If your April PG&E bill seems lower than usual, it's not a mistake.

Millions of California households will see a credit averaging $35 on their April electricity bill thanks to the state's groundbreaking efforts to address climate change through several efforts, including the landmark cap-and-trade program.

Residential customers of the state's three investor-owned utilities -- PG&E, Southern California Edison and San Diego Gas & Electric -- will automatically receive the so-called "climate credit" this month. The credit, which is $29.82 for PG&E customers, is given to each household regardless of energy consumption or bill amount. A second credit will appear on October bills. The twice-a-year climate credits are expected to be paid through 2020.

The credit comes from payments by power plants and industries that are required to reduce their emissions of greenhouse gases.

California launched its first auction of greenhouse gas emission permits in November 2012, marking the first effort in the nation to put a price on carbon pollution. Utilities including PG&E were given free carbon permits for the first year but had to agree to sell those permits in the auction. State legislators fought to ensure that some of the auction proceeds flowed back to ratepayers.

Small businesses will receive the climate credit every month, as a credit related to the amount of electricity used.

State regulators hope that households will use the savings to invest in energy efficiency, such as LED lighting or smart thermostats.

"The climate credit is part of an array of programs developed by California to fight climate change and improve air quality," Mary Nichols, chairwoman of the California Air Resources Board said in a prepared statement. "If homeowners and businesses use the credit to purchase some of the newest energy-efficient light bulbs or other energy-saving equipment, they will save even more."

The total amount of money to be returned to ratepayers between 2013 and 2020 is expected to range from $5.7 billion to $22.6 billion.

Contact Dana Hull at 408-920-2706. Follow her at Twitter.com/danahull.