Home › Weather › How Do Heat Pumps Work In Cold Weather
Live forecasts update automatically; written guidance last reviewed 16 June 2026 by the Canada Scene Weather Desk. Data from Environment and Climate Change Canada and other national met services via Open-Meteo.
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Heat pumps work in cold weather by extracting ambient heat from the outdoor air—even when temperatures drop well below freezing—and compressing it to warm your home. They remain efficient down to about -15°C to -25°C, depending on the model, making them a viable heating option for many Canadian climates.
How does a heat pump keep producing heat when it’s freezing outside?
Refrigerant in the outdoor coil absorbs heat from the air, even at -20°C. An electric compressor then pressurizes that refrigerant, raising its temperature dramatically. A reversing valve sends the hot gas indoors, where a fan blows across the indoor coil to release heat into your living space. Newer cold-climate models use variable-speed compressors and enhanced vapour injection to maintain output in extreme cold.
When should I rely on backup heat in Canada?
Once temperatures fall below your heat pump’s rated design temperature (check the manufacturer’s spec), the system will automatically switch to auxiliary electric resistance heating or a gas furnace, if installed. This dual-fuel setup is common in Prairie provinces where winter lows can hit -40°C. The live forecast above can help you decide when to let backup take over.
Does a heat pump cost less to run than a furnace in Canadian winters?
Yes, in milder spells. Above -10°C, a heat pump often costs half as much as electric baseboard. But below -20°C, a gas furnace or electric backup may be cheaper per unit of heat, depending on local electricity and gas rates.
Should I worry about frost building up on the outdoor unit?
No—the unit periodically runs a defrost cycle (reversing the system briefly to melt ice). You’ll see steam or water dripping; that’s normal. Keep snow drifts cleared away from the unit’s intake and exhaust for proper airflow.
Can I install a heat pump in my old Toronto home?
Most likely, yes. Ducted homes can swap out an existing central air conditioner for a cold-climate heat pump. Ductless mini-split systems work well in older buildings without ductwork. Check rebates and see our Toronto weather page for seasonal planning.