PG&E, a California power company, has placed an order for what are believed to be the world's two biggest photovoltaic solar farms, giving a strong endorsement to a technology that few power generators have yet considered to be ready for utility-scale use.

Between them the two farms, due to come on-stream in 2010 and 2011, are planned to generate 800 megawatts at peak capacity, or more than the 750 MW of the entire photovoltaic grid capacity in the US at the end of last year.