NRG Energy and SunPower announced the first 22 MW of its California Valley Solar Ranch entered the grid from its site in San Luis Obispo County. Electricity from the project is contracted by state utility Pacific Gas and Electric for 25 years.
PG&E Senior Vice President Fong Wan said the project helped balance the state's energy portfolio.
"This project will play an important role in our efforts to meet California's 33 percent renewable portfolio standard and make progress toward a clean energy future for all Californians," he said in a statement.
The entire project is expected to be online by the end of the year. Once fully operational, it would provide enough solar power to meet the annual energy demands of 100,000 homes.
Last week, U.S. Secretary of Interior Ken Salazar announced the government established a preliminary set of 17 solar energy zones in Arizona, California, Colorado, Nevada, New Mexico and Utah.
The program sets up a blueprint for utility-scale solar power projects in western United States. The Interior Department said as much as 23,700 MW of solar energy could be developed on the sites.