Currys To Stock Photovoltaics

Currys, a leading high street electrical retailer have announced they are to start stocking photovoltaics. I sign of the times? I think so although I expect the move is as much a publicity stunt, jumping on the `green' bandwagon as a viable stand alone product.

The announcement is covered in this Guardian article.

They say it will cost the average three bedroom household about £9,000 to buy and install solar panels - compared to £16,000 in specialist stores. There are also grants available through the Low Carbon Buildings Programme.

Customers opting for solar power can expect to reduce their energy bill by up to 50% and could reduce carbon dioxide emissions by up to two tons per year. In addition, up to half of the cost of the panels can be offset by an increase in property value, Currys said.

Curious they make the point that half the cost can be offset by increased property value. Isn't this just like saying you'll be able to sell them to the person you sell your house to for half the price you paid for them? That's not my only concern with this announcement though.
The Financial Times also ran the story here (may be behind the pay wall now).
The prices may be more than most consumers expect to spend in a Currys store but reflect a sharp fall in the cost of solar systems in recent years. Panels have come down in price by more than half in the past five years amid intense competition among global manufacturers.

UK industry estimates for further price falls are 5 per cent a year, but global prices could drop more quickly, in line with a wider slide in the cost of electrical goods such as flat-panel televisions.

So panels have halved in price in the past five years? That's not what SolarBuzz are seeing:

Source: Solarbuzz

Their All Solar Module Retail Price Index tracks 90 companies and close to 2000 products, it shows no such decline over the last five years. In fact since the photovoltaic industry overtook the computer industry as the largest user of Si the price has been trending upwards.

The module cost represents around 50 - 60% of the total installed cost of a Solar Energy System. Therefore the solar module price is the key element in the total price of an installed solar system. All prices are exclusive of sales taxes, which depending on the country or region can add 8-20% to the prices, with generally highest sales tax rates in Europe.

I am also wary of the economic comparison to consumer electronics, will the photovoltaic market really respond as the flat-panel television market has? I expect the cost structure is very different.

The Guardian article also writes:

Industry analysts predict £750m in sales in 2010 from a "standing start" now.

The panels are manufactured by Sharp UK, which has a factory in Wrexham, north Wales. Sharp has a 26% share of the solar panels market.

If the price remains at £9,000 that's 83,000 systems. If some price reductions do materialise maybe 100,000. Of the approximately 20 million houses that's 0.5% per year, pretty impressive.

On the Wrexham plant, we discussed this last time photovoltaics came up and it looks like they don't do any manufacturing there, only assembly of the panels from cells manufactured in Japan.

A positive development, certainly but I'm not sure the details we've been given really add up.

Isn't this just like saying you'll be able to sell them to the person you sell your house to for half the price you paid for them?


I think it's more that the economic value of solar is about half of what you pay for it. That is determined by how much you save on your bill and how much value you place on being 'green', compared to the Jones'. The increase in property value would only represent that value, not what you originally paid for it.

Yes, but that is true of everything.  I don't live in the UK, so I don't know how common it is for houses to have pools there, but here in California it is quite common.  You'd think that a pool would add to the value of a house, but if someone doesn't want a pool they might actually ask for a price reduction because they don't want it (although probably only in a buyer's market would you see much of that).  Home values are always about what accessories you add are worth to other people, and it's almost never full price, even if it's something they want.  
There is a long and interesting talk given by Dr. Richard Swanson, President and CTO of SunPower Corporation, the makers of the most efficient silicon panels available for domestic use (220W from a 1.24m²) given to a Palo Alto Research Center (PARC) forum in April this year entitled "Solar PV: The Path From Niche to Mainstream Supplier of Clean Energy". In it he explains that believes that the industry is on the way to 1$/W in 2012 and that the reason that there is a increase in the price over the last year or so is that the manufacturers of purified polycrystalline silicon (polysilicon) the raw material for single crystal growing would not take seriously the photovoltaic industries forecasts of growth and there is a consequent shortage.

 In the early days the photovoltaic industry used the cast offs from the microelectronics industry. Photovoltaic  cells can tolerate lower purity and greater crystal defect densities than microelectronics. He said that he and the other photovoltaic manufacturers were treated as some form of aging hippies with wild ideas when they told the polysilicon manufacturers that they needed to increase capacity. Last year the world produced 1.6GW rated capacity of photovoltaic modules (more than half going to Germany)and in doing so used a greater area of silicon than the microelectronic industry. Because photovoltaic cells are thinner than electronic chips they used less weight of silicon. This year production will be at least 1.8GW and will overtake microelectronics on a weight of silicon used. The photovoltaic plant being built and planned ensure that photovoltaics will soon greatly outstrip microelectronics in  polysilicon usage.

The good news is that the polysilicon suppliers have finally accepted this and are building three massive new polysilicon  plants and Dr Swanson predicts that photovoltaic prices will resume their downward slope in two years time.

I'd be a little sceptical of the claim that "[c]ustomers opting for solar power can expect to reduce their energy bill by up to 50%", given that space heating is the single largest use of domestic energy. I guess it's all down to how you read that "up to" qualifier...
I think they meant that it was practical to replace half the electricity usage in the average house. Their web page quotes the average electricity usage of 3300kWhr/year and says that a 2kW rated array of panels will give about 1600kWhr/year.

This is reasonable but 3300kWhr/year is nowhere near the average total energy usage per house. It is nearer 8200kWhr/year the extra being mainly gas. It would take a 5 kW system to give 50% of that even on an ideally orientated site. I am not sure what Sharp panels they are using but Sharp's best gives 127W/m² To get 5kW output would need over 39m² of roof area. I doubt the percentage of UK homes with that area facing close to south is very high.

To get the area available on most UK house roofs to supply 50% of the total household energy would require extensive insulation and a ground sourced heat pump to amplify the electrical energy up to 3 or more times that in thermal energy.

Well, if you need heating, why would you try to address that with solar electric panels?  That's just silly, as there are much more efficient methods of using solar energy for heat.  Solar air or water heating can be something like 60% effective, compared to only about 15% effectiveness for electrical panels, and then the gross efficiency loss of converting that back to heat.  

Their site is focusing on electricity which is what the PV panels supply.  I don't understand the logical jump from electricity to energy here, given the acknowledged efficiency limitations of using PV for heating.  

The differences in efficiencies are not quite that big.

Solar water heating is something like 45% efficient despite what some vendors of solar thermal equipment claim. Have a look at the data on the CPC OEM on the Ritter Solar site. These are some of the best vacuum collectors going. Although the top line gives a eta zero value of 66%, that is the efficiency at zero temperature difference and 800W/m² insolation. The coefficients C1 & C2 show how much that degrades with temperature difference and lower insolation. Plug in ambient 15°C  and water 55°C and  700W/m²  and this drops to 60%. In addition the efficiency is quoted relative to the aperture area which is just the blackened area of the tubes despite mirrors that collect sunlight over the gross area. Quote the result relative to the gross area and it drops 48%  Furthermore the heat output is measured at the panel outlet and ignores losses in the pipework, heat exchanger and the  pump and controller energy.  90% efficient heat transfer from the output of the solar panel to the tank would be very good and would drop the overall efficiency of transfer of solar energy hitting the solar panel to the hot water tank to 43%

Solar panels  suitable for domestic use can achieve 18% efficiency at DC panel level (see Sunpower's SPR220 which will still give 17% efficiency at mains AC level with the best of inverters

However the real reason solar thermal cannot be used for heating in the UK for existing buildings is that most of the solar energy falls in the summer while heating is needed in the winter and there is no easy way of storing heat from season to season. This table shows that only 23% of London's solar energy falls in the six months Oct-Mar and 77% in the other six months. There have been schemes using very large underground heat stores and carefully designed passive solar heating buildings have been built but these need to be built from scratch and there is a very slow turnover of the UK housing stock so that such housing will not spread very fast if it is built at all.

However with a grid connected photovoltaic system you can sell excess energy to the power company in summer and buy it back in the winter when you need it. In effect the grid becomes like a vast battery.

If you use a ground sourced heat pump you can multiply up the electrical energy. Gains of three are reasonably obtainable and with a well insulated house and underfloor heating it is possible to heat the house with 35°C water and get an energy gain of 3.5  If the house has a large thermal mass then at the start and end of the heating season it is possible to use mainly off-peak electricity at night and buy it back  cheaper that you sold it for.

Thus 1kWhr of summer sun gives 0.17kWhr of summer electricity the sale of which will pay for 0.15kWhr of winter electricity which will give you 0.45kWhr of winter heat. This is 45% overall efficiency with season to season storage thrown in. It is however not a cheap solution as I know personally.


If I would like to heat my house in the winter with solar thermal power, there is a problem like you said. Little sunlight in the winter.

However, most solar thermal installations are rather small. 1-2 m^2.

What about just installing a thermal unit twice its size? The cost of the unit itself (that part at least) would be about 35% of the total, so I could double the capacity for little money.

Hello Richard
The amount of solar energy falling on 1m² of optimally inclined surface in the UK is from 1200 to 900 kWhr/year depending where you are. There is a useful map here. A solar thermal system will convert 40% to 50% of that to useful heat in your system. Say 45% of 1100kWhr equals about 500kWhr/m².year

However only 23% of that solar energy will fall in the winter six months. That is 115kWhr/m² of output spread over 6 months or 0.6kWhr/m² per day on average. This ignores the fact that vacuum tube systems are somewhat less efficient in cold weather and flat plate systems very much less efficient. That is bad enough but averaged over a shorter period it is much worse. I have both a solar thermal system (2.7m² aperture area) and a 17m² photovoltaic array (and a 10.8kW heat pump) Although I  have fitted flow gauges and thermocouples to the solar thermal system I have not yet connected them up. However the relative response of the two systems over time will fairly similar and the photovoltaic system is instrumented. I average about 46kWhr /week of electrical generation but in the first of June this year I generated 100kWhr while in the first week of January this year I generated 4kWhr all week. A solar thermal system would be expected to have the same sort of ratios.

Thus the 500kWhr/m² per year may be an average of  9.6kWhr/m² per week but you must expect 21kWhr/m² in the best week of summer and only 0.83kWhr/m² to last the whole  of the worst week of the winter. It depends on your house but you would be lucky to get through the worst week of winter with less than 200kWhr of heating (1.2kW continuously to heat the whole house and 500kWhr would not keep many less well insulated houses warm for a week in the depths of winter.

You would thus require 12m² of aperture area solar thermal system to make a 5% contribution to your 200kWhr week's heating. (or a 2% contribution to a 500kWhr heating requirement).

Even if you did invest in such a system and you had enough room for it (with a vacuum system this about 24m² gross area) you would find that in summer you would have weeks that gave you 250kWhr and that is more than you are likely to need for domestic hot water. You would have to spill some of that heat in a radiator or some such, wasting the output of your fairly expensive system.

Solar thermal systems in this country are a good way of providing almost all of your domestic hot water in the summer with useful contributions to some other form of heating in spring and autumn and a token contribution in winter. My 2.7m² system does just that and I installed myself for about £1900. Those that sell solar thermal system  for central heating in this country (and I have come across those that do) are plain dishonest.

Yes- I think that they really mean that the average home could cut their electricity bill by 50%.  A simply, 'accidental oversight' I'm sure :)

Seems like a good idea if it helps bring solar PV more into the public eye and helps it gain acceptance.  It would be great to move to where people are willing to pay for PV as a fashion accessory, like a wide-screen TV or expensive car, perhaps.

If you are interested in one person's experience of real-life solar in Holland, this is a great site...

Oily Bill

I have an 80 yard bank facing due south adjacent to my house (10 miles NBO of M/cr) on which I can erect an almost limitless array, (without the costs of roofing work etc.,) and have access to wholesale supplies.Doing most of the work myself I have examined the costs on a regular basis.

Even with grants - which are not as available as you might imagine the return, even factoring in 10% per annum electricity price rises, is well over 20 years - in which time you would be into complete replacement.

One factor that must be taken into account in any installation, is insurance for accidental damage (or high replacement / maintenance cost) both the Dutch and German experience is of high damage by kids - a company exists in Germany to repair panels.

As my array would overlook a school my insurers will not even consider it.

The CIS building in Manchester project the biggest use of Sharp panels in the UK uses 7,000 photovoltaic panels which they claim to produce "181,000 units of renewable electricity each year" - equivalent to the energy needed to power 55 homes for a year" (CIS press release)  = 127 panels per house.

The project started in 2004 at a total of £5.5m project which included a £885,000 grant from the Northwest Regional Development Agency (NWDA) and a £175,000 grant from the Department of Trade & Industry.It would not be unreasonable to assume that Sharp offered a very favourable panel price for this landmark project.Even so at 55 houses that = £100,000 per house give or take the odd penny.

One factor of course was that the 40 year old building required it's mosaic facing replacing anyway.

Read the full story here age

Oops missed out ...

Each megawatt hour (MWh) of electricity generated is eligible for benefits under the governments Renewable Energy Obligation Certification Scheme. The value of the certificates earned by the Tower is estimated to be approximately £9,271 per year.

Whoop di do.

As the building is listed, the blue panels (the only colour manufactured) have raised a lot of hackles amongst conservationists locally.

In the long run, why would damage from kids be that large a concern?  Do kids regularly go around breaking windows and/or burning houses down?  As solar panels become more accepted the unusualness that might attract attention for vandalism will disappear.  I'm not saying that changes the situation now, but in the long run I think such concerns will turn out to be meritless.  
Instead of pv on your 80 yard bank you could grow your own solar array from willow. With a three year coppice rotation you could provide your home with a sustainable and carbon neutral supply of useful energy to heat your house.
I don't have an 80 yard bank - but there is an area that willow could be relevant.
There are many types of willow available - assuming I want to run a log burner, rather than make cricket bats...

 - which is the type that has the growth factor for a 3 year rotation ?

Is there a good website reference?