A proposal by Sen. Joe Simitian, D-Palo Alto, to require California utilities to obtain a greater share of their electricity from renewable sources is now one signature away from becoming the law of the land.

Simitian's proposal, known as Senate Bill 2X, passed the Assembly today 55-19 and is now heading to Gov. Jerry Brown for final approval. The bill cleared the state Senate in February.

Simitian's bill would require utilities to obtain 33 percent of their electricity from renewable energy sources such as solar, wind or geothermal technology by 2020. Currently, the utilities are required to meet a 20 percent target for renewable energy by 2020.

"This bill establishes California as the national leader in clean energy, improving the environment and stimulating the economy, while protecting ratepayers from excessive costs," Simitian said in a prepared statement after the Assembly vote.

Simitian has tried to raise the renewable-energy standards in the past only to see his bill vetoed by former Gov. Arnold Schwarzenegger. The new bill would also allow utilities to get exemptions from the California Public Utility Commission if the costs of acquiring renewable energy or plugging into the state's power grid prove too steep.

The new law would apply to both investor-owned utilities such as PG&E and to municipal utilities. The city already has a goal of getting 33 percent of its electric load from renewable sources by 2015.

In his statement, Simitian expressed optimism that the rising costs of fossil fuels and the growing demand for energy would continue to make renewable sources more viable. He also said the new mandate will encourage green energy providers to come to California.

"Senate Bill 2X sends a signal to renewable energy providers that California wants them here," Simitian said. "They will respond, as they have in the past, with billions of dollars in investments that will provide jobs and tax revenues."