California officials advanced a proposal to require zero-emission space and water heaters, a move that could lead to an effective ban of new natural gas in heaters for commercial and residential buildings in the state.

The California Air Resources Board voted on Sept. 22 to adopt the 2022 state implementation plan, which is aimed at cutting emissions to meet the U.S. Environmental Protection Agency National Ambient Air Quality Standards for ground-level ozone. Under one included provision, all new space and water heaters sold in California for new construction or building retrofits would need to meet a zero-emission standard beginning in 2030.

The plan does not call specifically for a natural gas ban in new heaters, but CARB officials say the regulation would likely rely heavily on electric heat pumps. 

Nine of California’s 35 local air districts already regulate nitrogen oxides emissions from heaters. But even with low limits in place, CARB projects that NOx emissions from natural gas combustion in residential and commercial buildings will total 37.7 tons per day in 2030 and 36.2 tpd in 2037. CARB estimates the proposed standards would reduce NOx emissions by 13.5 tons per day by 2037. 

Natural gas distribution utility SoCalGas supports state efforts to meet federal air quality standards, Christine Detz, a utility spokesperson, said in a statement. The utility’s infrastructure and operating experience will be critical in delivering clean energy in the long term, she added.

“A growing body of research shows that electrification combined with clean fuels and carbon management deliver the most affordable, resilient and technologically proven path to improved air quality and full carbon neutrality,” Detz said.

CARB staff will still need to hash out details of the standards. They will work with the U.S. Dept. of Energy, California Energy Commission and California Building Standards Commission, Housing and Community Development to develop them, according to a staff report.

CARB aims to hold a public hearing on the standards in 2025. 

Environmental advocates have increasingly called for natural gas bans. Buildings account for 14% of new greenhouse gas emissions in the U.S., according to Sierra Club. In August, it was one of 26 groups that petitioned the U.S. Environmental Protection Agency to add zero-emission standards for new water and space heaters.

Earlier this year, Washington became the first state to require electric heat pumps in all new commercial buildings over the objections of the gas sector and state contractor groups. Officials in dozens of cities, including Los Angeles this summer, have passed natural gas bans for new buildings. 

Natural Resources Defense Council representative Sylvie Ashford said during the CARB meeting that the “proposal will accelerate the electrification of residential and commercial buildings, which is critical for meeting California’s climate goals.” She also called on CARB to seek community engagement and collaboration to ensure that residents are able to switch from gas to electric for space and water heating.