California is studying power plant emissions in a move towards what would be one of the first US state restrictions on heat-trapping gases such as carbon dioxide.

The move is part of California's growing effort to try to control climate change and reduce the risks of environmental damage to the state's economy and resources.

If adopted by the state, the regulations would affect some of California's biggest energy companies.

The state will hold a conference this month to begin identifying "best practices" for companies to lead to energy savings and reduced emissions. These practices could eventually lead to actual regulations.

The measures may include more fuel-efficient fleet vehicles, new efficiency standards for buildings and appliances and improved power plant operations, a representative told Reuters.

In December, long-term power procurement plans for utilities to ensure California has enough electricity to serve growing demand were put in place, with the proviso that energy efficiency and conservation should come first.

The regulators also directed the utilities to factor in a "carbon adder" when they purchase electricity supplies, a financial tool to measure the cost of generating electricity by coal and gas versus the cost of renewable resources and energy savings.

It is hoped that when utilities look at their costs, they will have an incentive to turn toward more energy efficient and renewable resources.