Two years after President Joe Biden’s landmark climate law was signed, millions of Americans have used it to save millions of dollars on solar panels, appliances and home insulation.

Inflation Reduction Act tax credits for residential energy upgrades are going gangbusters, recent Treasury Department data shows, with more than 3.4 million households claiming $8.4 billion to help offset the cost of rooftop solar panels, solar water heaters, home batteries and heat pumps.

Americans are also using the tax credits to update their homes with new insulation that’s better at maintaining indoor temperatures and sealing their windows and doors so the cool air doesn’t pour out of the house into the summer heat.

White House national climate adviser Ali Zaidi told CNN the data shows the Inflation Reduction Act has “overachieved” in its first year – a remarkable success since polling has shown few Americans know anything about it.

“Across the board, when it comes to opening up choice to more affordable energy technologies, people are very much responding to that,” Zaidi said.

Rooftop solar and home insulation are the most popular home upgrades among Americans taking advantage of the cash; 752,000 households claimed credits for rooftop solar in the United States, while nearly 700,000 households claimed credits to insulate their homes and another 649,000 claimed credits to help seal their windows.

Tax credits for heat pumps – energy-efficient appliances that can both heat and cool homes – are being claimed at lower numbers, with around 268,000 households claiming credits for them and another 100,000 households claiming credits for heat pump water heaters.

Ari Matusiak, CEO of electrification nonprofit Rewiring America, told CNN more people may be jumping at the chance to buy solar panels than heat pumps because they are new features to add to a home. Most consumers aren’t going to run out and buy an electric heat pump until their current HVAC breaks.

Still, Matusiak pointed to signs of growth for these hyper-efficient heating and cooling systems.

“When you look at industry data overall, you can see that heat pumps are outpacing fossil fuel alternatives for the last two years, and that the gap is widening,” Matusiak told CNN. “Households are moving toward an electric future.”

The Treasury Department puts EV tax credits in a different bucket from residential ones, because Americans claim their vehicle tax credits directly at the dealership. Still, Americans have claimed over $1.5 billion worth of tax credits off 216,000 clean vehicles since January of this year.

And looking around the country, three states – California, Texas and Florida – make up more than 40% of the total credits claimed.

Speaking to reporters on Tuesday, White House senior adviser for international climate policy John Podesta said he believed many IRA tax credits had sticking power and would be difficult to repeal even if former President Donald Trump and Republicans are elected in November.

“I think particularly the Inflation Reduction Act tax credits are very solid,” Podesta said.