According to a recent study published in Joule, heat pumps aren’t just capable of functioning in freezing temperatures. They actually outperform fossil fuel heating systems in cold climates.

Heat pumps, which both heat and cool indoor spaces, move warmth in and out as needed. Despite experiencing an 11 percent growth in global sales in 2022, they only represent a small fraction of the world’s building heating.

To achieve the net-zero emissions target of the Paris Agreement by 2050, heat pumps will need to replace a significant number of gas boilers and furnaces, even in regions with extremely cold winters.

Utilities and fossil fuel interests claim that heat pumps are ineffective in sub-freezing temperatures. However, recent studies have proven that this just isn’t true.

The Joule study

To evaluate the performance of air-source heat pumps in plummeting temperatures, the research team analyzed data from seven field studies conducted across Canada, China, Germany, Switzerland, the United Kingdom, and the United States.

These studies focused on heat pump performance during January, using a metric known as the coefficient of performance (COP). This metric measures the amount of thermal energy produced by a heating system for every unit of energy input.

Heating technologies that use fossil fuels have a COP of 1, as they convert one form of energy into another. On the other hand, heat pumps use refrigerant to cleverly transfer heat. This means that they can achieve COPs ranging from 3 to 4, even reaching as high as 7 in some cases.

Efficiency decreases when temperatures drop. However, this occurs due to the widening difference between outdoor and desired indoor temperature. This is why geothermal heat pumps, which draw heat from the earth and are more insulated from temperature swings in the ambient air, are considered more efficient.

Although the coefficient of performance (COP) of air-source heat pumps decreases in colder temperatures, heat pumps beat gas furnaces even in extreme cold weather.

On average, heat pumps remain twice as efficient as gas furnaces at -13°C. Specially designed cold-climate heat pumps can produce heat in even more extreme weather. COPs of 1.5 or higher have been recorded in Finland at temperatures as low as -30°C (-22°F).

Heat pumps gain ground in cold climates

Heat pumps are gaining popularity in colder regions like Scandinavia due to their ability to withstand frosty winters. In fact, Norway, Sweden, and Finland have recorded the highest per capita sales of heat pumps in Europe.

The United States has also shown success in heat pump adoption. According to Canary Media, US heat pump sales surpassed gas furnace sales last year.

Maine is one of America’s coldest states. It has already surpassed its goal of installing 100,000 new heat pumps by 2025 and has now set a new target of 175,000 more by 2027. Maine residents have testified to the effectiveness of heat pumps in keeping them warm even during extreme cold weather.

Fossil fuel companies often use minor declines in heat pump efficiency as a justification to delay the transition to clean heat. For instance, US utility company Xcel Energy has argued for a limited role for heat pumps in Colorado, citing a report it funded. The report highlighted a 5 to 12 percent decrease in heat pump efficiency at lower temperatures.

It’s indeed accurate that heat pump performance decreases in colder temperatures. However, disregarding heat pumps based on this reality is overlooking the technology’s reliable and efficient functioning in cold weather, which surpasses that of fossil-based alternatives.

Image Source: Jon Burke,