How Does a Heat Pump Work in Winter? (Below 20 Degrees)

I work as a licensed HVAC contractor in Northeast Ohio and get a ton of questions on heat pumps.

The biggest question is always, “Will a heat pump heat my house when it’s really cold?” or “When does my heat pump stop making heat?” 

Heat pumps started becoming more popular in the 1970s during the oil crisis, so they’ve been around for quite a while. They have a bad name for being a little lacking in the amount of heat they can produce in colder temperatures, but that’s based on old technology.

The low temperature heat pumps of today are extremely efficient and continue to keep you comfortable down below 0°F.

Do Heat Pumps Work In Cold Weather?

Modern heat pumps in cold climates are extremely efficient and can continue to heat at very low outdoor temps making them an ideal solution to your home comfort needs. 

Not only do they heat your home, but every heat pump is also an air conditioner. So you get the comfort and efficiency in the bitterly cold winter and on those hot humid summer days.

They’re also clean green energy. They produce the least amount of carbon dioxide than standard heating sources and are great for our planet.

Heat Pump Efficiency Vs Temperature Drop

The majority of new heat pumps are efficient in extreme cold weather. However, if you have an older style heat pump, it may not be as efficient and effective as the temperature outside drops and you may want to consider a newer model.

When looking at high end models with modulating compressors, they are incredibly efficient even in cold weather.

Ductless systems don’t even use a backup heat source. They can maintain indoor comfort even when temps drop below zero. These systems are among the most efficient available today. 

Higher Upfront Cost

A big downside of modern heat pumps is the higher upfront cost than traditional HVAC systems.

As of January 1st 2023 with the Inflation Reduction Act, homeowners can claim up to a 30% federal tax credit or up to $2,000 in value when they buy an electric heat pump.

Read Also >> What Is The Ideal Furnace Temperature?

Do Heat Pumps Work Below 20 Degrees?

Absolutely. There are heat pumps on the market that can continue to heat your house even at negative temperatures such as below -15°F.

The lowest temperature the heat pump will operate will depend on the specific model. There will always be a heat pump lowest temperature where it just stops operating.

Homeowners should always verify with the manufacturer for the lowest operable temperature rating where the heat pump will quit working.

Older Heat Pumps And Low Temps

The standard ducted heat pump cannot make nearly the same amount of heat as the more efficient models and ductless systems. 

Low end systems will continue to work hard, but become less efficient as outdoor temperature plummets. Supplemental heat is a must with this type of heat pump. Back up electric heat is usually going to be used when temperatures outside drop to about 20°F. The heat pump will continue to run, but typically isn’t effective enough to heat your home by itself.

More efficient models have great technology built into them. Typically they have modulating compressors and variable speed fan motors that allow them to increase and decrease the amount of energy used to heat your home. 

Do Mini Splits Work in Cold Weather?

Ductless mini split heat pumps are the most effective type of air to air heat pump. 

They constantly move heat and use modulating inverter compressor technology to provide the most heat with the least energy. They require no supplemental back up heat source down to around -13°F. If you live in an area where temperatures drop below that, you will need another source of heat to stay comfortable.

Read Also >> Why Is Your HVAC System Leaking Water?

Should A Heat Pump Run Constantly In Winter?

There are actually two answers to this question because it depends on what type of heat pump you have.

High End

If you have a high efficient model with a modulating inverter compressor and a variable speed fan, yes. This style heat pump will run slow when it reaches temperature to help conserve energy and only ramp up when necessary. This is a normal and efficient way to operate.

Low End

If you have a lower efficiency heat pump with a standard scroll compressor and basic fan motor, no. If this system is running constant, there’s usually something wrong. Because there’s no modulation, it can’t slow down and save on energy while heating. So it’s 100% on every time it runs and will stay that way until the temperature on the thermostat is met. If it doesn’t reach your set temp, you should have it checked out by a professional.

The Negative Reputation of Heat Pumps

Heat pumps in cold weather have a long reputation for being an unreliable heat source.

The first popular heat pumps just simply weren’t very good when outdoor temps dropped below freezing. Their operating temperature range was around 30-60°F and they were primarily used in warmer climates where winter temperatures stayed fairly mild. 

Unfortunately, that reputation stuck around for a long time. Heat pump technology didn’t change a whole lot until recent years and a lot of people still think of heat pumps as they used to be instead of how they are today.

Today’s heat pumps should have no problem efficiently and effectively heating your home and keeping you comfortable, as long as they’re installed and sized properly.

RELATED: Why My Furnace Won’t Stay On?

What Is A Heat Pump & How Does It Work?

A heat pump works just like your A/C does in the summer, only in reverse. Instead of moving heat from your house outside, it moves heat from outside into your house.

Moving Heat

A heat pump isn’t creating heat, it’s moving existing heat. Moving heat is far more efficient and effective than producing it. It may sound strange that heat exists outside on a cold day, but it does and that heat can be utilized to heat your home.


The compressor pumps hot refrigerant inside through the indoor coil and the blower moves cool air from the house through it. The heat is transferred to the air and blown through your duct and out of your vents. 

Metering Device

Once out of the indoor coil, the refrigerant continues to flow to the outdoor unit where it moves through a metering device. The metering device, typically a thermostatic expansion valve or fixed orifice piston, lowers the pressure and temperature of the refrigerant. 

Heat Exchange

The refrigerant continues through the outdoor coil while the outdoor fan moves air through it. The refrigerant absorbs heat from the air and continues on into the compressor where it’s compressed and pumped back to the indoor coil. 

Read Also >> Will A Bad Thermostat Cause The Furnace Not To Work?

Frequently Asked Questions

Are There Any Downsides?

The only downside lies with the less efficient base models. They still use older technology and require supplemental heat to maintain comfort levels when outdoor temperatures get colder. This makes them cost more to operate and generally less comfortable.

Is There A Temperature Where Heat Pumps Won’t Work?

Today’s heat pumps are so good at moving heat, they continue to heat homes into negative temperatures. The vast majority of heat pumps will heat down to 0°F.

If you have a dual fuel set up, meaning you have a fossil fuel furnace for backup heat, it’s best to switch to that around 25°F. The heat pump may still be effective, but your house may lose heat faster than the heat pump can recover, and the furnace will need to take over. This depends a lot on how efficient your heat pump is, but generally they cannot run at the same time. 

What Are The Most Common Issues?

The biggest problems with heat pumps come from lack of maintenance or improper installation.  Airflow is essential for the heat pump to function properly. Regularly changing your air filter and washing your indoor and outdoor coil with help prevent pressure trips and ensure good heat exchange.

As with all systems, breakdowns happen. Parts can fail on any system, but performing regular maintenance will help prevent that and make sure your heat pump is functioning efficiently.

How Hot Can A Heat Pump Get My Home?

A heat pump can make your house as warm as you’d like. Most people keep they’re temps somewhere around 68-72, but you can set it as high as you want. Obviously the warmer you set it, the more energy you will use. So it’s best to find a happy medium between comfort and efficiency.

Final Thoughts

Heat pumps are a great source of heat and have the potential to be extremely efficient even in the coldest climates. Don’t let the bad reputation from the old days keep you from considering having one installed in your home.


Meet Your Home Inspector Secrets Author

join the 'save my home' newsletter

Get a weekly email every Tuesday with a single home maintenance tip to save, protect, and improve your house!