2000kCal = 2.3kWh Assuming 5% conversion efficiency (http://en.wikipedia.org/wiki/Photosynthetic_efficiency http://en.wikipedia.org/wiki/Photosynthetic_efficien

2000kCal = 2.3kWh Assuming 5% conversion efficiency (http://en.wikipedia.org/wiki/Photosynthetic_efficiency http://en.wikipedia.org/wiki/Photosynthetic_efficiency) Win = 46.5kWh. "standard" solar radiation equals approximately 1kW/m^2, so given 12 hours of solar exposure per day this works out to about 3.9 square meters. Whenever I do these kinds of calculations I'm always amazed at how much power the sun is able to provide on a square meter 93E6 miles away!