Josh Karkos of Karkos Heating Services in Lewiston hooks up a heat pump at a Lewiston home in 2019. Daryn Slover/Sun Journal

Maine’s Janet Mills was among a group of governors and national climate leaders in New York Thursday to announce a goal of installing 20 million heat pumps in U.S. homes by 2030.

Mills is co-chair of the U.S. Climate Alliance, a coalition of almost exclusively Democrat-led states that formed in 2017 after then-President Donald Trump pulled the country out of the Paris Agreement, a global accord to combat climate change.

Over the last six years, the alliance has encouraged policies that reduce carbon emissions and reliance on fossil fuels, but Thursday’s announcement was the group’s most ambitious yet. The announcement of a national goal comes as Maine has aggressively ramped up conversions to heat pumps with tax credits and rebates, an effort that Mills said will continue.

White House climate adviser Ali Zaidi, who joined the governors for the announcement, said heat pumps are the closest thing to a moonshot that the U.S. has in beating back climate change, and he praised states like Maine for aggressively promoting their use.

“We’ve got governors on the stage and represented in this room that have produced the kind of inventive spirit that really matches the urgency of this moment,” he said.

Mills shared the stage with New York Gov. Kathy Hochul, Washington Gov. Jay Inslee, alliance Executive Director Casey Katims and Zaidi.


In her remarks, Mills recounted how her administration set a goal of installing 100,000 heat pumps in Maine homes by 2025, a goal that already has been surpassed.

“Now 100,000 may not sound like a lot to people in the Big Apple,” she said. “But (for Maine) that’s a pretty good number. We’re on our way and we’re not stopping there.”

This summer, Mills updated her goal to include an additional 175,000 heat pump installations by 2027. She also has set a goal of reducing greenhouse gas emissions in Maine by 45% by 2030 and 80% by 2050.

According to information provided by the U.S. Climate Alliance, 4.7 million heat pumps have been installed across the country. The goal is to increase that to 20 million by the end of the decade.

Heat pumps, which run on electricity, can both heat and cool buildings and often replace oil or gas furnaces, which are a major contributor to greenhouse gases. The pumps extract heat from outdoor air or underground and transfer it inside, instead of heating up a coil in a furnace, for instance. They also pull heat from indoors and dump it outside or underground, thereby cooling homes down.

Hochul said the U.S. is long past the point of inaction and cited the many climate-related natural disasters that have occurred just this year.


“We’re the first generation to really feel the effects of climate change … and indeed the last generation that can do anything meaningful about it,” she said. “This is not an impending threat but something that is in the here and now. Shame on all of us if we don’t act with urgency.”

Inslee, who was one of three governors to launch the alliance (along with California’s Jerry Brown and New York’s Andrew Cuomo), called heat pumps the “most beautiful technology since the wool sock.”

He also said they are unfortunately named because they cool just as much as they heat.

“We want to be warm in winter and cool in summer and prevent the climate from collapsing all year long,” he said. “Heat pumps are the only thing that can do all three.”


To help achieve the goal, the Biden administration included in the U.S. Inflation Reduction Act a 30% tax credit for heat pump installations. Other states and utilities offer additional tax credits on top of that, including Maine, which provides a rebate of up to $2,400 on two units.


Mills said Maine has long been reliant on oil for heat and said heat pumps address that while also reducing costs for consumers.

“I sound like a salesperson … and I guess I am,” she said, adding that there are 23 heat pumps installed at the Blaine House, the governor’s mansion.

Alexandra Rempel, associate professor of environmental studies at the University of Oregon, told The Associated Press that heat pumps are indeed more sustainable than traditional heating and cooling systems, but they are not highly efficient in extremely cold regions. Like other systems, they use refrigerants – chemical fluids that significantly warm the atmosphere when they leak. They also draw power from the same electrical grid as everything else, which is often powered by fossil fuels, so their sustainability depends in part on the amount of green energy generated in that region, she pointed out.

“Overall, the benefits do outweigh the limitations in most places, but there are some limitations,” she said.

Mills’ predecessor, Republican Paul LePage, was a big proponent of heat pumps, too, but the U.S. Climate Alliance is decidedly not bipartisan. Of the 25 member states, only Vermont has a Republican governor. Many Republican elected officials either deny that climate change is a problem or that fossil fuels are the major contributor, despite overwhelming scientific evidence to the contrary. The government support and increased demand for heat pumps have gotten some pushback from the oil and gas industry, as well. Some critics have pointed out that much of the electricity that’s consumed still comes from fossil fuels. In Maine, roughly half of electricity consumed comes from renewable sources.

Maine, which is among the coldest states, has not seen widespread problems with heat pumps. And roughly half of electricity consumed by Maine people comes from renewable sources, which means converting homes from oil heat to heat pumps can significantly reduce fossil fuel use.

Mills said that in addition to reducing costs to homeowners and slowing climate change, installing more heat pumps creates jobs. The state has worked closely with the community college system to train a generation of installers.

Zaidi, the White House climate adviser, said he’s been inspired to watch states like Maine become leaders on climate change.

“So often when we talk about climate change, we talk about it in the horror that it’s producing for our communities,” he said. “And it’s really easy to take all of that in and get resigned to that sense of doom and despair. But this coalition and the action you’re all taking tells a different story.”

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