SunPower said Thursday it would build what could be the largest solar photovoltaic power plant in the United States to serve Florida Power & Light’s customers.

SunPower (NSDQ: SPWR) plans to construct a 25-megawatt plant in DeSoto County, Florida. The company, based in San Jose, Calif., also will build a second, 10-megawatt plant at NASA’s Kennedy Space Center for the Florida utility. 

Faced with growing political pressure to build cleaner power plants and reduce greenhouse gas emissions blamed for contributing to global warming, Florida Power & Light, like other utilities in Florida, is putting more money into renewable energy projects.

An energy bill recently signed by Florida Gov. Charlie Crist doesn’t contain specific requirements for utilities to buy a certain amount of renewable energy. But the law does direct the state Public Service Commission to draft renewable energy requirements, which would have to be approved by the state Legislature.

The law is partly in response to several executive orders signed by Crist in 2007, including one that asked the state’s Public Service Commission to require utilities to buy 20 percent of their power from renewable sources by 2020, especially solar and wind.

In addition to the two projects announced with SunPower Thursday, Florida Power & Light also plans to build a 75-megawatt solar thermal plant at an existing power station in Indiantown, Fla., starting in 2009. Solar thermal technology uses the sun’s heat to generate electricity. SunPower’s panels turn sunlight into electricity instead. The three projects will cost a total of $688 million. The company declined to break down the cost for each project. 

As more utilities invest in solar power, they also are outdoing each other in building larger and larger power plants. It was only back in May when Duke Energy trumpeted its 16-megawatt solar power project as being the country’s largest (see SunEdison to Build Largest U.S. PV Farm).

Investors seemed pleased with the news of the two SunPower projects. SunPower shares jumped 13 percent to reach $69.19 per share in recent trading. Florida Power & Light is a subsidiary of FPL Group (NYSE: FPL), whose shares rose 1.1 percent to reach $67.80 per share.

SunPower, which makes cells, panels and arrays, expects to complete the 25-megawatt project in 2009, and the 10-megawatt project in 2010.

The 25-megawatt plant would include SunPower's tracker system that tilts the panels to follow the sun's movement throughout the day. Electricity from both the 25-megawatt and the 10-megawatt plants would power about 4,100 homes. 

Both projects still need approval from the Florida Public Services Commission.

Florida is one of a growing number of states that is setting goals for reducing greenhouse gas emissions and offering tax breaks plus other incentives for utilities to build renewable energy projects. Governors from Pennsylvania and Massachusetts just signed energy bills over the past week (see Pennsylvania Governor to Sign $650M Energy Bill and Massachusetts Passes Sweeping Energy Bill).

California passed a comprehensive energy bill two years ago and is now devising plans to carry out the provisions (see California Offers Plan to Clean the Air).