[maxerickson]

Power is quite a lot higher:

http://en.wikipedia.org/wiki/Insolation#Earth.27s_insolation

(the 250 W/m^2 there is the 24 hour average)

[breischl]

From the link

>> Ignoring clouds, the daily average irradiance for the Earth is approximately 250 W/m2

Emphasis added. Seems like clouds might be a non-trivial factor, yes?

[maxerickson]

Yeah, clouds matter (obviously, locations vary). GP used an extremely conservative value for the energy available, I was just pointing to a less conservative value.

(The difference between the values is ~8x, I doubt clouds have that big an impact in very many locations)