Do heat pumps work in cold climates?

Heat pumps work even in very, very cold weather. Thanks to technological advancements in recent decades, heat pumps keep your home toasty warm even when the temperature drops dramatically. In fact, eight of the major heat pump companies — Bosch, Carrier, Daikin, Johnson Controls, Lennox, Midea, Rheem, and Trane Technologies — have successfully tested their cold climate heat pumps with the Department of Energy in sub-zero temperatures. Some units continued performing at temperatures as low as –15 degrees Fahrenheit! 

Still skeptical? Heat pumps heat roughly half the homes in snowy Norway, Finland, and Sweden, and more than 115,000 heat pumps have been installed in Maine, one of the coldest U.S. states. (As they say, if you’re an HVAC system that can make it in Maine, you can make it anywhere.)

Despite the facts, many contractors and homeowners still think heat pumps don’t work well in very cold climates. Why? Three big myths are to blame:

Three myths about heat p ump operation in subzero temps

1. The capacity myth, which argues that heat pumps can’t produce enough heat to keep your home comfortable in cold weather. 

2. The efficiency myth, which argues that heat pumps dramatically lose their efficiency advantage when the temperature drops. 

3. The money myth, which argues that due to their lower efficiency in cold weather, heat pumps burn up your money in the winter.

To be fair, there are seeds of truth in these myths. If a heat pump is not sized properly, it will absolutely fail to meet a home’s heating and cooling needs. And in some cold climate areas where the utility rates (or the relative cost of fossil fuels compared to electricity) keep methane gas cheap, heat pumps cost more to operate, despite being much more efficient.

So, how can you be sure that your heat pump will keep you warm? Let’s get to the bottom of that question and provide some clarity. But first, let’s remember how heat pumps work in the winter.

In heating mode, heat pumps go into reverse and pump heat from the air outside your home to the inside. How does that work? Because heat is energy, there’s energy in the air even when it’s very cold outside. Believe it or not, super cold air — 0 degree Fahrenheit — contains more than 75 percent of the energy in 140 degrees Fahrenheit air! 

Back in our grandparents’ day, heat pumps couldn’t handle cold climates. But now, thanks to some major technological advancements, heat pumps perform beautifully in the coldest parts of the world. As Consumer Reports writes, heat pumps “can keep your home toasty even amid bone-chilling cold, using far less energy than other types of heating systems.”

With all that in mind, let’s start mythbusting.

The capacity myth

The first myth to debunk is “the capacity myth” which is the notion that heat pumps don’t have enough capacity to keep a home warm on a cold day. 

For the vast majority of people in America, heat pumps can supply 100 percent of the capacity necessary to keep their homes comfortable all year round. And if your heat pump is accurately sized, it will meet your needs year-round, even if its efficiency decreases when it’s colder. 

Earlier we mentioned two terms: load and capacity. To understand why the capacity myth isn’t true, it’s helpful to understand these two concepts.

The heating load of a home is the amount of energy required to keep it at the comfortable temperature you set your thermostat at. As the temperature changes, the load changes. On a nice, 70 degree Fahrenheit day, the load is basically zero. On a freezing cold day it’s much higher; your heating system simply needs to work harder to meet the load and keep your home comfortable.

The load also depends on unique characteristics of the home like the amount of insulation or the type of windows and doors. A home built in 1850 with no insulation requires more energy than a brand new home built following new codes and standards. The load is just a technical way to describe and measure all of this heat transfer in and out of the building. 

The capacity is the amount of heat — or, in the case of air conditioning, cold — that a HVAC system can supply to meet the load. If load is the leak at the bottom of your bucket, capacity is the faucet bringing in more water. 

Heat pumps are unique compared to every other HVAC system in that they don’t have a single fixed capacity. Since they use the energy in the air to heat and cool your home, the capacity of most residential heat pumps (called air source heat pumps) is a function of the outdoor air temperature. The capacity of ground source heat pumps remains intact with changes in outdoor air temperature as the upper 10 feet of the Earth maintains a temperature between 50-60 degrees Fahrenheit. The lower the temperature drops, the less energy there is to move. This is why in extremely cold environments, your contractor will recommend a cold climate air-source heat pump — which generates tons of heat from very cold air while retaining much of their capacity — to heat your home in sub-zero conditions.

The efficiency myth

The magic of a heat pump is that it uses one unit of energy (electricity) to transfer 2-5 units of energy (heat) from one area to another. But this ratio – referred to as the coefficient of performance (COP) – isn’t a fixed number all the time. 

The colder it is outside, the harder it is for a heat pump to effectively transfer heat from outside air into your home. Hence, the lower the outdoor temperature gets, the efficiency of the heat pump (presented as COP) drops. 

Compared to the heat pumps of yesteryear, today’s cold-climate heat pumps achieve a COP of at least 1.75 at 5 degrees Fahrenheit. At 30 or 40 degrees Fahrenheit, many of them achieve COPs ranging from two to three. 

The takeaway? Today’s heat pumps are the most energy efficient way to heat and cool a home even in extremely cold weather. 

The money myth

In America, energy prices vary widely depending on where you live. In Connecticut, electricity costs a little more than $0.20 per kWh. Those same electrons cost $0.10 per kWh in Louisiana. 

Natural gas has a similarly large range. One therms equals 100,000 BTU and in Florida the average price of residential natural gas is about $2/therm. In Idaho it’s $0.65/therm. In addition to that, every climate and home is different. Each one requires a different amount of energy to stay warm in the winter. 

In 2024, the National Renewable Energy Laboratory (NREL) announced that 65 million American households, including those in cold climates, could save on energy bills (without subsidies) by switching to air-source heat pumps. If you spend a lot of money heating your home every year, the odds are pretty good that a heat pump is going to save you money whether you live in Florida or Maine. And if you currently heat your home with a standard electric unit, fuel oil, or propane, there’s almost no doubt that you can save money. 

Over time, we can expect these savings to grow. In the near future, many energy analysts expect natural gas prices to go up and electricity prices to go down as governments begin pricing carbon pollution and utilities build massive amounts of cheap renewable electricity. Meanwhile, heat pumps keep getting more efficient, compared to alternatives like gas furnaces and electric resistance systems, which have already reached their theoretical maximum efficiency.

The bottom line: selecting the right model and properly sizing your heat pump will keep you warm all year round!