What does a heat pump actually do on a -20°F night in Minnesota?
On a -20°F Minnesota night, a heat pump runs at reduced output or locks out, and the furnace or electric backup carries most of the load. That handoff is normal. If the house still falls behind with backup running, call 612-429-3465.
Key points
- At -20°F most Minnesota heat pump systems are running mostly on backup heat, and that is how they are designed.
- Many cold-climate units are rated to heat down to -13°F; a few newer models list -20°F or -22°F.
- Full rated capacity at a cold temperature is not full efficiency; power use climbs as it gets colder.
- A quiet outdoor unit on a cold night is usually a switchover, a lockout, a defrost or utility control, not a failure.
- Use emergency heat only when the outdoor unit has failed or is iced solid.
Backup heat running at -20°F is not a sign that something broke, and it is not a reason to regret the heat pump. A heat pump earns its keep on the hundreds of hours between the first frost and the deep cold, not on the coldest night.
What does a heat pump do hour by hour on a -20°F night?
A typical dual-fuel or electric-backup system behaves like this as an arctic front settles in. The exact temperatures depend on your equipment and how it was set up.
- Evening, around 10°F. The heat pump runs at high speed and may run for hours without stopping. For a variable-speed unit, that is normal. The air at the registers feels warm, not hot.
- Late evening, near zero. The heat pump's output is falling while the house's heat loss is climbing. On a dual-fuel system the thermostat reaches the switchover point and fires the furnace, and the outdoor unit goes quiet. On an electric-backup system the heat strips stage on and the thermostat shows "aux heat."
- Overnight, -15°F to -20°F. Many cold-climate outdoor units reach their rated limit in this range and lock out the compressor. The outdoor fan stops, nothing is wrong, and the backup carries the house.
- Morning, warming back up. Once the outdoor temperature climbs past the lockout or switchover point, the heat pump takes over again on its own.
Defrost cycles tend to thin out in the deepest cold, because very cold air holds little moisture. The busiest defrost days are the damp ones in the 20s and 30s, which our post on the defrost cycle walks through.
How cold are heat pumps rated to heat?
The table below lists each manufacturer's own published figures. "100% capacity" means the unit can still deliver its full rated heating output at that temperature. It says nothing about efficiency, which drops as the compressor works harder.
| Equipment | Maker's stated low-temperature heating |
|---|---|
| Mitsubishi Hyper-Heating INVERTER (H2i) | Up to 100% capacity at 5°F; heats down to -13°F |
| Mitsubishi H2i plus | 100% capacity down to -5°F; heats down to -13°F |
| Mitsubishi H2i sumo | 100% capacity at -10°F; heats down to -22°F |
| Daikin FIT (DH7VS) | Heating operating range down to -10°F |
| Daikin FIT Aurora (DH9VS) | Heating operating range down to -20°F; ENERGY STAR cold-climate certified |
Sources are Mitsubishi Electric's product glossary and Daikin's current spec sheets. Our Mitsubishi and Daikin pages cover the brands in general. For any other model, look it up on the NEEP cold-climate heat pump list, which shows heating capacity and efficiency at 5°F. Compare the 5°F capacity with your house's heat loss, not the lowest temperature on the brochure.
Why keep backup heat with a heat pump in Minnesota?
There are two reasons, one about sizing and one about risk.
Sizing. A heat pump big enough to heat a typical Minnesota house by itself at -20°F would be far larger than the house needs on a 30°F day or in July. An oversized heat pump runs in short bursts in mild weather and leaves the house clammy in summer. Variable-speed models throttle down well, but there are limits. It usually makes more sense to size for most of the winter and let the backup cover the deepest cold.
Risk. If a heat pump is the only heat and it needs a part on a -20°F night, you are waiting on that part with the pipes at stake. A furnace or backup strips behind it keep the house warm regardless. The trade-offs between those two backups are in our dual-fuel guide.
Why does a heat pump's outdoor unit go quiet in winter?
A silent outdoor unit worries people more than anything else a heat pump does. In Minnesota there are three common reasons besides the low-temperature lockout, and none of them is a breakdown.
- The switchover point. On a dual-fuel system, the installer sets an outdoor temperature below which the furnace takes over. Where it sits depends on the heat pump's cold-weather output, how much heat the house loses, and what you pay for gas and electricity, so two neighbors with the same equipment can switch at different temperatures.
- Utility control. Dakota Electric and Connexus Energy both run dual-fuel programs. On those, the utility can switch the heat pump off during peak demand, and the furnace heats the house until the control period ends. If your outdoor unit stops on a cold weekday evening while the furnace runs fine, check your enrollment before you call.
- Defrost. The outdoor fan stops, the unit hisses and steams for a few minutes, then starts again.
How does a winter power outage affect a heat pump?
A gas or propane furnace needs only enough electricity to run its blower, inducer motor and controls. A heat pump, and especially electric backup strips, draws far more. If you plan to run a generator through a winter outage, that difference decides what the generator can keep going, so ask your electrician which equipment it will power. It is one more reason rural homes on propane often keep the furnace as the backup.
What's normal on a cold night, and what isn't?
| What you notice | What it usually means | What you can do | Who handles it |
|---|---|---|---|
| Outdoor unit stopped, "aux heat" showing or the furnace running, house holding temperature | Switchover, low-temperature lockout or utility control | Nothing | No one |
| Outdoor unit steaming, fan stopped for a few minutes | Defrost cycle | Wait; it restarts on its own | No one |
| Ice building on the coil or base and not clearing between defrosts | Drifted snow, a dripping roof edge, poor drainage under the unit, or a defrost fault | Clear snow by hand and stop the drip; don't chip ice | A technician if it stays iced |
| House losing ground while the backup runs | A failed heat strip, a furnace problem, an undersized backup or a clogged filter | Replace the filter and open closed registers | A technician |
| Backup never comes on as it gets colder | Thermostat settings, a tripped breaker for the heat strips, or a furnace that won't light | Check the thermostat mode; reset a tripped breaker once | A technician if it trips again |
| Error code on the thermostat or outdoor unit | A sensor, pressure or communication fault | Write the code down | A technician |
How should you prepare a heat pump for a cold snap?
- Clear the outdoor unit. Shovel snow away from the sides and brush drifts off the top. Air has to move through the coil.
- Look for dripping water. A gutter or roof edge dripping on the unit builds ice fast in a thaw-freeze cycle.
- Leave the ice alone. Don't chip at the coil or pour hot water on it. The fins bend easily and the tubing can puncture.
- Know your thermostat's heat modes. "Aux heat" means the backup is helping automatically. "Emergency heat" shuts the heat pump off and runs only the backup. Use it only if the outdoor unit has failed or is iced solid, and call us.
- Change the filter. A clogged filter hurts a heat pump in heating mode as much as in summer.
What does a heat pump repair visit cost?
A repair visit starts with a $79 trip charge, waived when you approve the repair, and you get a written, flat-rate price before any work begins.
If you're shopping for a system that handles a Minnesota January, a ducted heat pump runs $7,500–$14,500 installed with us and a ductless system $4,200–$12,500. A cold-climate model sized to carry more of the winter sits higher in that range than one that hands off early to a healthy gas furnace. Our heat pump installation cost guide breaks down what moves the price, and our page on heat pumps in Minneapolis covers how they fit the city's older houses.
On incentives: Xcel Energy lists cold-climate heat pump rebates, so ask whether the one you want needs a registered contractor before you count on it. CenterPoint Energy's ducted heat pump rebate applies only when the heat pump is paired with a gas furnace as a dual-fuel system. The federal 25C credit does not apply to equipment placed in service after December 31, 2025, and Minnesota's HEAR and HOMES rebates had not launched as of mid-2026. Amounts change every year, so check the utility's page.
When should you call about a heat pump in deep cold?
Call if the house keeps falling behind even though the backup is running, if the backup never comes on as the temperature drops, if the outdoor unit is encased in ice that defrost doesn't clear, or if the thermostat or outdoor unit shows an error code. The same goes for a furnace that won't fire when the heat pump hands off; see furnace repair, and our no-heat checklist covers what to check while you wait. No-heat calls get priority. We answer at 612-429-3465, 7am to 9pm every day. For the bigger picture on choosing a system, read do heat pumps work in Minnesota winters or see our heat pump service page.
Common questions about heat pumps
Will my heat pump be damaged running at -20°F?
No. Units built for cold climates protect themselves. When the outdoor temperature drops below the rated limit, the control locks out the compressor and lets the backup heat run. What damages outdoor units in deep cold is ice: snow drifts, dripping gutters, or defrost water refreezing under a unit that sits on the ground.
Can a generator run my heat pump in a winter outage?
Ask an electrician which equipment your generator can power before you need it. Electric backup strips draw far more than a furnace's blower and controls, so a house with a gas or propane furnace behind the heat pump is easier to keep warm through an outage.
Which heat pumps are rated below -13°F?
A handful of newer models, listed in the table above. Even those lose output in deep cold, so a Minnesota house needs a furnace or electric backup behind the heat pump either way. For other models, the NEEP list shows capacity at 5°F.
How do I know my heat pump has locked out in deep cold?
The outdoor fan and compressor sit still while warm air still comes from the vents, because the furnace or electric strips took over below the lockout temperature. That is normal. If no heat comes from the vents at all, or the thermostat shows an error, check the breakers and thermostat, then call 612-429-3465.
Sources
- NEEP Cold Climate Air Source Heat Pump List ashp.neep.org
- ENERGY STAR energystar.gov