Americans claimed more than $8 billion in climate-friendly tax credits under the Inflation Reduction Act last year, according to new data from the U.S. Treasury Department. That number is “significant” and higher than originally expected, officials said.

The majority of the money, more than $6 billion, went to households installing Solar panels on rooftops, small wind turbines and other renewable energy systemsAs the data shows, these loans were most popular in the sunny states, including much of the Southwest and Florida.

Loans that helped Americans to Energy efficiency of their homes By installing an electric heat pump or boiler, additional insulation, window replacement and other upgrades, these were most popular in the Northeast and Midwest.

A version of both tax breaks has existed for years, but they were expanded and extended as part of the Inflation Reduction Act of 2022, which invested at least $370 billion in clean energy programs across the U.S. economy. The tax incentives have proven so popular that the final cost of the law will likely be higher.

The new data from the Treasury Department provide a first detailed snapshot of how, by whom and where these more generous benefits were used in the first full year.

Wally Adeyemo, deputy finance minister, told reporters on Tuesday that the tax credits were “more popular than initially expected.”

More than 3.4 million households took advantage of at least one of these subsidies last year, resulting in total savings of more than $8 billion, according to the Treasury Department’s analysis. The bipartisan Joint Committee on Taxation had originally estimated the loans would cost $2.4 billion in the first year and about $4 billion in subsequent years.

The tax credit for solar panels was particularly popular, Treasury Department data shows. More than 750,000 American households claimed it last year. A tax credit for heat pumps was claimed on more than 260,000 tax returns. Some households may even have claimed both tax credits.

(Because the IRA expanded a previously expired tax credit for energy-efficient home improvements, some more efficient natural gas-powered appliances also became eligible for the subsidy.)

Former President Donald J. Trump has said that if elected in November and Republicans gain control of Congress, he will push for repeal of the Inflation Control Act, particularly the tax breaks for electric vehicle purchases that were not included in the Treasury Department’s new analysis. But in a letter to House Speaker Mike Johnson this week, 18 House Republicans opposed repeal, saying it would harm investment in the economy.

Mr Adeyemo stressed that the initial savings from the tax credits only told part of the story, pointing out that households that install solar panels and upgrade to more efficient appliances can expect lower electricity bills in the years to come.

The transition to clean energy will also help “prevent spikes in fossil fuel energy prices while improving the quality of the air we breathe and reducing carbon dioxide emissions,” Adeyemo said.

Treasury officials also stressed that nearly half of households claiming at least one of the tax credits had incomes of less than $100,000. But about 75 percent of all taxpayers had incomes of less than $100,000 in 2023, meaning the credits still disproportionately benefited wealthier taxpayers.

James M. Sallee, an energy economist at the University of California, Berkeley, said this distribution appears to be “significantly less regressive” than in previous years.

But he noted that tax credits tend to benefit wealthier people for a number of reasons: They require consumers to pay up front and wait until tax season to recoup the cost, and sometimes require itemized tax filings, which is more common among wealthier households. The IRA’s clean energy and energy efficiency tax credits also mostly apply to homeowners, who tend to be wealthier than renters.

“The IRA has tried to break that trend by limiting income from a number of benefits,” Dr. Sallee said. But, he added, “it’s hard to turn away from that when you’re operating through a tax code that favors the wealthy.”

The Inflation Reduction Act has funded some point-of-sale rebates that could help reduce upfront costs for more low- and moderate-income homeowners who want to purchase efficient appliances and make other improvements.

However, these refunds have been slower to roll out than the federal tax credits because state and tribal governments must set up programs to administer them. So far, only New York and Wisconsin have started their refund programs, but another 19 states and the District of Columbia have applied for funds and expect to be able to offer refunds by the end of the year.