Does a Heat Pump Actually Work in Cold Weather?
This is probably the most common question homeowners have when they’re considering a heat pump. The short answer: yes, modern heat pumps work in cold weather — and they work better than most people expect.
The Basic Principle
A heat pump doesn’t generate heat the way a furnace does. Instead, it moves heat from one place to another. In winter, it pulls heat energy from the outdoor air and transfers it inside. Even when it’s 20°F outside, there’s still usable heat energy in the air — the pump just has to work harder to extract it.
What “Balance Point” Means
Every heat pump has a balance point — the outdoor temperature at which the system can no longer keep up with demand on its own. For older heat pumps, that used to be around 35–40°F. Modern cold-climate heat pumps (look for the NEEP-listed cold-climate models) can operate efficiently down to 0°F or below.
Auxiliary and Emergency Heat
Most heat pump systems include a backup — usually electric resistance strips — that kicks in when it’s extremely cold or when the heat pump needs help meeting the set temperature. This is called auxiliary heat (aux heat) and it’s normal. Emergency heat mode bypasses the pump entirely and runs only the backup strips; it costs significantly more to operate and should only be used if the heat pump itself is broken.
Defrost Cycles
In cold, humid weather, the outdoor unit can ice up. Heat pumps handle this automatically through a defrost cycle — the system briefly reverses direction to melt the ice. You may notice steam rising from the outdoor unit during this cycle. That’s normal. If the unit is heavily iced over for hours and not clearing, that’s a problem worth calling a tech about.
Should You Get One?
If you’re in a climate that dips below 15°F regularly, look specifically at cold-climate models. In most of the US, a modern heat pump is an efficient, capable primary heating system — not just a shoulder-season solution.