Heat pumps work in cold weather, but their efficiency drops as outdoor temperature falls

A heat pump can heat your home even when it is freezing outside, but it will not perform the same way it does in mild weather. Most air-source heat pumps lose efficiency around 32°F and become noticeably less effective below 0°F. The system still extracts heat from cold air — there is always some heat present, even in winter — but it has to work harder and use more electricity to do it. Below a certain temperature (usually around −15°F to −25°F depending on the model), many heat pumps switch to electric resistance heating, which is far more expensive to run.

The real question is not whether a heat pump works in cold weather, but whether it makes financial sense in your climate. If you live somewhere that regularly drops below 0°F for weeks at a time, a heat pump alone may not be practical. If your winters are mild or only occasionally dip below freezing, a heat pump can handle most or all of your heating needs.

Key Takeaways

  • Heat pumps extract heat from outdoor air even in freezing temperatures, but they require more electricity as it gets colder.
  • Most air-source heat pumps lose 20 to 30 percent of their heating output between 32°F and 0°F.
  • Below −15°F to −25°F, many heat pumps automatically switch to backup electric heating, which costs significantly more to operate.
  • Cold-climate heat pumps are designed to work efficiently down to −13°F or lower, but they cost more upfront than standard models.
  • A hybrid system that pairs a heat pump with a gas furnace or backup heating is often the most cost-effective choice for regions with harsh winters.

Why heat pump efficiency drops in freezing temperatures

A heat pump moves heat from one place to another using refrigerant and a compressor. In heating mode, it pulls heat from the outdoor air and moves it inside. The colder the outdoor air, the less heat is available to extract, so the compressor has to work much harder and run longer to deliver the same amount of warmth to your home.

At 47°F, a typical air-source heat pump delivers about 100 percent of its rated heating capacity. At 32°F, that drops to roughly 70 to 80 percent. At 0°F, you are down to 40 to 60 percent. The system is still heating, but it cannot keep up with the demand on its own, especially if your home loses heat quickly or the outdoor temperature is very low.

The compressor also has to overcome frost buildup on the outdoor coil. When warm refrigerant inside the outdoor unit meets freezing air, moisture condenses and freezes on the coil. The heat pump has to periodically reverse its cycle to defrost the coil, which temporarily stops heating your home and sends warm air outside. This defrost cycle becomes more frequent as temperatures drop, further reducing the net heating output.

When heat pumps switch to backup heating

Most heat pumps have a built-in backup heating system — usually electric resistance coils — that kicks in automatically when the outdoor temperature drops below a set point. This point varies by model but typically falls between −15°F and −25°F. Some newer cold-climate heat pumps can operate efficiently down to −13°F without backup, but they are more expensive.

When the backup heating engages, your heating cost per BTU rises sharply. Electric resistance heating is about three times more expensive to run than a heat pump operating at moderate efficiency, and nine times more expensive than a heat pump at peak efficiency. If your area experiences extended periods below −20°F, you could spend significantly more on heating than you would with a gas furnace or a hybrid system.

You cannot turn off the backup heating — it is a safety feature that ensures your home stays warm even if the heat pump fails or cannot keep up. Some systems allow you to set a manual backup temperature, but most homeowners should leave this on automatic.

Cold-climate heat pumps versus standard models

Manufacturers now produce cold-climate heat pumps specifically designed to work efficiently in harsh winters. These models use variable-speed compressors, improved refrigerants, and better outdoor coil designs to maintain higher efficiency even at very low temperatures. A cold-climate heat pump might deliver 70 to 80 percent of its rated capacity at 0°F, compared to 40 to 60 percent for a standard model.

The tradeoff is cost. A cold-climate heat pump typically costs $2,000 to $5,000 more than a standard model, depending on capacity and brand. Whether that premium makes sense depends on your heating costs and how often temperatures drop below freezing in your area. If you live in a region where winter temperatures rarely fall below 20°F, a standard heat pump is usually the better choice. If you are in a place where −10°F is common, a cold-climate model may pay for itself within 5 to 10 years through lower operating costs.

Hybrid systems: heat pump plus furnace or backup

Many homeowners in cold climates choose a hybrid system that pairs a heat pump with a gas furnace or propane heater. The heat pump runs whenever outdoor temperatures are above a set point — often around 35°F to 40°F — because that is when it is most efficient. Below that temperature, the furnace takes over. This arrangement minimizes the use of expensive backup electric heating and keeps your total heating cost lower than a heat pump alone.

A hybrid system also provides redundancy: if the heat pump breaks down, your furnace can still heat the home. If the furnace fails, the heat pump can still provide some warmth. The downside is higher upfront cost and the need to maintain two separate heating systems. However, for homeowners in regions with long, cold winters, the operating cost savings often justify the extra expense.

Real-world performance in different climates

In the Pacific Northwest, where winter temperatures typically stay between 30°F and 50°F, a standard heat pump can handle 80 to 100 percent of heating needs. Backup heating rarely engages, and operating costs are low.

In the Northeast and Upper Midwest, where temperatures regularly drop to 0°F or below, a standard heat pump might cover 50 to 70 percent of heating needs, with the furnace or backup heating covering the rest. A cold-climate heat pump or hybrid system becomes more cost-effective in these regions.

In the Deep South and Southwest, where freezing temperatures are rare, a heat pump is often the sole heating system and performs very efficiently year-round.

Maintenance and winterization for cold climates

If you have a heat pump in a cold climate, keep the outdoor unit clear of snow and ice buildup. After heavy snow, brush away accumulation around the base and sides of the unit. Do not use a pressure washer, which can damage the coils.

Check your air filter monthly during heating season and replace it if it is visibly dirty. A clogged filter forces the system to work harder and reduces efficiency. Have a professional service the heat pump once a year, ideally in the fall before heating season begins. They will check refrigerant charge, inspect the coils, and verify that the defrost cycle is working correctly.

If your heat pump has a backup heating system, test it before winter to make sure it engages properly. Most systems have a manual override or test mode — check your manual or call your installer for instructions.

Frequently Asked Questions

Will a heat pump keep my home warm if the power goes out in winter?

No. A heat pump requires electricity to operate. If you lose power, the system stops working. If you have a gas furnace as backup, it will also stop unless it has a battery-powered ignition system. A generator can power both systems during an outage, but you will need to set it up beforehand.

Can I use a heat pump if I live where it gets to −30°F?

A standard heat pump will not heat efficiently at −30°F and will rely entirely on backup electric heating, which is very expensive. A cold-climate heat pump can operate at −30°F but with reduced capacity. A hybrid system pairing a heat pump with a furnace is usually the most practical choice for that climate.

Does a heat pump use more electricity in winter than in summer?

Yes. Heating requires more energy than cooling, and a heat pump works harder in winter because the temperature difference between indoors and outdoors is larger. In very cold weather, backup electric heating adds even more to your electricity use. Your winter electric bill will typically be higher than your summer bill.

What temperature should I set my thermostat to in winter to save money?

Each degree you lower the thermostat saves roughly 1 to 3 percent on heating costs. Setting it to 68°F instead of 72°F will noticeably reduce your bill. However, lowering it too far to compensate for heat pump inefficiency in cold weather often backfires: the system has to work so hard that total energy use increases. A programmable thermostat that lowers temperature when you are away or asleep is usually the best approach.

Is it worth upgrading to a cold-climate heat pump if I already have a standard model?

Only if your current system is nearing the end of its life (typically 15 to 20 years) and you are replacing it anyway. If your existing heat pump is working well, the cost of replacement usually does not pay back through energy savings alone. If you are installing a new system, the cold-climate model is worth considering if your area regularly experiences temperatures below 0°F.