#cold climate

"Heat pumps don't work in the cold" is the objection every HVAC tech hears at the kitchen table. In 2023, researchers put it up against field data from roughly 550 installed heat pumps and 2,760+ real-world measurements, pulled from seven field studies across Europe, North America, and Asia. The objection lost.

The numbers, published in the journal Joule by Duncan Gibb, Jan Rosenow, Richard Lowes, and Neil Hewitt: between 41°F and 14°F, air-source heat pumps averaged a COP around 2.7. That means 2.7 units of heat delivered for every unit of electricity consumed. Electric resistance heat manages exactly 1, always.

Even on the coldest days in the studies, standard units held a COP near 2. Cold-climate models tested in extreme conditions stayed between 1.3 and 2 heading toward -22°F. Against oil and gas, heat pumps ran two to three times more efficient between 32°F and 5°F, and still about 1.5 times more efficient near -22°F.

The kicker: Canadian installs averaged a COP of 3.3 in the moderate-cold band, the best of any country in the dataset. Harsh winters, strong numbers. Proper sizing and commissioning do a lot of work.

The old reputation came from somewhere real. Single-speed builder-grade units from the 1990s did fall apart below freezing. Inverter compressors, vapor injection, and better defrost logic changed that, and this field data shows what current equipment actually does in occupied homes through real winters.

One honest caveat from the authors: in climates regularly below about 14°F, supplemental heat can still make sense, since heating demand rises as capacity drops. That's a load-calculation question, not a dealbreaker. A unit sized properly against the local design temperature behaves the way this data says it should; a unit sized off a square-footage rule of thumb is the one that ends up feeding the myth.

The paper: Gibb et al., Joule 7(9), 2023.

Two-stage R-290 heat pump: 18.3% more heating capacity at -8.3°C.

Purdue built a variable-speed two-stage propane (R-290) liquid-to-liquid heat pump with independent compressor control. Published in Applied Thermal Engineering 2025.

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Winter can be brutal, even for some of the strongest animals in the wild. Understanding how big cats and bears survive winter reveals their extraordinary adaptations to freezing temperatures and scarce food. Big cats like Siberian tigers, snow leopards, and mountain lions endure the cold by growing thick, insulating fur that traps heat and protects them from icy winds. Additionally, they build up fat reserves before winter, providing much-needed energy when prey becomes scarce. Seeking shelter in caves, dense vegetation, or lower elevations also helps them escape the worst of the winter chill.

This Norwegian man saw his electricity bills shrink after replacing his radiator with a heat pump. Oyvind Solsta’s “light bulb” moment with heat pumps came upon reading that the heat they produce far exceeds the amount of electricity that goes in. Installing a heat pump in his house in the hills of Oslo has greatly benefited the 56-year-old communications adviser for a railways company: improving his comfort, finances and climate footprint. Norway is among the countries with the most heat pumps per capita, along with neighbouring Finland and Sweden. "When I researched this, I read that a heat pump can generate the heat equivalent of three to four times the amount of electricity you put into it," said Solsta. "So just that fact made a light bulb go off above my head, thinking 'This has to be clever'." Hundreds of thousands of Norwegians have had the same bright idea, including Crown Prince Haakon who has had heat pumps installed at his official residence. The International Energy Agency (IEA) considers the technology as instrumental in combatting climate change as electric vehicles, since heating solutions generate some four billion tonnes of carbon dioxide per year, representing eight per cent of global emissions.