At noon on a typical workday, technicians in a two-story control room monitor a dozen screens showing the heat generated by each array of mirrors. As temperatures creep past 700 degrees, icons blink to red from green, indicating the center is ready to feed electricity to the California grid.

Solar power "fits with our peak demand very well, as long as the sun is cooperating," says Michael Yackira, chief executive of Sierra Pacific Resources, the company that owns utilities serving Las Vegas and other Nevada cities. "When it's cloudy, when it's raining, when it's dark, it doesn't produce power."

A solar thermal unit that begins operation in 2010 will produce power at 14.2 cents a kilowatt hour, almost triple the 4.8 cents for a plant using pulverized coal, the Energy Information Administration estimates.

But costs for solar thermal may fall as low as 3.5 cents a kilowatt hour by 2020, according to a report commissioned by the U.S. Energy Department. Meanwhile, coal expenses may rise. Congress is considering limits on carbon dioxide and other greenhouse-gas emissions. The purchase of pollution permits may be required under a measure the Senate will begin debating next month.

Ausra's plants will produce electricity at 10 cents a kilowatt-hour starting in 2010, and the price will fall to 8 cents a few years later, as it adopts systems with fewer parts that will be less costly when widely deployed, the company says.

"We are going to beat coal," says Bob Fishman, Ausra's chief executive officer. His company has a contract with PG&E Corp.'s Pacific Gas & Electric for a site in central California.

Chevron, Goldman Sachs, FPL, PG&E and other companies have filed more than 50 applications with the Bureau of Land Management to lease government-owned desert property for solar power systems. Chevron, which has invested in the solar thermal builder BrightSource Energy Inc. in Oakland, Calif., and Goldman, the biggest U.S. securities firm, declined to comment.

Google's philanthropic division put $10 million into eSolar, a start-up in Pasadena, Calif. Dan Reicher, a former Energy Department official who manages the unit's climate and energy initiatives, said there will be more such investments.