12.5 Square Miles of Solar Panels:

Two massive solar power plants are planned for central California.

The plants will cover 12.5 square miles of central California with solar panels, and in the middle of a sunny day will generate about 800 megawatts of power, roughly equal to the size of a large coal-burning power plant or a small nuclear plant.

The power will be sold to Pacific Gas & Electric, which is under a state mandate to get 20 percent of its electricity from renewable sources by 2010. The utility said that it expected the new plants, which will use photovoltaic technology to turn sunlight directly into electricity, to be competitive with other renewable energy sources, including wind turbines and solar thermal plants, which use the sun's heat to boil water. . . .

Though the California installations will generate 800 megawatts at times when the sun is shining brightly, they will operate for fewer hours of the year than a coal or nuclear plant would and so will produce a third or less as much total electricity.

the plants are a big step for solar power, but they also highlight solar power's limitations: the need for over 35 square miles of solar panels to generate the same amount of power as a single coal plant, but without the same level of reliability.