How does a heat pump work in winter?
It seems backwards to pull heat from cold air — but that is exactly what a heat pump does. Here is how winter heating works.
Pulling heat from cold air
Even air at 20°F contains plenty of heat energy (heat exists down to −460°F). A heat pump's refrigerant boils at a very low temperature, so it can absorb heat from cold outdoor air, and the compressor then concentrates that heat to a warm temperature for your home. The colder it gets, the less heat is available, so output gradually drops — but it keeps working far below freezing.
Defrost cycles and backup heat
In cold, damp weather, frost forms on the outdoor coil, so the heat pump runs a brief defrost cycle (it steams and blows cool air for a few minutes). When it is too cold for the heat pump to keep up — below the balance point — auxiliary heat (electric strips or a gas furnace in a dual-fuel system) assists automatically.
Cold-climate models change the game
Cold-climate (hyper-heat) heat pumps use variable-speed compressors to hold capacity at low temperatures, heating efficiently to −13°F or lower and pushing the balance point well down — so they rely on backup heat far less. In harsh winters, a cold-climate model (or a dual-fuel system) is the right choice.
Frequently asked questions
How does a heat pump heat a house in winter?
It absorbs heat from outdoor air using a low-boiling-point refrigerant, then the compressor concentrates that heat to warm your home. Even cold air holds usable heat.
Do heat pumps work when it is freezing?
Yes — they keep heating below freezing. Output drops as it gets colder, and below the balance point backup heat assists. Cold-climate models work efficiently to −13°F or lower.
Why does my heat pump blow cold air in winter?
Usually a normal defrost cycle (a few minutes) melting frost off the outdoor coil. Persistent cold air points to a fault.
Related
Sources & further reading
Educational guide, reviewed against US DOE & ENERGY STAR guidance and updated June 2026. Estimates only — not a substitute for a professional assessment or Manual J load calculation.