Well... let's do the math! Incident solar radiation is about 1 kW per meter squared. Assume 10% end to end efficiency (including solar -> electric, storage, an

Well... let's do the math! Incident solar radiation is about 1 kW per meter squared. Assume 10% end to end efficiency (including solar -> electric, storage, and actual charging efficiency... this is optimistic, but doable... certainly not the cheapest though). You now need 10 square meters of panel to supply 1 kW. Assume sun is out for 12 hours a day, and for the full 12 hours you get all 1 kW/m^2 incident radiation (this is very very generous). The car has a 60kWh battery. So if we want to find out how much panel it takes for one station to charge one car a day... 60kWh to charge, but 12 hours to charge it up, so you basically need 5kW, which is 50 m^2 of panel. Which honestly isn't -THAT- big. Its a 7 meter square. Now... from my random snooping around, and my own impressions, I would say that a 'large' gas station typically covers something like... 500-600 meters squares (thats 5300 to 6500 square feet). That would be enough to super optimistically charge 10-12 cars a day. I saw optimistic, because incident solar radiation is not that kind. Can take a looksey here: http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/ http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook... If you pick average, annual, and single axis east-west tracking (which I believe is the best bang for the buck), you see on the solar map, the BEST places in the US gets 5-6 kWh/m^2/day, compared to our assumption of 12 kWh/m^2/day. The feasibility of superchargers being even 90% off the grid is of course completely dependent on the ratio of size of supercharger panel array and rate of cars charging. But given the above, I'm inclined to believe that it is highly impractical for the majority of super charger stations to become actually self reliant, especially in high traffic areas.