Heat pumps—heating and cooling systems that run entirely on electricity—have received a lot of attention lately. They’ve been dubbed “the most overlooked climate solution” and “the heatwave solution.” The technology has finally caught on globally. last year, 117 million units 90 million units were installed worldwide in 2010. As temperatures and greenhouse gas emissions rise, heat pumps can easily be powered by renewable energy, promising a pathway to carbon-free home heating. Environmental activist Bill McKibben has even suggested sending heat pumps to Europe to help the continent wean itself off Russian gas.

But despite the surge in popularity of heat pumps around the world, U.S. heat pumps struggle with a misconception that has plagued them for decades: If the temperature drops below 30 or even 40 degrees Fahrenheit, their technology simply won’t work. “Do heat pumps work in cold weather” is even a trending question on Google.

Andy Meyer, senior program manager at Efficiency Maine, an independent state agency, has spent the past decade debunking that claim for residents of one of America’s coldest states.

“There were two kinds of people in Maine in 2012,” he said. “Those who don’t know what a heat pump is — and those who know they can’t work in the cold.” But while that concern might have been true a few years ago, he said, today “for high-performance heat pumps Not at all.”

Air source heat pumps – also geothermal heat pumps and water source heat pumps – are poorly named and poorly understood. (About 47% of homeowners in the Northeast have never heard of heat pumps, according to a small 2020 study by heating technology company Sealed.) They’re essentially reversible air conditioners: like air conditioning units, they can operate from The interior of the air conditioner captures heat. Go home and pump it out to provide a cooling effect. But unlike air conditioners, they can also work in reverse — taking heat from outside and bringing it inside to warm the home.

that process move hot instead​​ create It explains why heat pumps are surprisingly efficient. Gas furnaces that burn natural gas to generate heat are only about 95 percent efficient. A heat pump can easily be 300% or 400% efficient; that is, it can produce about 3 to 4 times as much energy as it consumes.

A worker installs a heat pump at his home in Standish, Maine, in 2018.
Brianna Soukup/Portland The Portland Press Herald via Getty Images

Years ago, the technology actually only worked in mild climates. Early heat pumps were mostly installed in southern states that needed air conditioning and just a little extra warmth in winter. “They’re really gaining traction in areas that aren’t cold,” said Ben Schoenbauer, a senior research engineer at the Minnesota Center for Energy and the Environment (CEE).

But over the past decade or so, heating companies have begun developing a new generation of heat pumps with “inverter-driven variable-speed compressors” — a term that essentially allows heat pumps to deliver warmer air from the cold outside more quickly .

Soon, high-performance heat pumps were produced that could warm homes even when the outside temperature dropped to -31 degrees Fahrenheit. (even at extreme sub-zero temperatures, there are still Some heat in the outdoor air. ) The efficiency of a heat pump does drop as the temperature decreases, but even in sub-zero temperatures high-end units can be more than 100% efficient. Some of the coldest states in the country have gone all-in on the technology in recent years. According to a study in Environmental Research Letters, heat pumps could reduce carbon dioxide emissions in 70 percent of households nationwide; households heated by inefficient electric heaters or oil may particularly benefit. Utilities and states have started offering rebates for consumers to install heat pumps, even in cooler states like New York, Massachusetts or Maine. Many environmental groups and state agencies are working to convince residents that top-of-the-line heat pumps can work well in colder climates.

Efficiency Maine has been part of this trend. In the early days, residents were deeply skeptical that a simple electric device could stay warm in the state’s frigid conditions, Meyer said. But Efficiency Maine recruited installers, ran social media and radio ads, and published studies and reports showing that heat pumps could work. “It started in northern Maine — a very tight, tight-knit community,” Meyer said. Once some people have a heat pump installed, they start telling their friends, who tells their friends, and so on. So far, Efficiency Maine has offered rebates for 100,000 heat pumps — fewer than 600,000 residential units in the state, Meyer said. Maine now has a higher per capita heat pump installation rate than most European countries.

Other organizations are doing similar work. The Minnesota Energy and Environment Center has partnered with utilities to help increase heat pump adoption in the state; they also maintain a vetted list of contractors who can install the system. The Massachusetts-based nonprofit Northeast Energy Efficiency Partnerships provides resources for installers and consumers, including a list of air source heat pumps that work well in Northeast states’ climates. Alaska even has some heat pumps installed, where average winter temperatures hover around 23 degrees Fahrenheit.

One of the benefits of installing a heat pump is cost savings. In Maine, many homes use oil or propane for heating. At current prices, running a heat pump would cost half as much as oil and one-third as much as propane, Meyer said. According to an analysis by Efficiency Maine, this can save homeowners up to thousands of dollars in annual energy costs. A 2017 CEE study similarly found that installing a heat pump in Minnesota could save residents $349 to $764 per year compared to heating with a standard electric or propane furnace.

There are some caveats. Lacey Tan, project manager for carbon-free buildings at energy think tank RMI, said there was still a premium on the price of heat pumps: some installers were not satisfied with the way they worked and tried to reduce the risk by adding heat pumps. -Initial expenses. In cold climates, some homes may wish to have a backup heating system on extremely cold days or in the event of a power outage. (In Maine, Meyer says many homeowners use wood stoves as backup to heat pumps.)

But many experts believe that more and more cold-weather heat pumps will be sold as homeowners learn about new advances in the technology. Meyer said Mainers who installed heat pumps naturally started sharing their experiences with friends and family. “We’ve got over 100,000 salespeople already getting heat pumps,” he jokes. “Not bad for states where they ‘don’t work in the cold.'”