Heat pumps work in cold weather, but their efficiency drops as outdoor temperature falls
A heat pump pulls heat from outside air even when it is cold, and moves that heat indoors. The colder it gets outside, the harder the heat pump has to work to extract that heat, and the less efficient it becomes. Most air-source heat pumps lose roughly 15 to 25 percent of their heating output for every 10 degrees Fahrenheit the outdoor temperature drops below 45°F. At 0°F or lower, many standard heat pumps switch to a backup heating source—usually electric resistance heat—because pulling enough warmth from freezing air costs more in electricity than generating heat directly.
Whether a heat pump makes sense for your climate depends on how often your area experiences sustained cold, what your backup heat source is, and what you pay for electricity versus natural gas or oil. A heat pump in a region that rarely drops below 20°F may run efficiently most of the year. A heat pump in Minnesota or upstate New York will rely on backup heat for weeks at a time, which changes the math.
Key Takeaways
- Heat pumps extract heat from outdoor air even in freezing conditions, but their efficiency declines sharply below 45°F and drops 15 to 25 percent per 10-degree temperature decrease.
- When outdoor temperature reaches 0°F or lower, most standard air-source heat pumps automatically switch to electric resistance backup heat because pulling enough warmth from the air becomes uneconomical.
- Ground-source (geothermal) heat pumps remain efficient in cold climates because they pull heat from soil, which stays warmer than air, but they cost significantly more to install.
- Your actual heating costs in cold weather depend on your local electricity rates, how often temperatures drop below freezing, and whether your backup heat source is electric or gas.
- Cold-climate heat pump models with larger compressors and improved refrigerant circuits perform better than standard models below 20°F, but cost more upfront.
Why efficiency drops in freezing temperatures
A heat pump works by circulating refrigerant through an outdoor coil, where it absorbs heat from the air, then through an indoor coil, where it releases that heat into your home. The temperature difference between the refrigerant and the outdoor air determines how much heat transfers. When outdoor air is 45°F, that difference is large enough that the heat transfer happens quickly and the compressor does not have to work hard. When outdoor air drops to 0°F, the temperature difference widens, and the compressor must run longer and faster to move the same amount of heat.
As the compressor works harder, it draws more electricity. At some point—usually around 0°F for a standard heat pump—the electricity cost of running the compressor exceeds the cost of using backup heat. Your system's control board detects this and switches to electric resistance heating, which is essentially a large toaster coil that generates heat directly. Resistance heat is less efficient overall, but in extreme cold it is cheaper than forcing a heat pump to work at its limit.
How backup heating affects your winter costs
Most heat pump systems include a backup heat source, either electric resistance coils built into the indoor unit or a connection to an existing furnace. When the outdoor temperature drops below your system's balance point—typically 25°F to 35°F for a standard heat pump—the backup automatically engages. From that point until temperatures rise again, you are paying for two forms of heating: the heat pump (which still runs but at reduced efficiency) and the backup.
If your backup is electric resistance, your heating costs will rise noticeably during cold snaps because resistance heat is expensive to run. If your backup is a gas furnace, your costs depend on local gas prices relative to electricity. In regions where electricity is cheap and gas is expensive, a heat pump with electric backup may still cost less than a furnace alone. In regions where gas is cheap, a heat pump may increase your winter bills.
The balance point—the outdoor temperature at which your backup kicks in—varies by model and by how you set your thermostat. A higher indoor setpoint (72°F instead of 68°F) lowers the balance point, meaning backup heat engages sooner and runs more often.
Cold-climate heat pump models perform better than standard models
Manufacturers now offer heat pumps specifically designed for cold climates. These models use larger compressors, improved refrigerant blends, and variable-speed motors that allow the compressor to ramp up gradually instead of cycling on and off. Cold-climate models maintain reasonable efficiency down to 0°F or even lower, and some can heat without backup down to -13°F.
The trade-off is cost. A cold-climate heat pump typically costs $1,000 to $3,000 more than a standard model. Whether that premium pays for itself depends on how often your area experiences sustained cold and how much you save on heating bills over the system's lifetime. In a climate where temperatures regularly drop below 0°F for weeks, a cold-climate model may reduce backup heat use enough to justify the extra expense. In a climate where freezing temperatures are rare and brief, a standard model with electric backup may be cheaper overall.
Ground-source heat pumps maintain efficiency in cold climates
A ground-source heat pump (also called geothermal) pulls heat from soil or groundwater instead of outdoor air. Soil temperature stays relatively constant year-round—usually 45°F to 55°F depending on your region and depth—so a ground-source system does not lose efficiency as outdoor air temperature drops. A ground-source heat pump can heat efficiently even in Minnesota winters without relying on backup heat.
The drawback is installation cost. A ground-source system requires drilling wells or burying loops of pipe underground, which costs $15,000 to $30,000 or more depending on soil conditions and property size. That high upfront cost means ground-source systems make sense only if you plan to stay in the home for 15 to 20 years and have the space and budget for installation. For most homeowners in cold climates, a standard or cold-climate air-source heat pump with backup heat is the practical choice.
Comparing heat pump costs to furnaces in cold regions
In a cold climate, a heat pump will not outperform a furnace on heating alone. A furnace generates heat directly and does not lose efficiency as temperature drops. However, a heat pump offers year-round value because it also cools in summer, while a furnace does not. If you currently use a furnace and air conditioner separately, a heat pump replaces both with one system, which can lower your total annual energy cost even if winter heating costs are higher than a furnace alone.
The comparison also depends on fuel prices in your area. If natural gas is significantly cheaper than electricity, a gas furnace will heat more cheaply than a heat pump in winter. If electricity and gas prices are close, or if electricity is cheaper, a heat pump may cost less overall despite backup heat use. Your local utility can provide historical rates for both fuels, which lets you estimate winter costs for each option.
Steps to improve heat pump efficiency in cold weather
If you already have a heat pump or are considering one for a cold climate, several practices reduce backup heat use and lower winter bills. Keep your thermostat setpoint as low as you can tolerate—each degree lower reduces heating demand. may support your home is well-insulated and air-sealed, because heat loss directly increases the load on your heat pump. Have your heat pump serviced annually before winter to may support the outdoor coil is clean and the refrigerant charge is correct; a dirty coil or low charge forces the compressor to work harder.
If your system has a programmable or smart thermostat, avoid setting it to switch to backup heat too early. Some thermostats allow you to adjust the balance point; lowering it slightly (if your comfort allows) keeps the heat pump running longer before backup engages. However, do not lower it so far that your home becomes uncomfortable—the goal is efficiency, not discomfort.
Frequently Asked Questions
Will a heat pump work at all when it is 10 degrees outside?
Yes. A heat pump will extract heat from 10-degree air and move it indoors. However, it will be running at very low efficiency and will likely have switched to backup heat already. Your system will keep your home warm, but you will be paying more for that warmth than you would in milder weather.
Can I use a heat pump as my only heating source in a cold climate?
Technically yes, but it is not practical for most cold climates. Without backup heat, your system would have to run continuously during cold snaps, consuming enormous amounts of electricity. A backup heat source (electric resistance or gas furnace) is standard because it is cheaper to use when outdoor temperatures drop very low.
How do I know if my heat pump is switching to backup heat?
Most thermostats display which heating source is active, or you can check your system's control panel. You can also monitor your electric meter or utility bill; a sharp increase in electricity use during cold weather often signals that backup heat is running frequently. If you have a gas furnace as backup, you will see increased gas usage instead.
Is a heat pump worth it if I live somewhere that gets very cold?
It depends on your current heating and cooling setup and local fuel prices. If you use both a furnace and an air conditioner, a heat pump may lower your total annual energy cost even if winter heating costs more than a furnace alone. If you use only a furnace and rarely cool, a heat pump may not save money. Compare your current annual heating and cooling costs to estimates for a heat pump system in your climate.
What is the difference between a standard heat pump and a cold-climate heat pump?
A cold-climate heat pump uses a larger compressor and improved refrigerant to maintain efficiency down to 0°F or lower, reducing reliance on backup heat. A standard heat pump loses efficiency below 45°F and typically switches to backup around 25°F to 35°F. Cold-climate models cost more upfront but may reduce backup heat use significantly in regions with sustained freezing temperatures.