Electric heat pumps, the most affordable and energy efficient way to heat and cool homes, continue to outsell gas furnaces nationwide. They can also reduce outdoor pollution and, as a result, save lives, according to a report issued on Tuesday.

The study, by Rewiring America, a nonprofit group that promotes electrification, calculated that if every American household got rid of furnaces, hot water heaters and clothes dryers powered by oil or gas and replaced them with heat pumps and electric appliances, annual greenhouse gas emissions could drop by about 400 million metric tons. Fine airborne particulate matter and other air pollutants could decrease by 300,000 tons, the equivalent of taking 40 million cars off the road.

Roughly two-thirds of the country’s households burn fossil fuels such as natural gas, propane and fuel oil for heat, hot water and drying clothes, releasing nitrogen oxides and other pollutants into the air.

While a transition to electric appliances could shave $60 billion off people’s annual energy bills, it could also deliver important health rewards, researchers found. It could prevent 3,400 fewer premature deaths per year, 1,300 fewer hospital visits and 220,000 fewer asthma attacks, all of which amounted to about $40 billion in benefits, according to the study.

“Just swapping out appliances, it’s eye-opening in terms of the significant impacts,” said Wael Kanj, senior research associate with Rewiring America and the lead author on the report.

The amount of pollution reduction would depend on whether the electricity needed was generated by low-carbon sources like wind and solar power or came from gas or coal-fired power plants.

“The report rightly highlights the need to produce clean energy,” Rob Jackson, a climate scientist at Stanford University who has researched the health impacts of gas stoves, wrote in an email. “Electrifying our homes will have fewer benefits in West Virginia, where around 90 percent of electricity comes from dirty coal, than in other states with cleaner electricity.”

Mr. Kanj said if the grid decarbonized faster than forecast, the pollution reductions and health benefits would increase.

Yifang Zhu, a professor at the U.C.L.A. Fielding School of Public Health and an expert in air pollution, said the ways household appliances affected outdoor air pollution had largely gone understudied and that the new research helped fill in a gap. “Every sector needs to be looked at,” she said. “People can realize there are more benefits than just improved indoor air quality by electrifying households.”

The effect of gas stoves on indoor air came into sharp focus this past year after a study linked their use to up to 19,000 deaths in the United States and 50,000 cases of childhood asthma.

More American households are moving to heat pumps, which have outsold gas furnaces in recent years and are on pace to do so again in 2024.

The report from Rewiring America, titled “Breathe Easy,” drew from data, analyses and reports from a series of government agencies, including the National Renewable Energy Laboratory, the Environmental Protection Agency, the U.S. Census Bureau and the Energy Information Administration.

The American Gas Association, an industry group, contested the findings. A spokeswoman, Emily Carlin, pointed to the association’s own research, which found that it cost less to use natural gas in a new home compared to going all-electric. The group’s research found that high-efficiency natural gas appliances could yield fewer greenhouse gas emissions compared to an all-electric household and said that reductions in greenhouse gas emissions were similar to that of a heat pump in a colder climate.

The association also highlighted a study funded by the World Health Organization that found no significant increased asthma risk from home gas use compared with electricity, and a lower risk of bronchitis, though that study did find a possible increased risk of pneumonia and obstructive pulmonary disease.

Amy Andryszak, president and chief executive of the Interstate Natural Gas Association of America, called the study “inherently flawed” and said its calculations did not include increased costs on an electric grid that would come with getting rid of natural gas. “This not a serious study, but rather an attempt to secure headlines with the same false and misleading talking points that activists have been using for years,” she said.

Under the Inflation Reduction Act, the federal government allocated nearly $9 billion in home energy rebates for eclectic appliances and energy efficient home retrofits. In 2023, more than 250,000 families claimed federal tax credits for heat pumps and more than 100,000 families claimed credits for heat pump water heaters. President-elect Donald J. Trump has said he wants to repeal the law. It’s unclear what that could mean for heat pump adoption, as many of the rebate funds have already been allocated to states.