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February 26, 2007



I wonder why the single unit is cheaper ($2.86 than $3.00 for the lot of 32?). Still, considering a european home that uses 3000kWh/year, you could install 80-90 of those panels (65m2 or 8x8m does that fit on my roof?!?) for about $12.000, which is not a very large investment!

I still think the surface area could a huge problem though!

Ronald Brak

I thought I'd work out how cheap a home solar electric system would have to be reach a break-even point where the money it saves would equal the payments on a 20 year loan.

So currently solar panels can be purchased for $3 a watt. This means a system that produces an average of 40 kilowatt-hours a day in a sunny area would cost around $30,000 and would save the owner about $1,500 a year (depending on local electricity costs). But even if your credit is good and you can borrow money at 7.5% the yearly payments on the loan would be about $2,900. The price would have to drop by almost half to $1.55 a watt or $15,500 for the whole system before the money you saved would pay for the entire cost of the loan.

If you have to borrow at 9% rather than 7.5% then your yearly payments would come to $3,240 and your savings wouldn't pay for the loan unless the price was about $1.38 a watt or under $14,000 for the whole system.

I believe solar electricity averages around a 4-5% decrease in price each year. If we assume a 4.5% yearly decrease in price then it will take about 16 years for it to come down to about $1.50 a watt. There fore I would not be surprised if point of use solar electricity becomes popular in 10 to 20 years time.

(I have not included installation and inverter costs. As I’m not sure how much they would cost.)

Eric T.

I live in a 14 year old home with a 8" thick concrete Trombe Wall. The area below the 180 sq. ft. of exterior glazing for the Trombe Wall is insulated over the concrete and sheathed with treated plywood stained the same color as the house. That 20 long south facing area of the wall is going to waste.
While reading the above blog I realized the best thing to do with the lower portion of the wall is install a row of sloar modules. I could fit 9 of the units featured above along the wall!
But they sell them in lots of 32.


Ronald Brak, I don't know where you get that number of 40kWh/day, but that's an insanely high number! I'm from the Netherlands where the average household uses 2908kWh/year, which is about 8kWh/day. Even though the average american household uses A LOT more, still that's only 10654kWh/year, which is 30kWh/day (http://www.eia.doe.gov/emeu/reps/enduse/er01_us.html). Personally I was quite shocked by this number. I knew that it was more, but I thought it was more like twice as much...
Anyway, 25% away from you 40 :o)

There is another mistake in your calculation though, because you cannot directly convert the numbers from Wp (the 42W given) to KWh.
This conversion (as you already noted) is very dependent on the location. I can only say that for systems in Europe, the conversion rate is about 0.6-1.5 kWh/Wp per year. This is based on data for crystalline panels though and I expect it to be higher for thin film (also because it works better under diffuse lighting conditions).
My guesstimate for numbers for thin film would be 0.8-2kWh/Wp

So, if we take these numbers into account and redo your calculations:

10654kWh/year would need 5327Wp installed (talking about your sunny area) which costs $15.981 at 3$/Wp. Indeed this doesn't take into account the inverters or the installation indeed, so it would be fair to say that the total cost could come to about 20k.

You are right if we are talking about less sunny locations, but I think the differences between electricity use in the households of Europe and the US indicate that there's a lot to gain in conservation, which could effectively half the electricity use & the investment costs...

Ronald Brak

I guess 40 kilowatt-hours a day for a household would be pretty high in most countries, but in Australia our houses are often all electric with electric stoves, water heaters, winter heating, air conditioning and so on. A consumption of 40 kilowatt-hours or more a day isn't unusual for a family of four here. (But the average Australian household only has about 2.5 people and the figure is probably similar in the United States.)

Now I will check my figures. A thousand watt solar panel will produce a kilowatt-hour of electricity after one hour in direct sunlight. But since the sun won't be shining directly on it all the time and sometimes there are clouds it would only generate an average of about 4 kilowatt-hours a day (This figure is slightly conservative for most of Australia.) This means a 10,000 watt system could average 40 kilowatt-hours a day. At $3 a watt that would be a $30,000 system.

If the panels are 10% efficient then the house will need 100 square meters of solar panel which is substanial, but the average house in Australia is 212 square meters.

Sky King

These panels are only about 5% efficient and have non conventional mounting - no aluminum frame, just four aluminum tabs on the back side. By the time you add mounting options and MC connectors, these panels are now $4.50/watt and they are only 42 watts each so I would need 60 instead of 15 190 watt panels and they are almost the same size as the traditional panels, so there is no way I would ever have room for 60 of these. They sound good at first blush, but once you look into it, they are a non starter.

Ronald Brak

I admit they don't pay for themselves at the moment. I could invest the money a home solar electric system would cost in a term deposit and the interest would be more than the money I'd save in electricity, even before installation costs. But if I was in a remote rural area useing a diesel generator, then they'd look pretty attractive. Once the price of solar power drops to about half or less of what it is now, then solar electricity will really take off as people could borrow to pay for a system and the money they would save on electricity would be enough to meet their loan payments.


Your analysis should consider Nanosolar, Heliovolt, and other CIGS producers that are starting to come on line with factory production. Some of these claim they will be profitable when selling for less than $1W. Combine this with BIPV for reduced mounting costs and you will have cost effective solar before 10 years. Welcome to the very beginnings of the "solar revolution".

Ronald Brak

I tend to be cynical about claims by any companies about rosy prospects for the future, however there does seem to be considerable evidence that significant price drops will occur in solar electric systems over the next few years. I certainly hope that we'll have $1 a watt solar electricity soon. I'm crossing my fingers and waiting to see.


These past few months I have done some research and see there is much more to learn about solar energy.

One thing I am thinking though, particularly in the context of the United States is the overall value when investing in Solar. In many States, once a person invests in a system, the government provides some rebate or tax credit. In addition when someone purchases a solar system, it appears the system itself retains much of its value. For example if I have a $150,000 house and invest in a $15,000 system, this adds value to the house. By what percentage, I do not know. Feedback would be appreciated on this. How much does a solar system depreciate per year?

The other point to consider is, in the event the government provides a low interest loan for a solar system, let's say 3%, how would this effect the overall picture.


Dong Wang

At present the general quote for poly or mono-crystalline solar panel is USD 3.70-3.80 per watt in China, and for the long term contracts the best quote is about USD 3.50 or EURO 2.65 per watt.

Though the thin film solar panel has cost advantage over poly or mono-crystalline solar panel, but its performance is not as good as poly or mono-crystalline solar panel. And many solar companies are developing new thin film solar panel technologies, and building new plants to produce thin film solar panels.

We are sure that the solar panel cost will be largely reduced soon. And the solar power will become our dominant power source.

To see more China solar energy industry information on http://solar-in-china.blogspot.com

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