I did some calculations a while back. The problem isn't the cost of the panels, it's that the sun really doesn't put all that much energy onto the earth- we would have to pave an incredibly large number of square miles of earth to satisfy the energy needs of a major western nation.

FYI, it would literally take a solar panel larger than Wales to supply UK with your annual electrical consuption. And probably require most of Scotland to be turned into hydoelectric resevoirs to feed the grid at night and on rainy/cloudy days.


Assumptions/Constants:
* Average Solar Flux for North America: 150 W/m2 -This is representative of the US Northeast and Europe, and accounts for weather.
* Best Average Solar Flux in the US southwest is 240 W/m2
* Northern US December average 71 W/m2
* Winter levels will be appx 80% of this value
* US Annual Energy Consumption in 2003: 6.22 ExaWatt-hours (equivilent to 325 billion tons of oil)
* Typical electrically heated household energy use during coldest week of winter: 24,000W
* Typical instantaneous power requirement for a refrigerator: 1200W
* Combined contribution of solar, geothermal and wind in 2003: less than 2%
* Solar Panel Efficiency: 8.25% (commercially mass produced a-Si, the only feasible material at the scale we're talking! See Unisolar whitepaper #1 below.)
* Thermal de-rating of solar panels for US winter weather: 15% for a-Si, 35% for crystalline silicon.
* Typical loss due to dirt, dust, etc: 3%+
* Inverter efficiency: 94%
* Wiring efficiency: 97%
* Transformer efficiency: 95%
* Battery efficiency: 80%

* Energy required to manufacture a-Si panels:120 kWh/m2 (432 MJ/m2) as a generously conservative estimate. I don't know if this counts mining, refining, transportation, installation, cabling, power conversion, substations, transmission, etc, etc and I'm pretty sure it doesn't.
* Energy required to mount an a-Si panel: appx 120 kWh/m2 (432 MJ/m2)

* Solar energy absorbed annually per m2 in US Southwest desert:
365 days * 24 hours * 240W/m2 = 2,100 kWh

* Solar energy absorbed annually per m2 in US Northeast:
365 days * 24 hours * 150W/m2 = 1,314 kWh

* Losses in conversion, wiring, etc:
.97 * .94 * .97 * .95 * .80 = 32% loss, 67% efficiency

* Break-even point for energy for a-Si Solar Panels and installation in US Southwest desert:
240kWh/m2 / (240W/m2 * 8.25% * 67% * 24 * 365) = 2.1 years

* Break-even point for energy for a-Si Solar Panels and installation in US Northeast:
240kWh /m2 / (150W/m2 * 8.25% * 67% * 24 * 365) = 3.2 years

For this that missed the significance of this, it means spending 2-3x our entire annual energy consumption on solar panel production alone.

If the south-facing roof of a 200m2 (~2000ft2) typical house in the Arizona desert was covered in a-Si solar panels:
240W/m2 * 100 m2 * 8.25% * 67% = 1300W (about enough to run a refrigerator)

If the south-facing roof of a 200m2 (~2000ft2) typical house in the US was covered in a-Si solar panels:
150W/m2 * 100 m2 * 8.25% * 67% = 829W (about enough to run a typical PC desktop with 17" CRT monitor). It would take 42 houses like this to provide the energy one house requires for electric heating.

If the south-facing roof of a 200m2 (~2000ft2) typical house in the US Northeast in winter was covered in a-Si solar panels (assuming no snow):
71W/m2 * 100 m2 * 8.25% * 67% * .85 = 321W (4 houses combined could run a Mr. Coffee). It would take 75 houses like this to provide the energy one house requires for electric heating.

Cost of 8% efficient a-Si solar panel: appx $1000/m2
Cost of installation: appx $100/m2
Cost of 10kW inverter: $12000 (For surge. An electric range draws 10kW.)
Cost of storage batteries: $200/kWh
Cost of cabling: appx 1x material cost
Cost of electrical installation: appx 2x electrical material cost

100m2 of solar panels: $100,000
Cost of panel installion: $10,000
Batteries required to store 2 day’s worth of energy at 1300W average: $13,000
Cost of inverter: $12000
Cost of electrical installation: $50,000
Total cost of 1300W Arizona or 564W northeast partially-solar-powered house calculated for above: $185,000.

Area of solar panels in the southwest US desert required to supply US with total electricity demands:
6.22Ewh / (1300W * 24 * 365) = 54,000 km2

Number house-sized solar panels spread evenly throughout the US required to supply US with total electricity demands:
6.22Ewh / (829W * 24 * 365) = 856 million house-sized panels (compared to 120 million households in the US, which includes aparments and townhouses)- works out to about a quarter acre of solar panels per every family in the US. BUT, that's lopsided as most of that comes from the summer. If we go by straight winter values, it works out to closer to 17 acres of solar panels per family.

US GDP: $ 11.75 trillion
856 million house-sized panels: $158 trillion


Sources: http://www.eia.doe.gov/emeu/cabs/usa.html http://www.johnstonsarchive.net/environment/solartechnote.html http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_2.pdf http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_1.pdf http://www.nrel.gov/docs/fy04osti/35489.pdf http://en.wikipedia.org/wiki/Solar_power


Since we're using very large numbers here:
1,000 Thousand Kilo k
1,000,000 Million Mega M
1,000,000,000 Billion Giga G
1,000,000,000,000 Trillion Tera T
1,000,000,000,000,000 Quadrillion Peta P
1,000,000,000,000,000,000 Quinillion Exa E

[This message has been edited by SteveFehr (edited 08-12-2006).]