Do Heat Pumps Work Below 20 Degrees? (Critical Choice)

Your new heat pump worked well this summer. It did so by pulling warm air in from outside and drawing it into your home’s air vents. But as winter approaches, how can a heat pump do its job with little heat in the atmosphere for it to extract?

Do heat pumps really work when it’s below 20 degrees? Yes, they do, but not very efficiently.

Here are some of the key points that I’ll cover, plus more you’ll need to know:

• The optimum temperature range for heat pumps
• Specifics on how heat pumps work
• How heat pumps work in regions that suffer from extreme cold
• Electric backups for heat pumps
• Protecting your heat pump from extreme cold

Heat pumps work best in moderate temperatures. When temperatures drop below freezing, these pumps must have helped. If you deal with extreme cold in your region and would you’d like to learn more, please read on.

Heat pump outside of a house in snow

How Can a Heat Pump Work When the Outside Temperature is Below Freezing?

Old heat pumps struggle with frigid temperatures. Newer models with variable speeds and inverters that adjust the speed automatically handle the cold extremely well.

Having said that, heat pumps have difficulty handling ice accumulation on their coils. They must go into defrost mode in order to keep working.

In extreme cold heat pumps will need auxiliary electrical heating to keep coils clean.

How Does a Heat Pump Work At Temperatures?

A heat pump is a device that’s installed outside your home, much like an air conditioner. It draws heat into the home through the combined actions of compressors, valves, and fans.

A heat pump regulates the flow and speed to keep your home at the temperature you’ve set.

Even on cool fall days, there’s still ample heat in the atmosphere for the heat pump to tap. It does so by moving air instead of by tapping into another heating source such as gas or electricity.

Additional Benefits of Heat Pumps

Normally, heat pumps draw heat inside. But, on hot days, you can reverse this process. Simply adjust the thermostat so the heat pump extracts excess heat from inside and pumps it outside. Make sure your filter is clean before making this adjustment.

When you use a heat pump to heat your home, it’ll use less than 1 kilowatt of power to deliver 4 kilowatts worth of heat. The Department of Energy estimates heat pumps can reduce the amount of electricity your furnace uses by 50%.

That’s a good chunk of change that will stay in your pocket.

Temperature Range Outdoors for Most Effective Heat Pumping

There is enough heat energy in the air when the temperature is above 40 to heat your home. But, as the temperature falls, heat pumps must use more energy to do their job.

By the time the temperature drops below freezing, it ceases being the efficient appliance it usually is in temperate climates.

When the thermometer drops to 20 degrees, your heat pump will need auxiliary power. There isn’t enough heat in the outside air for your pump to extract.

Connect your auxiliary heating system to your heat pump system so that it will turn on as soon as the outside temperature gets too low for your pump to handle.

Try adding heat strips inside your HVAC system. They will shoulder some of the heating chores your heat pump can’t handle at low temperatures.

Use a gas furnace as a backup. At low temperatures, gas remains an efficient and reliable source of heat.

What if I Live in a Region that Suffers from Extreme Cold in the Winter?

During extremely cold winters with extended periods of sub-zero weather, heat pumps lose efficiency. They can’t produce heat fast enough to keep your house warm.

Heat pumps will require a secondary source of heat to properly heat your home. They won’t retain enough heat energy to be operational on their own.

What Kinds of Heat Pumps Work Most Efficiently in Cold Weather?

If the ground around your house retains heat even in the coldest months of winter, try a geothermal heat pump. The piping is buried deep, well below where frost can form.

If you live near water that stays open during the winter, you can use a water-sourced heat pump. The pipes are placed at the bottom of the lake or pond.

How Cold Must it Get for Heat Pumps to Completely Stop Working?

Minus 4 degrees F. is the limit for some models of air source heat pumps. Check the spec sheet for the heat pump model you’re interested in buying and compare the rating to your average winter temperature.

How Do You Configure Your Heat Pump to Work Most Efficiently in Cold Weather?

Make sure it’s connected to a backup, either electric resistance coils or a gas furnace. Set the thermostat so that the backup kicks in when it gets too cold outside for the heat pump to do its work properly.

If you live in a cold climate guaranteed to generate extended below-zero weather, consider buying a dual-fuel heat pump/gas furnace. Make sure it’s designed for extremely cold winters.

A dual-fuel system is the most energy-efficient method for managing heat pumps and cold winters.

Features of Advanced-Design Heat Pumps

These latest designs in heat pumps can help your home stay toasty warm during the coldest of cold snaps. The “desuperheater” recovers and reuses waste heat from the heat pump.

It will heat your water 2 to 3 times more efficiently than your dedicated water heater.

The scroll compressor consists of two scrolls that compress refrigerants. They last longer and provide several degrees more warm air compared to ordinary heat pumps.


  • How a Heat Pump Works – This Old House
  • What are heat pumps and why is the UK government pushing them? | Energy efficiency | The Guardian
  • Best Heat Pump Buying Guide – Consumer Reports
  • Heat pump vs. furnace: Learn the difference and find out which one is best for your home – CNET
  • Heat Pumps | Department of Energy
  • Can you use heat pumps in cold climates? | HowStuffWorks

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