Heat pumps cut home-based carbon emissions. But the market is a bit cold.

When it comes to the clean energy transition, electric vehicles and solar panels get a lot of the attention. But there are less sexy heavy hitters too.

Home heating and cooling account for one-fifth of the country’s carbon emissions. There’s a solution to that problem: heat pumps. They can warm your water, heat and cool your house, all while generating way less carbon than burning fossil fuels in a furnace or boiler.

Only, they’re not really catching on. In fact, heat pump investments in the U.S. have actually decreased slightly this year.

Heat pumps are most popular in the South, but they’ve also got fans in places that get Maine-in-February cold.

“When it gets down to, like, 10 degrees or whatever, the heat pumps are sufficient for heating,” said homeowner Nathan Wilcox. He didn’t let the winters in Portland, Maine, deter him from making the switch to heat pumps in 2022.

“So we’re outside … so that’s the outside unit,” Wilcox said while giving the grand tour of his century-old home, or rather its heating and air conditioning system. “You can see the white tubes go up along the outside of the house, and then they go through the wall into where the various inside units are.”

In other words, it looks like the outside component of a central air conditioner, but it hums in the dead of winter too.

“It’s an air conditioning unit that can run in reverse and make heat too,” said Christian Agulles, a mechanical engineer and president of a clean energy firm called PAE Engineers. “Its job is to take heat from the inside and reject it outside.”

In the winter, it just does the reverse. And even when it’s subfreezing outside, there is still heat that can get pumped into the house. Constant technical improvements enable heat pumps to extract heat from colder and colder air. Agulles said they’re effective down to 10 or 15 degrees below zero Fahrenheit. 

They run on electricity, which can come from renewables, and they’re two to four times more efficient than, say, a gas furnace.

“Gas furnaces generate heat, and heat pumps transfer heat,” Agulles said. And moving something takes less energy than making something.

Heat pumps have taken off in Maine because gas furnaces aren’t a great option there. Utilities didn’t see much point in installing lots of gas pipelines for the state’s spread-out population. Instead, Maine depends on home heating oil more than any other state. And that stuff is not cheap.

Right before Wilcox decided to install his heat pump, he got an eye-watering bill from his heating oil company. “For $1,320,” Wilcox said. “And you can have to refill two to three times during the winter. And so that was the wake-up call for us.”

Mainers are installing heat pumps three times faster than the national average. 

But outside the northeastern heat pump haven, wherever natural gas is more popular, the number of heat pumps shipped in the U.S. went down last year. There’s a reason for that, said Agulles.

“In some parts of the country, electricity is five times more expensive than natural gas,” Agulles said. He lives in Northern California, home to some of the highest electric bills in the country. “At four times more efficient, it’s still more expensive to run if your electricity rate is really high.”

The other problem: Even when a homeowner is interested in investigating whether a heat pump might make sense, if it’s February and the boiler goes out, “that’s an emergency, and they’re not going to have the time to do the research on heat pumps,” said Ethan Elkind with the Center for Law, Energy and the Environment at the University of California, Berkeley.

Elkind said the contractor who comes to save the day might not even know how to install a heat pump.

“Then people aren’t going to demand to get a heat pump, and then they’re not going to see the demand encourage more contractors to start selling heat pumps,” Elkind said.

Federal and state incentives promise thousands of dollars to homeowners who are willing to switch to heat pumps, unless President-elect Donald Trump makes good on his promise to claw back that funding.