Do heat pumps work in cold climates?

A heat pump collects heat from outdoor air. Cold air still holds heat, but there is less of it to collect, and the system has to work harder to move it indoors. Two things happen as the temperature drops: the heat pump's output falls, and your house needs more heat. At some outdoor temperature those two lines cross. Below that point the heat pump cannot carry the house alone and backup heat fills the gap.

Frost is the other winter factor. The outdoor coil frosts over in cold, damp weather, and the system runs short defrost cycles to clear it. That is normal operation.

ENERGY STAR describes newer cold-climate models as using advanced compressors and refrigerants to perform better at low temperatures. To earn its cold-climate designation, a model needs third-party verified performance at low temperatures, with testing down to 5°F. Below that temperature the unit keeps running, and ENERGY STAR notes that a backup heat source is the most efficient choice when temperatures drop even lower.

In practice the main differences are:

• Variable-speed compressor. It speeds up in the cold to hold output and slows down in mild weather.
• Rated low-temperature capacity. The manufacturer publishes how much heat the unit delivers at low outdoor temperatures, so the installer can size against your winter design conditions.
• Smarter defrost. Controls that defrost only when needed.

This page does not rank brands or models. Ask installers for the certified low-temperature ratings of whatever they propose, and compare those.

A heat pump fits a cold climate when three things line up:

1. The model is rated for your winter. Check its capacity at the low temperatures your area actually sees, as well as at mild conditions.
2. The size comes from a heating load calculation. ENERGY STAR advises verifying size with a Manual J calculation. In cold regions the heating load, more than the cooling load, tends to drive the size.
3. The backup is planned. Electric strips, a gas furnace in a dual fuel setup, or another heat source, with a clear switchover point.

If you have natural gas and severe winters, compare running costs before you commit. The page on heat pump vs furnace walks through that comparison and the dual fuel option.

• The house itself. Air sealing and insulation lower the heating load, which lets a heat pump cover more of the winter without backup.
• Ducts. Leaky ducts in an attic or crawlspace waste a larger share of heat when the supply air is milder.
• Outdoor unit placement. The unit should sit above expected snow depth, away from roof runoff and with clear space for airflow and defrost meltwater to drain.
• Thermostat habits. Hold a steady setpoint. Large setbacks force the system onto backup heat when it recovers.
• Electrical capacity. Electric backup strips draw a lot of current, and some panels need an upgrade.

No backup at all. Some homes in cold regions run on heat pumps alone, usually with cold-climate ductless units and a well-insulated house. That takes careful sizing, and you should ask the installer what happens on the coldest night on record.

Older standard heat pump struggling in winter. If an existing system cannot keep up, the cause may be a fault and not the climate. Have it checked before you conclude that heat pumps do not work where you live.

Power outages. A heat pump and electric backup both stop when the power does. If outages are common in winter, plan for a heat source that does not depend on the grid. The heat pump overview covers the system types.