Many Minnesota homeowners ask the same question: can a heat pump keep a house warm when it is 15 below outside? The short answer is yes, with the right equipment and a plan for the coldest days. Older heat pumps lost most of their heating output in deep cold. Today's cold-climate models are built to keep heating at much lower temperatures. This guide explains how they work, what the cold-climate rating means, and why most Minnesota installations still include a backup heat source.
How a heat pump heats your home in cold air
A heat pump does not burn fuel. It moves heat. In heating mode, refrigerant in the outdoor coil absorbs heat from the outside air and evaporates. The compressor pressurizes that refrigerant, and the indoor coil releases the heat into your home. Outdoor air at 0°F still contains heat that the system can collect.
The catch is that the colder the air, the harder the system works to collect that heat. Two things drop as the temperature falls:
- Capacity: how much heat the unit can deliver per hour.
- Efficiency: how much heat you get for each unit of electricity used, measured as the coefficient of performance (COP). A COP of 2 means the heat pump delivers twice as much heat as the electricity it uses. Electric resistance heat, such as baseboard heaters, has a COP of 1.
At the same time, your home loses heat faster as it gets colder outside. On the coldest nights, the heat pump's output can fall below what the house needs. That is the gap a backup heat source covers.
What makes a heat pump "cold climate"
Cold-climate heat pumps use variable-speed (inverter-driven) compressors. The compressor speeds up when it is cold outside to hold more of its heating output. The U.S. Department of Energy's air-source heat pump guide advises homeowners in colder climates to look for the highest heating efficiency rating (HSPF) that is practical for their home.
ENERGY STAR has a specific cold-climate designation. According to ENERGY STAR's air-source heat pump page, certification requires third-party verified low-temperature performance, with testing down to 5°F. To qualify as cold climate, ENERGY STAR's criteria require a unit to:
- Reach a COP of at least 1.75 at 5°F.
- Deliver at least 70% of its rated 47°F heating capacity at 5°F.
These numbers matter in Minnesota because they show how a unit performs in the temperatures you see for weeks every winter, not only in mild weather.
What happens on sub-zero days
Cold-climate heat pumps keep running below 5°F. ENERGY STAR notes that pairing one with a backup heat source is the most efficient approach when temperatures drop even lower. In Minnesota, backup heat usually comes in one of these forms:
- Gas or propane furnace (dual fuel): the heat pump handles heating until a set outdoor temperature, then the furnace takes over.
- Electric resistance heat strips: installed in the indoor air handler. They turn on when the heat pump cannot keep up.
- Existing boiler or baseboard heat: common with ductless systems added to part of a home.
A heat pump without any backup can work in a very well insulated home, but it depends on the equipment, the house and how cold your location gets. A contractor should calculate your home's heating load and compare it with the unit's published capacity at low temperatures before you rely on it alone.
Ducted vs. ductless options
If your home has ductwork from a furnace and central air conditioner, a ducted heat pump can replace the air conditioner and use the same ducts. It cools in summer and heats through much of the heating season. If you have a boiler, baseboard heat or rooms without ducts, a ductless mini-split heat pump can heat and cool individual rooms or zones. Both types are available in cold-climate models.
What you can check before you talk to a contractor
You can gather useful information on your own:
- Note your current heating system. Write down the furnace or boiler's age and fuel type, and whether you have central air.
- Look at your insulation and drafts. Check attic insulation depth and look for drafty windows and doors. A tighter home needs less heat, so a heat pump covers more of the winter.
- Find your electrical panel's amperage. It is usually printed on the main breaker. A heat pump with electric backup strips may need more electrical capacity than you have.
- Pick a spot for the outdoor unit. It needs to sit above expected snow depth, away from roof drip lines, with clear airflow around it.
- Gather a year of energy bills. They help a contractor estimate how your costs would change.
Do not open electrical panels or handle refrigerant lines yourself. Refrigerant work requires EPA-certified technicians.
When to call a professional
Talk to a heating contractor when your furnace or air conditioner is nearing replacement, when you want to cut your use of gas, propane or electric resistance heat, or when you want heating and cooling in rooms without ducts. Ask for a heating load calculation, the unit's capacity at 5°F, and a clear plan for backup heat. Krinkie's can review your home and explain your heat pump installation options for a Minnesota winter.
Common questions
At what temperature does a heat pump stop working?
It depends on the model. Cold-climate heat pumps are tested down to 5°F for ENERGY STAR and keep running below that, but their output drops, so Minnesota homes usually keep a backup heat source for the coldest days.
What does ENERGY STAR cold climate mean?
It means the heat pump meets ENERGY STAR's low-temperature criteria, including a COP of at least 1.75 at 5°F and at least 70% of its rated 47°F heating capacity at 5°F.
Do I need to remove my furnace to get a heat pump?
No. Many Minnesota homes keep the furnace as backup heat in a dual-fuel setup, with the heat pump handling milder weather and the furnace taking over in deep cold.