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How Does A Heat Pump Work In Winter? All You Need to Know

A heat pump is designed to use a coolant to absorb heat from the outside air and radiate this heat inside your home to heat the air inside. While it is understandable how this works when the air is warm outside, how does it work when the air outside is freezing? How does a heat pump work in low winter temperatures?

Heat pumps work in winter by reversing the direction of flow of the refrigerant in its internal loop. This allows the unit to absorb heat from the outside air, even in low temperatures, and transfer this heat inside your home, where it warms the air. Heat pumps do not work well below 20° Fahrenheit.

A heat pump can work bi-directionally, meaning it can deliver heat to your home or extract heat from your home. A heat pump uses ambient outside temperature for the heat transfer, so how does a heat pump warm up the air in your home if the outside air is cold? Heat pumps have some limitations regarding the outside temperatures in which they can work efficiently.

How a Heat Pump Works in Winter

Most people can understand how a heat pump can work efficiently in the summertime, but the process of how it works in the wintertime is a mystery to some folks.

A heat pump works with a refrigerant in piping that is piped through your home. The refrigerant is a substance that is able to absorb heat very efficiently. In the summertime, as the refrigerant is pumped through your home, it absorbs heat from the air inside your home.

The now warmed refrigerant is pumped outside your home to the heat pump unit, where the absorbed heat is radiated out into the outside air. Sometimes fans are used to cool the piping, which helps to extract the heat from the coolant.

This heat transfer is logical and makes sense to most people. So how does a heat pump work to warm your home in winter? The flow in a heat pump is a looped system, and the flow is reversed in the wintertime so that the heat transfer is reversed as well.

In the wintertime, the refrigerant works by absorbing warmth from the outside air. Outside air, even in the winter, has warmth that can be absorbed into the refrigerant. This may seem illogical, but a heat pump can absorb heat from the outside air in temperatures as low as 20° Fahrenheit or -6.6° Celsius. 

It may seem incredible, but these units can extract heat from the air in freezing temperatures. However, heat pumps do have their limitations in extremely cold conditions.

What Are Heat Pump Limitations In Cold Weather?

Heat pumps are generally installed in locations where the winters are considered to be mild. Even though a heat pump can absorb heat from the outside air in temperatures as low as 20° Fahrenheit, it is not efficient at temperatures this low or lower for sustained periods.

When the winter temperatures drop to consistently below 25° Fahrenheit, a heat pump is no longer an efficient method of transferring heat. In locations where the winter temperatures are consistently below this level, hybrid heat pump systems are often used to improve efficiency in the coldest parts of the season.

In hybrid heat pumps, additional means may be incorporated to heat the refrigerant, such as an electrical heating element

A heat pump works most efficiently when the outside temperature is 40° Fahrenheit or above. It will work for short durations where the temperature drops below this point but will struggle to maintain efficiency for extended cold periods.

In these colder temperatures, you may find that your heat pump is running continuously to try and keep the air temperature in your home at the required setting. This will cause the unit to work harder, using more electricity and losing effectiveness as an efficient warming solution for your home.

How To Improve Heat Pump Performance For Winter

If your winter temperatures are mild, a heat pump is a good choice for warming your home, and in the summertime, it can reverse its role and cool your home down. This means it can serve both functions without the need for a second system, much the same as an air conditioning unit.

Heat pumps are popular for several reasons.

  • Heat pumps are energy efficient. A heat pump can be more cost-effective to run than other heating and cooling systems.
  • Heat pumps are safe. The heating and cooling mechanisms of the unit use less hazardous substances than other systems. The unit does not need a heat source since it does not generate heat but rather transfers heat from one location to another.
  • Heat pumps are durable. Heat pumps have a much longer lifespan than many other types of heating and cooling systems. Some units have been known to function well for 50 years or more.

Knowing that heat pumps are designed for areas with milder winters, what can you do to improve the efficiency of your unit in the colder months?

  • Keep the filter clean. Dust build-up in drier months can clog the heat pump filter, which reduces the heating efficiency of the unit. 
  • Keep the garden area around your heat pump clean. Heat pumps need to breathe and need clear air vents around the unit. Remove the build-up of leaves or other debris around the casing of the heat pump.
  • Do not cover your heat pump. Some people think they are protecting the heat pump unit by placing a cover over it in the winter. As we have already said, a heat pump needs to breathe to work efficiently. A cover is counter-productive and can cause damage to your unit.
  • Don’t crank the temperature too high. Trying to make your home too warm is going to make your heat pump work hard and consume more electricity. Keep your internal temperature at a temperature of between 68° Fahrenheit or 20° Celsius and 75° Fahrenheit or 24° Celsius. If you find this a little chilly in the winter, put a sweater on.
  • Service your heat pump regularly. Most manufacturers recommend that your heat pump be serviced by a certified technician at least once a year. Keeping up a regular service and maintenance schedule on your heat pump will ensure it is running at optimal efficiency, reducing your energy bill.

If your heat pump is laboring to try and warm your home up, it will be running almost continuously, which increases the amount of energy the unit will consume. This can accumulate over the cold months and result in a high utility bill.


Heat pumps can be an effective, efficient heating solution for your home, except in regions that experience extremely cold temperatures below 20° Fahrenheit for extended durations. In colder winter regions, hybrid heat pump systems are often used to improve the efficiency of the unit.

In the winter setting on your heat pump, the flow of the refrigerant is reversed to absorb ambient heat from the outside air, even in cold conditions, and transfer this heat into your home, where it will raise the internal air temperature.

In regions with mild winter temperatures, heat pumps are a good choice and also a more environmentally friendly choice to heat your home.


  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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