The California Public Utilities Commission estimates that reaching that goal could propel energy costs to nearly 11% above what they would be from gas-fired energy plants.
While 30 other states have also set requirements for power companies to utilize more renewable energy, their mandates are far more modest. Obama has been unsuccessful in his efforts to persuade Congress to pass a national mandate, and the prospects for Washington embracing more California-style energy policies is unclear.
In his State of the Union address last month, the president implored Congress to take action to cut the nation's pollution. Though he did not outline specific initiatives, he said he would take executive action to protect the environment if Congress declined to act.
"If Congress won't act soon to protect future generations, I will," Obama said.
Brown, meanwhile, is taking his green message overseas. In April, he is scheduled to visit China on a weeklong trade mission and will make climate change a centerpiece of his activities there, his aides say.