In another PF thread it was proposed to build a centralized PV farm of 1000 gigawatts , which is the order of magnitude of US installed generating capacity. It'd cover 1/10 the area of New Mexico, Arizona and Nevada. √ (10%of 896815 km^2) = 299.5 km per side, 186 miles per side, not far from the 150 stated earlier in the same thread. Close enough for thought experiments. You can't drive maintenance trucks over solar panels so the dimensions will expand to accommodate roadways. Unless they're elevated to serve as rooftops with access from below. Stormwater runoff from a 150 mile square rooftop will be a challenge, Phoenix area has been known to get 6 inches in a storm. http://www.fcd.maricopa.gov/Weather/Rainfall/raininfo.aspx [Broken] It'd be interesting that's for sure. Myself, i am far more afraid of huge storage batteries than of reactors. I wouldn't be go anywhere near them. Maybe @anorlunda will assess the practicality of moving so much power over so much distance.