Heat pumps – heating and cooling systems that run entirely on electricity – have gotten a lot of attention recently. They have been called “the most neglected climate solution” and “a response to heat waves.” And the technology is finally experiencing a global boom in popularity. Last year, 117 million units installed worldwide, up from 90 million in 2010. As temperatures and greenhouse gas emissions rise, heat pumps, which can easily be powered by renewable energy, promise to provide a path to carbon-free home heating. Environmental activist Bill McKibben even proposed the mission heat pumps in Europe to help wean the continent off Russian gas.
But despite a global surge in popularity, heat pumps in the U.S. labor under a misconception that has plagued them for decades: that if the temperature drops below 30 or even 40 degrees Fahrenheit, their technology simply won't work . “Heat pumps work in cold weather” is still a modern question on Google.
It's a narrative that Andy Meyer, senior program director for the independent state agency Efficiency Maine, has spent the past decade debunking for residents in one of the coldest states in the US.
“There were two types of people in Maine in 2012,” he said. “Those who didn't know what heat pumps were — and those who did didn't work in the cold.” But while that concern might have been true years ago, he said, today “it's not true at all for high-efficiency heat pumps.”
Air source heat pumps — there are also geothermal heat pumps and water source heat pumps — are poorly named and poorly understood. (According a small study of 2020 (from heating technology company Sealed, about 47 percent of homeowners in the Northeast U.S. hadn't even heard of heat pumps.) They're essentially reversible air conditioners: Like AC units, they can take heat from inside a home and pump it to provide a cooling effect. But unlike air conditioners, they can also work backwards — drawing heat from outdoors and bringing it inside to warm a home.
This process of movement heat than creating explains why heat pumps are surprisingly efficient. A gas furnace — which burns natural gas to create heat — can reach about 95 percent efficiency. A heat pump can easily reach 300 or 400 percent efficiency; that is, it can make about 3 to 4 times more energy than it consumes.
Brianna Soukup/Portland Portland Press Herald via Getty Images
Years ago, the technology only really worked in mild climates. The early generation of heat pumps were mostly installed in southern states that needed air conditioning and a little extra warmth in the winter. “They really gained traction in areas where it wasn't cold,” said Ben Schoenbauer, a senior research engineer at the Center for Energy and Environment, or CEE, in Minnesota.
However, in the last decade or so, heating companies have begun to develop a new generation of heat pumps with “variable speed inverter compressors” – a mouthful of a term that essentially gives the heat pump the ability to transfer heat more quickly from cold outdoor air.
Soon, high-efficiency heat pumps were created that could heat a home even when outside temperatures were below -31 degrees Fahrenheit. (Even in extreme sub-zero temperatures, it's still there some amount of heat to the outside air.) A heat pump's efficiency decreases as it cools, but even in sub-zero temperatures high-end units can be out 100 percent effective. And in recent years, some of the coldest states in the country have gone all-in on technology. According a study In Environmental Research Letters, heat pumps could reduce CO2 emissions in 70 percent of homes across the country. Homes heated with inefficient electric heaters or fuel oil could benefit especially. Utilities and states have begun offering rebates to consumers for installing heat pumps, even in colder states like New York, Massachusetts or Maine. Many environmental groups and government agencies are working hard to convince residents that top-of-the-line heat pumps can work well in cold climates.
Efficiency Maine was part of that trend. Early on, Meyer said, residents were deeply skeptical that a simple electrical appliance could keep them warm in the state's frigid conditions. But Efficiency Maine hired installers, ran social media and radio ads, and published studies and reports showing heat pumps could work. “It started in Northern Maine — a very close-knit, tight-knit community,” Meyer said. Once a few people installed heat pumps, they started telling their friends, who told their friends, etc. So far, Meyer says, Efficiency Maine has offered rebates for 100,000 heat pumps — in a state with fewer than 600,000 occupied homes. Maine now has a higher rate of heat pump installations per capita than most European countries.
Other organizations do similar work. The Minnesota Center for Energy and Environment has formed a partnership with utilities to help boost heat pump adoption in the state. They also maintain a list of contractors who have been vetted to install the systems. The Northeast Energy Efficiency Partnerships, a Massachusetts-based nonprofit, has resources for installers and consumers, including a list of air-source heat pumps that work well in Northeast climates. Some heat pumps are even installed Alaskawhere average winter temperatures hover around 23 degrees Fahrenheit.
One of the benefits of installing heat pumps is cost savings. In Maine, many homes are heated with fuel oil or propane. At current prices, Meyer says, a heat pump costs half as much to run as oil and one-third as much as propane. According to Efficiency Maine's analysis, this can save homeowners up to thousands of dollars in the annual energy cost. ONE 2017 study by CEE similarly found that installing heat pumps in Minnesota could save residents between $349 and $764 annually, compared to heating with a typical electric or propane furnace.
There are some caveats. Lacey Tan, director for the carbon-free buildings program at energy think tank RMI, says there's still a price premium for heat pumps: Some installers aren't yet comfortable with how they work and are trying to reduce risk by increasing – up-front costs . In cold climates, some homes may want to have a backup heating system for extremely cold days or in the event of a power outage. (In Maine, Meyer says many homeowners use wood stoves as backups to their heat pumps.)
But many experts believe that more and more cold-weather heat pumps will be sold as homeowners learn about new advances in technology. Meyer says Mainers who install heat pumps naturally start sharing their experience with friends and family. “We have over 100,000 sellers who have already taken heat pumps,” he joked. Not bad for a state where “they don't work in the cold”.
