Here’s something you realize pretty quickly when you begin reporting a piece about heat pumps: the people who are enthusiastic about them are extremely enthusiastic.

In the last few years, these humble bits of home infrastructure have become downright buzzy for both their efficiency and sustainability bona fides. States are rolling out incentives to encourage installations, as well as training programs to get more installers working. It’s a major priority for the climate movement, and the tech featured heavily in the Inflation Reduction Act. A coalition of 25 state governors recently announced a push to quadruple the number of heat pumps installed by 2030, bringing the number to 20 million; the New York City Housing Authority is turning to the technology in an effort to upgrade its aging, troubled infrastructure. And consumers are embracing it, too: Maine recently announced it had blown past its goal of installing 100,000 new heat pumps by 2025, two years early. And if a heating technology works in Maine, it works—heat pumps have improved significantly in recent years. If your notion of the technology is from sometime in the late ’70s, it’s out of date.

The 1990 movie Home Alone did a pretty good job of capturing the overall vibe between homeowners and the basement furnace—it’s big, hulking, and scary. Not because you’re a kid and it has a creepy anthropomorphic face, but because if it fails, it’ll inevitably be on a day of record low temperatures, which is somehow also Thanksgiving, and it’ll cost $15,000 to replace, and every minute you use it to warm your house, you’re burning both carbon and money. (So much money.)

So here’s what you need to know if you’re considering making the switch, or even if you’re building from the ground up.

So, what exactly is a heat pump?

The essential thing to understand about heat pumps is that they’re a source of heating and cooling that doesn’t generate heat—they transfer it.

“Heat naturally travels to where it’s cold,” says Matthew Scott, Vice President at Maine-based Dave’s World Heating and Cooling, laying out the explanation he’s perfected over many years of explaining the technology to customers. The temperature where no heat exists isn’t zero degrees Fahrenheit—it’s absolute zero, or -460 degrees Fahrenheit. “If you are at -20 or -30 or -40 or -200 or -300, there’s still a lot of heat out there. You don’t think so, because you’re a human and you’re 98.6 degrees. But you’re not the test strip for if there’s heat out there.”

Whereas a traditional furnace burns oil to generate heat, a heat pump uses refrigerant coils (in pipes that sit on the exterior of your home) to make itself colder than the temperature outside, pulling the heat inside and distributing it through a box that looks a bit like a mini-split air conditioner. At that point, you’ve essentially “tricked and trapped that heat outside, and you brought it inside without ever lighting anything inside,” says Smith. It works in reverse, too, which means it does double duty as an air conditioner.

What’s the argument for heat pumps?

That heat transfer (rather than generation) means that heat pumps are incredibly efficient machines. It also makes it very straightforward to zone off various parts of your house, heating the living room on a Tuesday night without wasting oil on the dusty guest room. So while the initial investment isn’t cheap—Scott ballparked $15,000 for a new furnace, versus $20,000 for a heat pump system, it almost certainly means lower energy costs, especially if you live in a place that requires heating a good chunk of the year. (In some markets, natural gas may be cheaper, but it’s definitely a savings over the oil-burning furnace.)

A lot of talk about heat pumps emphasizes efficiency and the possible energy savings. Scott, however, also emphasizes the sheer luxury of the air conditioning aspect. Plus it makes the technology effectively a two-for-one deal, especially if you’re retrofitting an older house that doesn’t have central AC.

What’s the sustainability case for heat pumps?

“Heat pumps are a top-tier priority for the climate movement, for climate change mitigation in the built environment,” explains Amanda Sachs, a policy analyst at the pro-electrification nonprofit Rewiring America. That’s because they’re both extremely efficient, and powered by electricity, “which over time has become increasingly renewable and clean.”

“The heat pump can replace the most carbon-intensive machines in your home, which are space and water heating,” Sachs says. Even if the grid you are connected to is not fully renewable, because heat pumps are more efficient and require less energy, you are lowering your carbon emissions by 55 to 76 percent.

“Buildings are contributing so much to climate change–in the U.S. it’s second only to transportation but in some states it’s the number one contributor to climate change,” she says. To hit climate goals, we need to find straightforward ways to decarbonize quickly. And heat pumps very much are: “This is a relatively cheap way to go about it, it’s straightforward, we know exactly what we need to do, we have the technology.”

Sachs stresses that big decisions do matter, for climate purposes: “Your car purchase, your appliance purchases, what you use to heat your home—those are the decisions that really matter, more so than do I use a Keurig or a French press.” What you’re going to do when your furnace is on its last legs is one of those decisions.

What do I need to know?

One of the biggest questions people tend to have once you get past the basic idea, in Scott’s experience: aesthetics. “Where is it going to go, and what’s it going to look like?” Scott says. “It’s funny because a lot of people, they’re like, you’re going to put that big white thing up on the wall? And I’m like, what about the hair-clogged, dented baseboard that goes all around the room?”

“I get it—running pipe up the side of your house, no matter how decorative it is, it looks different.”

But the installation process for heat pumps is fairly straightforward. “We’re usually in and out of your house in a day, maybe two, maybe three if you’re doing most of the home,” he explains. “Worst case scenario, three days, and you can’t see the construction other than these things that look like they grew out of your walls.”

Heat pump systems work in zones; on average, most of the jobs for Dave’s World are three-zone: “One in the bedroom, one in the great room, and one in either the spare, or that great room is taking two units because it’s big, the kitchen and the living room’s connected.” Some people do entire sprawling homes with five or seven zones; you could call up an installer and ask them to do just a single-zone pump in the three-season room you frantically turned into an office at the height of the pandemic.

You don’t necessarily pull out the furnace entirely, either. It’s possible to install heat pumps and leave a traditional system as a backup for the absolute coldest days of the year.

The trickiest aspect is getting the right equipment for your house and your particular climate; there’s an extremely wide variety of models on the market. And that requires getting a contractor with enough expertise, Scott cautions: “I think the biggest red flag is when they don’t do math in front of you,” mapping out your space and how many BTUs you’ll need for it and tailoring their suggestions accordingly.

What incentives are available?

Scott was straightforward about the fact that heat pumps aren’t cheap: “They’re expensive. They are the most expensive heating and cooling device out there, but there’s a reason for it,” he says, citing the efficiency over time and the fact it’s effectively a two-for-one deal, offering both heating and cooling (an attractive proposition in places with high heating bills and, traditionally, no air conditioning).

However, there are a variety of tax credits on the federal, state, and local level. The aforementioned Inflation Reduction Act, for instance, offers a $2,000 tax credit on a heat pump. “It’s not exactly going to make it as cheap as getting a replacement furnace, but we’re trying to make it comparable,” says Sachs. “And then over time, you see a lot of cost savings in your utility bills.” That’s because the machines are so efficient—besides being good for the climate, it saves money. Rewiring America has created a calculator to help navigate the process of figuring out what incentives are available to you, as well as a consumer site with resources about how to start the electrification process. Many states also have their own sites full of resources. Maine, for instance, has Efficiency Maine, which has a great deal of information about installation and a database of licensed contractors.

Both Sachs and Scott say there’s no reason to wait for the technology or the current incentives to improve. “It’s not going to get much better. It can’t,” Scott explains. ”We’re getting heat out of -20 degree air here, very efficiently. Don’t wait for the one that goes down to -30, because that happens once every ten years.” And if you wait five years, he adds, “the one you should have put in would have already paid for itself.”

Illustration by Mar Hernández

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