Californian Governor Arnold Schwarzenegger has set a goal of building a million solar roofs within 10 years, and solar energy is expected to play an important role in the PUC's investigations into achieving 33% of the state's power generation from renewable sources by 2020.

The additional $US300 million will be made available through the PUC's Self Generation Incentive Program for solar systems with a capacity of more than 30kW, typically installed by businesses.

Clean energy advocate Bernadette Del Chiaro, of Environment California, welcomed the increased funding for solar energy, saying the need for increased alternative energy infrastructure had never been greater.

"The PUC has essentially cocked the gun aimed at a robust solar program for all Californians to enjoy and we are anxious for them to pull the trigger, bringing 3000MW of much-needed clean energy capacity to the state," she said.

The Million Solar Roofs Bill is yet to become legislated policy in California, but Schwarzenegger has said he will make sufficient rebates available to residents and businesses through the PUC.