Governor Jerry Brown has outlined a multi-billion dollar plan to help Californians buy electric vehicles and vastly expand the network of charging stations.

Brown says he wants to see five million zero-emission cars on the state’s roads by 2030.

The ambitious proposal to transform California’s car culture comes as he begins his final year in office and works to set the stage for his environmental legacy to continue under his successor.

The Democratic governor has positioned California as a global leader in fighting climate change, placing him in direct opposition to President Donald Trump, a climate-change denier who has pulled the US out of the Paris climate accord.

The number of zero-emission cars is a significant expansion of Brown’s former goal of seeing 1.5 million such vehicles by 2025. Some 350,000 carbon-free vehicles are already on California’s roads.

Reaching the goal will require 40 per cent of vehicles sold in 2030 to be clean, said Mary Nichols, chairwoman of the California Air Resources Board, up from about 5 per cent now.

“We think that’s a very reasonable proposal,” Nichols said. “It’s not a stretch.”

Brown’s $2.5 billion ($A3.5 billion) plan, which still needs legislative approval, .would extend subsidies to help people buy emission-free vehicles while also building the infrastructure needed to support them.

If approved there will be 250,000 electric-vehicle charging stations and 200 hydrogen fuelling stations, an increase from about 14,000 charging stations and 31 hydrogen stations.

California offers subsidies of up to $US7,000 for the purchase or lease of a new electric, fuel-cell or plug-in hybrid vehicle, though most subsidies are smaller.

-AAP