A heat pump heats your home in winter by pulling heat from outdoor air — even when it is freezing outside. That sounds impossible to many homeowners who remember older heat pumps blowing lukewarm air. Modern cold-climate heat pumps have changed what is possible.
Key Takeaways
- Heat pumps move heat using a refrigerant cycle rather than burning fuel or using resistance heating, which makes them very efficient.
- Efficiency falls as outdoor temperatures drop, but cold-climate models are designed to keep producing useful heat in sub-freezing weather.
- HSPF2 measures heating efficiency and SEER2 measures cooling efficiency; higher is better.
- Proper sizing and installation matter as much as the equipment.
How a heat pump works
A heat pump uses a refrigerant that absorbs and releases heat as it changes between liquid and gas.
In heating mode:
- The outdoor coil absorbs heat from outdoor air, even cold air.
- A compressor raises the refrigerant’s temperature.
- The indoor coil releases heat into your home.
- The refrigerant returns outdoors to repeat the cycle.
In cooling mode, the process reverses, like an air conditioner.
Why it is efficient
Because a heat pump moves heat rather than creating it, it can deliver more heat energy than the electrical energy it uses. This ratio is the coefficient of performance (COP). A COP of 3 means three units of heat for one unit of electricity. Electric resistance heaters have a COP of 1.
Cold weather performance
As outdoor temperatures fall, there is less heat to extract and efficiency drops. Older heat pumps often relied heavily on backup resistance heat in cold weather.
Cold-climate heat pumps use variable-speed (inverter) compressors and improved refrigerant systems to maintain capacity at lower temperatures. Many are designed to provide substantial heat well below freezing. Manufacturer specifications and independent listings, such as cold-climate product lists, show capacity at specific temperatures.
Efficiency ratings
- SEER2: seasonal cooling efficiency.
- HSPF2: seasonal heating efficiency.
- COP at specific temperatures: useful for cold climates.
Ratings were updated in 2023 to new test procedures, hence the “2” in the names.
Backup heat
Some homes keep a furnace or electric resistance strips as backup for extreme cold. Dual-fuel systems switch to a furnace below a set temperature. The best approach depends on climate, fuel prices and existing equipment.
Ducted vs ductless
- Ducted heat pumps replace or work with central systems.
- Ductless mini-splits heat and cool individual rooms or zones.
Questions for installers
- Did you perform a load calculation (Manual J)?
- What capacity does the unit provide at our design temperature?
- How will defrost cycles be handled?
- What backup heat do you recommend?
- What are the warranty terms?
Frequently Asked Questions
Do heat pumps work below 0°F? Some cold-climate models still provide heat at very low temperatures, with reduced capacity.
Are heat pumps noisy? Modern units are relatively quiet; placement matters.
Will my electric bill go up? Electricity use rises if replacing gas, but overall heating costs depend on rates and efficiency.
Do heat pumps need maintenance? Yes — filters, coil cleaning and periodic checks.
The bottom line
Modern heat pumps can heat homes efficiently in many climates, including cold ones, when properly sized and installed. Look at cold-weather capacity, not just headline efficiency.
