Many climate experts say the long-term solution is to replace most of these fossil fuel-powered devices with electrical versions powered by a greener grid. But in practice it is difficult. While cities like Berkeley have rewritten building codes to ban new buildings from using gas, more than a dozen mostly red states have passed laws specifically banning cities from doing so. The question still remains, what to do with millions of existing homes.

Stephen Pantano, chief research officer at the Center for Law and Social Policy, said electrifying the heating could be a less intrusive way if they install a heat pump anyway if they buy central air conditioning. “We found that a relatively small investment of around $ 3 billion to $ 12 billion nationwide could have a big impact on energy use,” he said of the group’s new proposal. “It’s hard to come up with lots of ideas for so much money.”

An even more drastic strategy would be to replace more gas stoves with heat pumps so that the heat pump does practically all of the heating and cooling. But that could require larger heat pumps or additional electrical upgrades and other retrofits for many homes. His group’s proposal to simply replace the air conditioning systems is a more humble first step.

Berkeley, who pioneered the idea of ​​banning gas in new buildings, is now considering this approach. Only 10 percent of the city’s homes currently have air conditioning, but officials estimate that that percentage could triple in the hotter decades ahead. “Berkeley should work with air conditioning installers and heat pump manufacturers to ensure these homes install heat pump systems instead,” officials wrote in a recently released draft strategy for electrifying existing homes.

“This is a great idea,” said Jigar Shah, who heads the Department of Energy’s loan programs bureau. His office is looking for ways to help low-income Americans adopt technologies like heat pumps. “Heat pumps are not an untested technology,” he said. “We are really in a place where the time has come to make this bigger.”

Others were more careful. “There are places where electrification can be beneficial and places where it might not, and there are many details that have yet to be worked out,” said Francis Dietz, spokesman for the Air-Conditioning, Heating & Refrigeration Institute. and industrial trade group. For example, if more households turned to heat pumps instead of gas stoves, it could put a strain on electricity grids in winter, especially in colder parts of the country, he said.

There are other obstacles, too: many Americans are new to heat pumps, and some have had bad experiences with older models that didn’t work as well in cold weather. Although heat pump technology has improved significantly over the past decade, many building contractors remain suspicious. And of course the name “heat pump” doesn’t sound like a device that you want to install in the heat.