same cost as a small apartment room?

The rich have the ear of the lawmaker. The poor don't organize and vote. So the rich plan ways to force the poor to pay, and has the government enforce the plan.

side note:

Personally, I would have loved to have seen a "music piracy revolt" in the wake of the Supreme Court decision on the Kelo vs. New London eminent domain case. The Supreme Court of this land seemed to find no problem with one group of people taking another's property. I would have found it most interesting to see "distinguished learned men in Robes" try to show where taking and evicting Kelo from her property was OK, but sharing a song was not. Show them juxtaposed with their placing their hands over their hearts and exchanging their allegiance to the flag with justice for all.

Especially if the people were worked up enough over it that they were gonna impeach any politician which signed the DMCA.

It would have been interesting to see the big money of the recording industry go up against the big money of the real estate development team that wanted Kelo's house.

"They run virtually 24x7 in the winter."

If your GSHP is undersized (and thus relies on backup heat for the very cold days), then it will run longer since it may run close to its energy transfer limit. Our unit was oversized for an eventual house expansion project. For a typical winter day (high of freezing and a low in the low 20s F), it hardly runs at all. For a cold day (high around zero F), it runs more than half the time.

I should say that as we continue to improve the insulation material in our walls (it is an older house that still has some unimproved insulation in the walls), the unit will more easily heat the house.


So that, for example, if I were using this as a heating system, with the heat generating part inside the house, and the air outside providing the cooling part of the cycle, as the temperature outside drops, so the system becomes less efficient.

This is somewhat mixed up, or perhaps just poorly worded.

You are not generating any heat, except that due to inefficiencies of the compressor etc. When you are heating your house, the air or ground is the heat source and provides the warming part of the cycle (heat flows into the circulating fluid). By later compressing the fluid, you force that heat (eventually) into your house. Subsequent expansion of the fluid cools it so it can absorb heat again. Everything is reversed when you use it for AC.

Heat pumps are hardly new, during my childhood in the 1950;s a neighbor installed a heat pump. I was impressed when my father describe how a heat pump worked, so I asked him why we did not get one. He explained that heat pumps used electricity which was more expensive than natural gas for heating. The relative costs were his deciding point. He, by the way, waited a long time, before he installed an AC system in his house.

GSHP technology has come a long way since then. Far more effcient. Now the unit itself is smaller than a NG or oil furnace. They can also be run in stages to conserve power, low setting in the spring and fall, highest only on the real cold days. All automated.

Puzzled by that. Surely a gas central heating needs an electric pump to circulate the water. What is the difference?

I believe that the natural; gas was used to heat manure produced by various posters on Oil Drum. The pump would have been for spreading deodorant.

the Actress* woke me the other day with an appropriate track from the Beatles Sgt. Pepper’s Lonely Hearts Club Band album, suggesting that our remaining tenure at this place may be a little time challenged.

Should we be wishing you a happy 64th birthday, then? :-)


64 would be tardy.

In general, you should take care of your building envelope (insulation, air sealing) before installing a new heating system. A good building envelope reduces your heating bills right away, and then you can design your new system based on the reduced heating load.

A GSHP makes the most sense for homeowners who already have electric heat, because the increased efficiency of a GSHP over electric resistance heating or an air-source heat pump will translate directly into money savings. For someone like me with natural gas heat, a big chunk of the increase in efficiency of a GSHP would be offset by the much higher price of electricity than gas per unit of energy. Furthermore, my electricity (New England) is highly dependent on natural gas in both availability and price, so price fluctuations for each will most likely be closely matched. Finally, I suspect that in the case of outright shortages, the authorities would most likely cut residential electricity before cutting residential gas due to the problems with relighting pilot lights in residential combustion appliances. And this is after first cutting both electricity and gas to businesses.

Regarding thermal vs. PV solar, there is an interesting thread over at's The Wall blog: Zero Energy Case Study Report.

We had a geothermal (ground source) heat pump installed in our house in November 2006, to replace a 32-year-old oil furnace/central AC. We live in the Washington, D.C. suburbs (Montgomery County, Maryland). The installed cost was high, but we're very pleased with it; my estimate is that it is currently saving us around $2000-2500 in heating / cooling / hot-water costs a year.

It is a Waterfurnace 4-ton unit, the Envision model, which was introduced about two years ago. The ground loop is a vertical closed system, in a single 600-foot-deep well, and uses Environol (95 percent ethanol solution) as the thermal-transfer fluid. The loop itself is a high-strengh black polyethylene tubing; there is a 50-year warranty on it.

The installed cost was around $28,000. About half of that was for the well drilling company, who did the complete installation of the ground loop, up to and including extending the loop into the house, flushing and filling it, pressurizing the loop and connecting it to the geo unit.

Between the federal and state tax credits, and a Maryland ground-source heat pump assistance program, the total rebates amounted to about $1600.

The cost did seem high to us at the time, but we had another estimate that was not much different. We knew someone who lives in a rural area in Maryland, who had a geo system installed in 2000 for $15K -- but energy costs were a lot lower then than now, and in the D.C. area, everything is more expensive...

We also have desuperheating, or hot-water generation -- the DHW (domestic hot water) pump in the geo unit circulates water between a built-in heat exchanger and the hot-water tank. Desuperheating is a big factor in energy savings with ground-source systems. During cooling season (it gets hot and humid here in the summer), water heating is free -- the heat that the heat pump would ordinarily eject out of the house goes into the hot-water tank. During heating season, when the thermostat kicks the system on, the heat pump heats the water, but using much less energy than electric resistance heat.

Apart from changing filters, there is not much maintenance involved. There is no issue of rust outside, because the only part of the system that is exposed to the elements is the polyethylene pipe where it comes up out of the ground and into the house through the exterior wall. Other than a standard six-month technician check-up, the only thing that may need to be done is to add a bit of fluid to the ground loop, which tends to expand slightly during the first year or so of use. The heat pump unit will probably last 20-25 years. Our installer recommended a closed-loop system -- open-loop (well-water)systems don't last as long, though they are less expensive to install, and closed-loop systems are more of a sure thing -- one isn't dependent on the groundwater as the thermal-exchange medium.

A ground-source system seemed to us to be best for our situation. It gets cold in the winter and hot in the summer here; we don't have natural gas; and we realized we were looking at $700-800 (and rising) oil-tank fillups 3-5 times during winter.


I'm considering a ground source system, but I'm curious about electricity consumption of the unit. Since you have had your system installed for more than a year, do you have an estimate of how much your yearly KWh consumption increased after you installed the unit?

Our current consumption is about 17 KWh/day averaged over a year, which I think is decent considering both my wife and I work from home and have two kids. We currently heat our house with one of the newest clean burning wood stoves, and I harvest the wood myself, so I know that our costs would increase with a heat pump, but labour would decrease.

We live close to a lake in Southern Ontario and the water table is only about 5 feet below ground level in sandy soil, so I know that the ground loop would be less costly than average.

If you're interested I can get the guy to visit you, he's in Strathroy. He has all that info on the cost/benefits relating to various other modes of heating. The savings range from 50% to 70% total costs to heat and cool. And we get $9,000 in government rebate grants, and they have arranged low cost financing with one of the banks (but increases your payback time).


I'm looking at my most recent 8 months' worth of electric bills, which each show usage for the previous 12-month period. Our usage for 2007 averaged 49kWh/day (@ 10.89c a kWh, that's $5.33). We have a 3100-square-foot 2-floor wood-frame house built in 1974, all-electric, insulated (though there are a few spots I need to attend to). As I recall, our electric usage during the winter months of 2007 (Jan.-March), after we installed the geo system, was roughly double that of Jan.-Mar 2006, but our usage during the summer months of 2007 (June-Sept.) was only about half that of the same months of 2006. Our biggest electric bill during this period was February 2007, when we had a three-week cold snap, with a bill of about $350, of which I estimate half ($175) was usage by the geo system. But, if we had still had the oil furnace, our heating bill would have 3-4 times that...

Thanks for this info. Much appreciated.

This is great to know from someone who has a unit we are getting. Thanks, feels good we made the right choice. Though our government grands area bit better than yours .


Good luck with the installation. You're right, recovery time for the fluid in the ground loop is key to an efficient system. After inserting the ground loop tubing in the well, our well driller backfilled the hole with bentonite clay grout, which helps improve the thermal conductivity of the soil, as well as to keep rainwater from infiltrating the groundwater supply.

Yes, appearently, according to the watertfurnace guy who was here, that back fill with clay is a law requirement for such bore holes, regardless of use. But it does give a direct contact from the piping to the ground.

We had a geothermal (ground source) heat pump installed in our house in November 2006, to replace a 32-year-old oil furnace/central AC. We live in the Washington, D.C. suburbs (Montgomery County, Maryland). The installed cost was high, but we're very pleased with it; my estimate is that it is currently saving us around $2000-2500 in heating / cooling / hot-water costs a year.

It is a Waterfurnace 4-ton unit, the Envision model, which was introduced about two years ago. The ground loop is a vertical closed system, in a single 600-foot-deep well, and uses Environol (95 percent ethanol solution) as the thermal-transfer fluid. The loop itself is a high-strengh black polyethylene tubing; there is a 50-year warranty on it.

The installed cost was around $28,000. About half of that was for the well drilling company, who did the complete installation of the ground loop, up to and including extending the loop into the house, flushing and filling it, pressurizing the loop and connecting it to the geo unit.

Interesting. I have a 1500sf house in Wilmington, DE. My climate is very similar to MontCo, MD. I've spoken to 3 different companies about a geo system. They're all talking about a 3 ton system, total cost ~$22K. I'm curious about the 1 foot of bore hole recommendation for every s.f. of house. All three companies have said a single 450ft. hole would do it for this application. My well pump is set at 90ft., so I'd bet the water table is around 60ft. Does the height of the water table greatly affect the amount of bore needed? I'd do a closed loop, since the water here has a high mineral content and is acidic.
I need to replace my system anyway. I'd be looking at $10K-$12K for a new conventional gas furnace or air source heat pump and a tankless unit for water heating.
I'm leaning toward a geo system because my family can't seem to leave the thermostat alone and put on a sweater. They're hot water junkies, too. Grrrr. If I'm going to spend the money, I might as well make it something that's cheaper in the long run.

If you can hang on then you might want to go for one of the carbon dioxide air heat pumps - not sure when they will hit the States, but they are due to come to Europe soon.

They are much more efficient than other types, and should give ground source a run for it's money, whilst being lots cheaper, although that is not quite fair as presumably a ground-source carbon dioxide type would do better yet.

They operate down to -20 too.

Here's some info:
"Eco Cute" CO2 Heat Pump Water Heaters

Due to the acidic high mineral water, an open loop MIGHT be a bad idea. How much treatment do you need to drink the water?
If you are going with a closed loop, with a 3 ton system, then the recommendation should be 3 500' boreholes. However, these will not require casing, the process is drill, place the tubing, and grout. And don't let them sell you that thermo conductive grout. The "conductivity" is minimally improved and is NOT WORTH THE INVESTMENT!!! Normal grout is plenty sufficient.
Also, the water table has some effect on "required" length, but the basic lesson is, for a small residential system, it is not worth the risk of shortening your boreholes on the front end. You might get down to 400' each, but then at the end of the heating system you will be sacrificing efficiency.
Good luck, and it is the way to go. If you want to calculate payback, go to
This is a useful calculator.

If by chance, you can go with an open loop, than one 300' 6" cased well hole will suffice. With water at 60' that gives you 240' of water column, sufficient for a standing column well system. See my comments above.
Any questions...


I live in Michigan and we installed 4 wells at 150 deep each for 4 tons of heating (which provides more than 4 tons for cooling). Thus, your 3 x 500 foot boreholes seems very high. Is that for northern Cananda or some other country above the artice circle?


I don't know enough to say if the height of the water table affects the amount of bore needed, but the depth of the hole compared with the square footage of your house fairly closely corresponds with ours. I understand that the underground temperature does increase as one gets into the warmer latitudes, so maybe a smaller ground loop is needed in our mid-Atlantic region. If you want any further information, you might contact our installer -- Dynatemp in Silver Spring, Maryland; the head of the firm is Tom Hackshaw.

I have had a heat pump for 4 years. I have used approx. 370 dollar worth of electricty this year to heat my home in mid Michigan. If you install a unit have your installer put a kilowatt meter on the units electrical feed. My installer said too may people blame high energy consumption on the heat pump, they may be using large amounts of electricty in other ways. I have an insulated concrete form basement with 2x6 inch wall with blowin in cellouse insulation ,house wrap with insulated siding. The point is, build a soundly insulated house then put a heat pump in. It's a great unit I'd buy on in a minute. The upfront costs are high but pay off time seemed reasonable. Also on other point if your using new constuction don't use fiberglass insulation. Fiberglass is a poor insulating material.

We considered a ground sourced heat pump when we built our house in NJ in 1995. The house is well insulated (4" polyisocyanurate) on all sides - including the basement walls and under the basement concrete slab. The primary heat source is passive solar with the concrete slab acting as heat storage. The passive solar heating system really ends up costing a fraction of a conventional heating system due to it's simplicity. But back to the topic... Our choice was between heat pump at $15k using horizontal PEX tubing in the ground or a $500 electric resistance heating element installed into the solar air handler. We chose the $500 solution primarily because our bank account was $0 and we do not believe in borrowing money. It was a good choice. The electric heat has cost us between $400 and $500 per winter for the last 12 years.
As it turned out the payback period for the heat pump was more than the expected life of the heat pump system.
So I'd have to agree that paying a bit more for a well insulated house is the best way to go.
Since then we've added a tracking 10KW PV system and a solar hot water system using evacuated glass tubes. With the PV system our energy costs have gone down to about $74 per year and now with the very recent hot water system I don't think we'll ever pay for energy again. The PV system will be paid off next year and the hot water system has got many years to go.
Now, if I could just get or build an electric car with minimum 100 mile range....

Passive solar heating is fine when you are located where the sun shines a lot. Not here in Southern Ontario. So far this year the sun has been out during the day less than 20% of the time. Plus only daylight from 7am to 6pm. This makes it difficult to heat a house with the sun when it's cloudy for weeks at a time.

We live in Southern Ontario as well, and went with a combination of an air-source heat pump and a significant insulation upgrade when we retrofitted our house this year.

I would not dismiss current air-source technology, as it has also improved considerably over the past couple of decades. So far this year our whole upgraded heating system (heat pump and insulation) has been cost-competitive with gas in terms of our monthly bills, even in an unusually 'normal' winter, unlike the 'global warming specials' the region has had lately.

Air-source efficiencies vs. electric resistance heating I have seen quoted are in the 150-300% range, as compared to the 500% and higher range of efficiency for ground source, but the lower capital cost is a factor for some of us.

All of us peak-oilers in Ontario are very aware that the natural gas supply here, which I believe heats almost 90% of the residences where I live, is likely to be in trouble in as little as a year or two, so alternatives are top of mind.

In our case we also went for redundancy, with a good-quality catalytic wood stove and a good supply of seasoned wood as an emergency backup.

An order of priority that makes sense in Southern Ontario if your goal is a resilient energy-descent system might be:

- Insulation and air-sealing (Lots of it! and more!)
- Non-gas heating system (G/S or A/S heat pump, electric resistance, even oil in a pinch)
- Off-grid backup heat (wood stove, solar thermal, large furry animals, etc.)

A 'anti-greenhouse-gas' or 'strict-peak-oil' approach would be similar, but avoid fossil fuel options altogether.

Wow, 10 kW of PV on a residence? That is a lot of power. When I do PV systems for customers I mandate conservation and efficiency upgrades be done before any active RE is installed. Since sustainability is the real issue, I feel installing gigantic RE system to compensate for waste and unconscious consumption is more of the brain dead thinking that has us facing the mess we are.

We have a Mitsubishi, 3 zone, air sourced heat pump (COP of 3.08 @ 40 F) and are zero energy with only 4.5 kW of PV. I think it is really great to heat three separate interior zones with one outside unit. Our annual average daily consumption is 15 kWh (included heating), which the solar electric system easily takes care of.

I installed a SDHW system years ago using two 4 X 10, black chrome flat plate collectors, which, unless you are heating water above 160 F, are actually equal or more efficient than the over hyped, high tech glass panels you had installed.

I wish Mitsubishi made a ground sourced multiple zone heat pump but they do not. But our climate rarely gets below 25 degrees F so an air sourced unit works very well here. A modification I have considered is to put a ground source fed heat exchanger in series with the air intake on the unit we have.

Currently in our area resistance electric is cheaper/BTU than oil, kerosene or propane heat. Our heat pump is approximately 1/3 the cost of oil. As non-renewable fuels continue to increase in price, more people will switch to electric for household heating. This will place increased loads on the electrical grid, and I wonder how this will effect its stability.


That sounds an excellent system you have chosen - I don't know where you live but I wonder if you would care to comment on how well your flat plate collectors do in cloudy weather?

Wintertimes in the UK are seriously overcast, and it is very important.

Also, my brother has a 1920's vintage semi house, and the installation of underfloor heating would be impractical there.

If you assume the same rate of power use, but having said that his house is British and so small by American standards and very well insulated, what rating of PV panels would he need for a system with oversized radiators but not underfloor?

My understanding is that you should get about a COP of 2.5 with that.

I realise that it is impossible to be definitive, but what would be your guess?


I totally agree with your method RB. Reduce the energy your needs by reducing the energy that your home wastes. Reduce the heat loss with super high levels of insulation and in the end any house can be heated with a very, very small energy input.

Only after hammering down the energy to a bare minimum should you add the renewable energy system.

When did you install your 10kW PV system, RB?

While I agree with that in theory, in reality I'm lighting both ends of that candle to whatever degree that I can. (Increasing Efficiency while also investing in Alternatives) To me, it's just the same as increasing your income as well as curbing your expenses, and any move you can make in either direction is probably worth doing.

I've been replacing windows and filling leaks and underinsulated walls, etc.. but also have been buying a PV panel at a time when I've had the cash, and making other sources myself where I can.


I recently assessed the various insulation materials available and learned that polyiso (or polyisocyanurate) is the most efficient insulating material generally available. I was just renovating our laundry/utility room and cut sheets into sufficiently small pieces to fit between the studs of our 2x4 wall, and several pieces resulted in either 3 or 3 1/2 inches of insulating material. After reinstalling the drywall, I did a simple test of the insulating quality.

With the recent cold spell, the outside temperature was around zero farenhaut. If I place my hand on a segment of the wall our house insulated by fiberglass, the wall felt slightly cool to the touch (but not cold). When I touch the segment of the wall which contains the newly insulateld polyiso, the wall felt like room temperature. This suggest that there is very little heat loss to the outside. I estimate that the wall is R-22 or potentially even higher, which is impressive for a 2x4 wall.


If you have an in-line meter for the system, could you tell me what your Kwh consumption is for a 1 yr period? Do you also cool with the system in the summer?

We used 18k KWH per year before the PV system was installed November 2004. Now we are using about 16k KWH and hopefully will get that down closer to 10k KWH. We do use A/C a little in the summer. The hot air system can be run in 'reverse' to cool the house but that does not take out humidity. Some of you are saying what a pig I am for using such a large amount of energy and installing a big PV system. But remember we designed and built this house in the early to mid 1990's. Do you know how tough it was to get people to design and then build a very well insulated house w/passive solar heat? It was next to impossible. Architects, builders, carpenters, HVAC contractors, etc. were all telling us we were nuts and would not even consider working for us. Oil was cheap. We ended up doing at least 50% of the work ourselves. We did the best we could on a low budget using no financing.
I've done what ever I can to save energy. I designed and built a variable speed controller for the blower that runs the solar hot air system. That saved 1.9k KWH per year. Next was the hot water heater - replaced with solar hot water. Expected savings will be about 5k KWH per year. Next is the fridge. I bought a Kill-a-watt meter and will hook it up to the fridge. All lighting is compact fluorescent. The house is 2700 sq ft.
The PV system was sized for our current needs in 2004. But I also sized it this way knowing that the PV panels lose about 1% efficiency per year so I will be forced to reduce consumption by 20% over the 20 year lifespan of the system. And besides, how could anyone turn down a 70% rebate from the state? If I had waited to do efficiency upgrades like Todd suggests then I would have missed on the state's great rebate. The rebate was lowered a few weeks after we installed and then lowered several times until now there is no rebate. The state will be implementing a different scheme soon for incentives.


I am a bit confused by your units. My goal is to use less than 3,000 kWh in 2008, and I am pretty efficient.

Are your numbers 18 kWh per day and not per year ?

Thanks for Clarification,


For a moment I was confused also until I noticed that he had typed "18k" as in 18,000 kWh for the year.

I'm sorry Shastatodd chose to speak to you like that. I hope he can see how condescending he was being. Sounds like you've worked hard and built a good home. Maybe you'll end up in surplus and will be able to sell power to neighbors or the grid someday. Either way, I don't think you can go wrong owning a bunch of PV and Water Heating eq. I have to imagine that PV will hang onto its resale value really well from now on, as well.


Ho Ho Ho, so what did The Actress say to The Bishop?

Tell me, will a GSHP provide sufficient heat to heat a house and hot water in Aberdeen in Winter? I gotta swap out our Medieval gas boiler some time and so wonder if a GSHP is an option. How hot does the hot water get? This would then free up the flue pipe where the boiler currently sits for a WBS (wood burning stove) and we could all live happily ever after.

I got about 70 m2 grass out the back.

One argument is totally missing.

Heat pumps use carbon free energy!

This is very important for the carbon restricted economy.

When oil, gas and coal are depleted, then we have biomass left. But biomass can only replace those energies partially. While there is enough renewable energy in electrical form (solar thermal, PV, wind).

So, then you have to choose where to use the biomass. Take the following choices:
- Using biomass to convert to some carbon fuel to use in a plane and use a heat pump for heating your home.
- Or, use biomass for heating your home and use the electricity to fly a plane. huh???

You see!

If you look to 100% sustainable energy supply, than the heat pump is very important technology.

That is why we must start with thinking in a 100% renewable world, and go back to 80%, 60%, 40% and 20%.

I you crawl to 20%, you might have made bad choice for going to the 40%.


Closed loop ground source heat pumps are a very good idea for new installations.
These installation reduce GHG emissions considerably.

They require little maintenance and units last +25 years(much longer than house furnaces, condeners).
The piping is 1-1/2" HDPE gas piping and
They have a COP of almost 3 in heating and also provide dirt cheap AC in summer.

It's comparable with running a
high efficiency gas condensing furnaces as far as your electric bill goes. The system can also provide domestic hot water as well as heating and cooling.

When gas goes to $2 a therm I might put a ground source heat pump in ( or if the government decides to give me a subsidy).

Vertical boreholes are very expensive $2000 for a sigle 1 ton 250'deep borehole. The boreholds need a special heat transfer grout.

Horizontal slinky piping in 6' trenches is cheaper $1500 per ton but require lots of land, 4 times as much as boreholes.

SWF My total energy comsumption last year was 7092 kw/hours at 9.2 cents per kilowatt comes to $652.This also includes air conditioning and approx one half of my hot water heating cost are provided by my heat pump. If you are contimplating a heat pump make sure you insulate. Any heat system can be made to look good with an adequate insulated house. This by the way is in mid Michigan. Air condition costs are extremely low with our heat pump.

Air Supply or Water Supply Heat Pump ?

I have become aware of a significant difference between EU & USA ground source heat pumps.

In the EU, the typical ground source heat pump heats up water which is then circulated through the house.

In the USA, the typical ground source heat pump heats up air which is then circulated around the house.

The EU system cannot be used for summer cooling because of condensation problems (except in the driest climates), while the USA system can (and provide humidity control as well).

The operating temperature of the heated water system tends to be lower than the heated air, which improves efficiency.

Wells or horizontal pipes are the most expensive component and can be used for either. I am wondering if a USA system might use an air supply system for summer cooling and a winter water supply system for winter heating (with the air supply system as a back-up, for coldest days) ?

Also, ground water in New Orleans is between 70 & 72 F (22.2 C & 21.1 C) and great economies of heating. With proper insulation, VERY little heating is required. (Below 0 C twice this winter so far). 25 C on Mardi Gras Day :-) 60 F, 15.5 C right now at 5:30 PM, february 7th.

OTOH, cooling and humidity control are important.

I checked ten years ago and ground source air cooling, with water pumping losses, was no more efficient than air source in New Orleans (our high humidity increases the heat transfer & specific heat of air above ARI handbook values).

Just added info,


GSHPumps are great systems, but I would not suggest to anyone to install one until they have first pursued home energy reductions in a big way. Here’s why.

Three years ago some friends and I decided that we would see if we could reduce the amount of energy that each of our homes use by 90%. At the time we were motivated by global warming and the ever increasing energy rates. It’s only been the last couple of months that we have been getting up to speed on the significance of peak oil.

Anyways, when we first started discussing possible plans of attack we talked at great length about the pros and cons of various types of home heating systems. In the end we decided that changing our existing heating systems would be one of the absolute last things that we would pursue. We recognized that we had absolutely no control over the future price of any fuel or even the price of electricity from the utility. As we have learned more about peak oil we recognized that we also have no control over the future availability of any fuel. Even the local availability of cord wood could become a problem as energy resources become tighter and tighter. The only real control that we have in each of our homes is the amount of energy that we use each day which is directly linked to the amount of energy our homes currently waste each day.

We started working on our home energy improvements three years ago. As of this year we have achieved heating reductions of 28-35% for each of our homes, both space heating and DHW. We are able to do all of the work ourselves which obviously keeps the cost of the improvements low. The basic improvements we have completed to date are: super insulating the attic, insulating the floor headers in the basement, insulating basement walls, installation of drain water heat recovery, eliminating air leakage, timer switches for the heat recovery ventilator so that it only ventilates when people are at home and limits the amount of time it runs during the coldest hours of the day. Some of the improvements that we have on our “to do” list are: additional insulation for the foundation, super insulating the exterior walls, up-grading to higher efficiency HRV units, installing solar water heaters and up-grading windows to triple or quad glaze.

Although drain water heat recovery has been available in our area for a few years I know that most people are unfamiliar with it. Here is a link for anyone wanting to learn more:

I’m sure that some readers here will think that making a home so energy efficient that is does not require any type of conventional heating system cannot be done. Maybe they are right, but we have racked up a 30% reduction in the energy we use for space and water heating thus far and we have yet to super insulate our walls and foundations as well as install up-graded windows. I’m confident that within about 3 more years that we’ll be reaching our goal.

In reference to your window plans,

Have you considered putting insulated Shutters outside your windows? I don't know if there are downsides with frost, fogging, etc.. and my plans to do ours would involve devising a Handle or Crank that actually penetrates the Wall or Window Casement to operate the things (Maybe a motor?), so they'll be easy to do every night.

Currently, we have insulated Window quilts on basically all windows in the house, and always keep them shut at night, but I keep thinking that shutters made from 'Tuff-R' or some similar PolyIsoCyanurate Foam Board (and dressed nicely with wood) would be the more effective and obvious route. Making a tight seal to the windowframe would be another issue, but surely not insurmountable.

Bob Fiske

I have been doing a lot of fact finding about options for up-grading windows. Moveable insulated panels on the exterior is very challanging in our climate with the ice and snow in Eastern Canada.

Any of the off-the-shelf insulated blinds or other solutions are extremely expensive given the energy savings and honestly don't meet my needs on the performance side. The typically only deliver an extra R2 to R4. The reduction in heat loss that these offer is simply too low for my needs.

I'm planning to build my own insulated panels. I'm aiming for a panel that has about R20-R30.

We would be interested in seeing the fruits of your labors.

Agree with your opinion of commercially available off-the-shelf insulated blinds. Expensive decor, thermally feeble.

I installed triple-glazed double low e nitrogen filled windows that range from U = .26 btuh/deg F ft^2 (fixed pane) to .33 (sliding doors). Couldn't get argon/krypton fill, vendor (HD) said the seals would blow during transport over the pass to my location. Also have three double pane skylights installed by home's previous owner. I've started using 2" thick expanded polystyrene boards ("R-Tech") fitted into the inside of window & skylight openings like corks.

I'm getting most "mileage" from corks in skylights, since the wells from dropped ceiling to roof weren't insulated when previous owner installed them (duh!). Cork at ceiling level insulates both well and skylight. For my area (Bend, OR, USA) payback pencils out to about 1 yr. Am also measuring the effective delta UA, stay tuned...

Convenience-wise, I am leaving skylight corks in 24/7 til spring. Also 1 of three windows (my office). But my wife insists that two other windows get uncorked every morning...

Let me know if you figure out how to conveniently stow R-20 or R-30 panels when not deployed.

I'm satisfied with my solution thermally, but shudder to think what would happen in a fire - polystyrene smoke is awful stuff. Any ideas about what's best in a fire??

Next project: Install R-25 underfloor insulation and passive cooling by-pass in what used to be a "conditioned crawlspace" (duh ^2).


Some years ago I was in the electricity industry and heavily involved in the promotion of heat pumps. We had a very fancy device for testing heat pumps (forgotten its name but it came from Sweden). I tested a number of Water Furnace GSHP's in various cold areas in Australia during winter. The performance was impressive with Coefficient of Performance ranging from 3.5 to 6. As others have said the killer is the installation costs particularly the bore holes.
Since then the performance of air source heat pumps has been getting better. Even in the 90's I tested a Hitachi variable speed unit one morning at -5 deg C at it was still giving a COP of 2. Of course the outside coil froze up and the unit went into defrost - it sounded like a 747 as it ramped up to full speed. As a result the defrost was over in about a minute and the inside temperature was unaffected.
So my conclusion, if you are in an area subject to snow and/or extensive cold weather >10 deg C below freezing then consider a GSHP otherwise go for a good quality Air Source HP (the Japanese brands are generally the best - sorry to US readers).

Air source heat pumps are becoming increasingly popular in Japan as water heaters. They are sold by a number of companies under the generic brand of "Eco-Cute". The "Cute" is a pun on "kyuto", the Japanese word for supplying hot water. All the system run on low-tariff overnight power. Japan's electricity is something like 40% nuclear, so there's plenty of it at night time. At present a lot of it pumps water uphill. Most Eco Cute systems heat up a 350 or 460L tank. CO2 is used as the refrigerant to heat the tank to 90C.

Air source pumps that are good to -15C (Japanese "kanreichi shiyo" or "cold region spec") are also on sale, though the COP will take a big hit.

This link suggests Eco Cute systems will be on sale in Europe soon.

(GSHP) Ground source heat pumps .I am looking to build a new house soon and have some experience with them . They do work well either vertical or horizontal. and give A COP of 4 or better. But from a Green point of view point less they are pointles sunless they ar powered from renewable for the following reason. Grid generated electricty has an effeicency of 35_40% normaly. so your GSHP is effectively only recovering these losses . Most new Condensing Gas/Oil boilers have an effiecency of 90%. You are also dependant on the Grid for power. To my knowledge the German goverment has stoped grant aiding them for these reasons.Heat recovery ventalation ( Using Heat pump see no connection) and condensing boiler or high effiency wood stove with good insulation is the best option long term. Also Vacuum solar tube if done right can supply all domestic hot water even at reasonably high latitudes.

Nobody answered the question, what is the difference in electricity consumption between a heat pump and a gas or oil fired heating system?

Your question can't be answered, after a fashion.
We have a gas furnace and an electric AC, which we use very, very infrequently in the summer despite temperatures in the 90's. We are switching to a GSHP-- no more gas for the furnace, maybe more electricity running the heat pump in the winter. In the summer, we will probably reduce our electricity consumption by 30%, but we will have a much more comfortable house.
In the end, we are substituting renewable electricity in the winter for natural gas, and reducing electricity somewhat in the summer.

I have had a GWHP for 25 years and am completely happy. My pay back time for this installation was about 7 years but since then have been saving about $1000 a year. More in the last three years with rising cost of natural gas. Super insulation is mandatory and the passive solar HW heating and PV helps as well. If you are looking into a new build--consider an enertia house. At

Super insulation is mandatory and the passive solar HW heating and PV helps as well.

I've often hear this said with regards to GSHP installations, but I don't follow the logic. If I dramatically reduce my space heating requirements through better design and construction techniques, improved insulation and air sealing, etc., the difference in the operating costs of a conventional heating system versus a technically superior, but more expensive alternative is minimal. In other words, if I can heat and cool an energy efficient home with an air source heat pump for $600.00 a year or a GSHP system for half that amount, can I reasonably expect to recover these additional costs?

Last year, I spent a little over $600.00 to heat my home with a small ductless heat pump and an oil-fired boiler (3,200 kWh of electricity and approximately 355 litres of heating oil). The installed cost of the heat pump, which now supplies roughly 80 per cent of my total space heating needs, was $2,100.00. Now if someone could explain to me how a GSHP can outperform what I have now, I'd be tickled a dark shade of pink. ;-)


A very small cheap GSHP (say 12,000 or 18,000 BTU) might be economic. Perhaps small enough to use cheaper horizontal trenches in small yard. Or a number of cheap 6 meter deep wells in parallel.

One key is to use it first whenever heat is needed (highest possible capacity factor).

BTW, I kind of like the "three halves approach". Three separate systems each capable of meeting half the demand on coldest day. Any one capable of keeping the pipes from freezing. Mix and match as economics change.

Best Hopes for Energy efficiency,


Hi Alan,

Your "three halves approach" makes a lot of sense. As it turns out, I have four options: 1) the ductless heat pump is my least costly at $0.043 per kWh(e) and the one that supplies roughly 80 per cent of my needs; 2) an oil-fired boiler which helps out on the days when the heat pump can't keep up with the demand -- at $0.889 a litre, it clocks in at $0.101 per kWh(e); 3) in-floor, electric radiant heat which is generally used only in my home office on the coldest days of the year (this room has three exterior walls and a fair amount of glass, and is located on the north side of the house where it is exposed to winds off the Atlantic) -- at $0.1067 per kWh, its operating costs are similar to those of oil; and 4) four propane fireplaces, used only for emergency heat in the event of an extended power cut -- at $1.05 per litre, propane is twice as costly as oil and electric heat and five to six times more costly than the heat pump.

In any event, I don't mean to sound like a cranky pants, but I don't understand the economics of this type of heating; granted, not every purchase need be judged solely on its economic merits, but if funds can be spent elsewhere where they could do more good, it would seem foolish to ignore some of the less costly alternatives if, in fact, they offer superior performance.

I mentioned earlier the space heating requirements of a conventional new home in our climate (~ 8,000 HDD) run in the range of 15,000 kWh/year. At $0.1067 per kWh, the annual heating costs of this home if equipped with electric baseboard heaters is $1,600.00. An air source heat pump with a HSPF of 8.5 would get this down to $640.00/year and a GSHP with a seasonal COP of 4 would further reduce this to $400.00/year. The incremental savings in this case are just $240.00/year and if we were to achieve an additional $250.00 reduction in DHW costs, our combined savings are $500.00/year. If we use this number and assume a 6% escalation in electricity costs and a 5% cash discount rate, the ten-year NPVs are negative if the initial premium exceeds $5,000.00. In other words, if the costs of a geo-exchange heating system are $5,000.00 or more than an equivalent air source heat pump and conventional electric water heater, you might as well have invested your money in Bre-X.


As usual, I'm late to the party here. This was an interesting thread, and it was helpful to see what others have done. Our efforts are detailed at

In Southwest Connecticut, our GSHP experience has been less than stellar, but definitely positive. A few mistakes were made, namely, we didn't get the desuperheater, and the units were oversized. I know that now, and getting those right would have boosted our return. I blame the contractor for some of this, but in the end, I didn't do enough homework beforehand.

The other problem we face is a high electricity cost. At 17+ cents per kwh, our rates are one of the highest in the Continental USA. In the Midwest, a GSHP would be a no-brainer, given the lower power costs (at least for a few years more). The GSHP economics is really a spread between electric cost and heating fuel cost. Here in lower Fairfield County, we get hit on both sides.

The primary reason for installing our system was to reduce our oil dependence, for we had oil heat, and we still use it for backup. Nonetheless, our oil consumption went down dramatically, and our foreign dependence is reduced. If you look at the energy problems the USA faces, I'd rank it as (1) foreign dependence, (2) global peak supply issues, and (3) carbon emission. I'm trying hardest to beat on number (1) while helping with the other 2.

From a systems perspective, we have replaced oil heat with natural gas electric generation (details on the blog), and in the end, I estimate we have reduced our fossil fuel consumption by about 15% from what it was prior. With things in the pipeline, the fossil fuel consumption should go down another 30-50% going forward.

If I were to start today, given that our house is well (but not super) insulated, I'd look towards solar thermal first, see how it performed, then look for the appropriate right-sized supplement.

Hi GoingGreen,

I've come late as well, so let me welcome you aboard.

I know it sounds like I'm bashing GSHPs but that's really not my intent; in colder parts of the country and where DHW demands represent a high percentage of the home's overall energy needs (think teenagers and showers), they're likely to be the preferred option. The key point I wish to make is that they're not the only game in town and that for many of us, a good quality air source heat pump offers much better value. Before anyone installs a GSHP, they should look carefully at the numbers and determine if the premium they would pay would be better spent on additional insulation and air sealing. Generally speaking, dollar for dollar, you earn far greater returns from reducing demand than you do by substituting another fuel source. And, again, once you reduce your space heating demands to the point where some of the conventional solutions are more cost competitive, the economics of a GSHP become, shall we say, problematic.


"The GSHP is one of the most efficient residential heating and cooling systems available today, with heating efficiencies 50 to 70% higher than other heating systems"

Ground-source heat pumps are a lot more efficient than that. Natural gas systems approach 100% efficiency (the best being around 95% efficient), while my ground-source heat pump is on the order of 400% efficient. Thus, it is 4 times more energy efficient.

The lifecycle efficiency (and impact on CO2 emissions) depends on the technology used to generate the electricity. However, as we move forward, more and more of our electricity will be produced by renewable means, and should be more efficient than if was produced by combusting fossil fuels.