Can a Heat Pump Work in Cold and Hot Temperatures?

  • August 12, 2022
  • By MR COOL

If you’re looking for cost-effective, energy-efficient and low-maintenance ways to heat and cool your home, then a heat pump may be the solution. Though heat pumps are becoming increasingly popular in new residential homes and as furnace or air conditioning replacements in existing homes, there are still misconceptions about how heat pumps work and what types of climates they’re suitable for. 

This guide to heat pumps explains how these devices provide both cooling and heating. We also cover what you need to know about operating a heat pump in either extremely hot or freezing cold temperatures.

How Does a Heat Pump Work?

A heat pump is a device that provides heating and cooling to an indoor residential space using the principle of heat transfer. It’s an energy-efficient alternative to traditional heating and cooling options like furnaces and air conditioners. 

These all-in-one solutions come with both an indoor and an outdoor unit, each with its unique role depending on the season. The indoor unit gets mounted in a central location inside your home, typically toward the ceiling. The outdoor unit gets installed in an unobstructed location outside your home, typically in the side or backyard.

Below is how a heat pump works in heating mode:

  1. The outdoor unit extracts heat from the cold, outdoor air, compressing it to maximize its heat energy.
  2. The heat energy is transferred to the indoor unit via a refrigerant line.
  3. The indoor unit further heats up the air by condensing the air as a fan blows it across a coil.
  4. The indoor unit circulates the warm air throughout the home via ducts and vents.

And here is how a heat pump works in cooling mode:

  1. The indoor unit pulls warm air from inside the home into the unit using a fan.
  2. The indoor unit fan blows the warm air across a coil containing refrigerant that absorbs the heat, cooling it down.
  3. The cool air gets circulated throughout the home.
  4. The refrigerant that absorbed the heat energy evaporates into a gas, which gets compressed and sent outside via the outdoor unit.

Both the heating and cooling modes repeat on a continuous cycle to maintain the desired ambient temperature.

Can a Heat Pump Work in Cold Weather?

Heat pumps are designed to work year-round, meaning they’re both a heating and cooling solution. Heat pumps are necessary in cold weather, as they keep a home warm. But, like all powered devices, heat pumps will reach a certain maximum efficiency rating, which dwindles in extreme conditions. When the outdoor temperature is extremely cold, a heat pump typically becomes less efficient at heating a home. That’s because it has to work harder to produce heat, meaning it uses more energy.

To heat air in the wintertime, the heat pump needs to be able to cool down the refrigerant so it’s cooler than the outside air. How much colder the refrigerant gets than the outside air is what determines its efficiency. Therefore, when temperatures are extremely low, the refrigerant can’t get any colder and the unit loses its ability to extract heat from the air.

Heat pumps have efficiency ratings measured in British thermal units per hour (Btu/hr), which is how much heat energy the unit can provide to a space. Thermal output fluctuates depending on the outdoor temperature. So, a unit that delivers 50,000 Btu/hr at 50 degrees Fahrenheit might drop to a 40,000-Btu/hr output at 35 degrees Fahrenheit.

Can Heat Pumps Work Below Freezing?

Manufacturers provide a heat pump minimum temperature rating for a certain temperature range, traditionally with a minimum operating efficiency at around 30-40 degrees Fahrenheit. However, many of today’s heat pump units are designed with extremely efficient heating capabilities, meaning some cold-climate heat pumps can continue to pull heat in temperatures as low as 5 degrees Fahrenheit. The 12k, 18k, and 24k BTU 4th Gen DIY ductless mini-splits can heat in temperature as low as -13 degrees Fahrenheit.

In climates where temperatures drop below 20 or 30 degrees Fahrenheit frequently, home builders and homeowners typically install a backup heat source to compensate for the time when a heat pump isn’t sufficient. These emergency sources of heat are usually electric baseboard heaters or gas-powered heaters. 

With cold-climate heat pumps, homeowners can drastically cut their conventional heating costs in the winter by taking advantage of these high-efficiency heating units.

Do Heat Pumps Work in Hot Weather?

Many people think of heat pumps as simply a household heating solution. But heat pumps work to cool homes, too, and are capable of working in hot weather, just like an air conditioner.

According to the Department of Energy, heat pumps work as well at conditioning an equivalent-sized space as an air conditioner but they dehumidify better and work more efficiently. For this reason, many households are switching from air conditioning units to heat pumps to replace their cooling needs. Since heat pumps also provide heating, it means that homeowners now have a single unit to manage rather than an air conditioner and a furnace.

Just as heat pumps have to work harder in the winter to pull heat from the extremely cold air, these units also work overtime in the summer to cool down hot air. If outdoor temperatures reach extreme highs of 95-100 degrees Fahrenheit, then the heat pump’s efficiency will be affected, and it will be less able to provide comfortable cooling abilities. 

New, high-efficiency heat pump units are becoming increasingly more capable of cooling down residential spaces when temperatures reach extreme highs. Heat pumps are also effective in humid climates and can keep pace with heat waves or spikes in temperature. 

At What Temperature Do Heat Pumps Lose Their Efficiency?

Heat pumps are designed and engineered to work efficiently, making them a cost-effective and energy-efficiency alternative to many conventional cooling and heating sources. However, their efficiency wanes when temperatures veer to the extremes.

Below is a comparison between how heat pumps lose their efficiency in heating vs. cooling scenarios. 

Heat Pump Heating Efficiency

What’s the lowest temperature a heat pump will work? Generally speaking, most heat pumps operate at their top efficiency levels while outdoor temperatures are 30-40 degrees Fahrenheit or higher. Any lower than that and the unit will consume more energy trying to heat your home, increasing your energy bills.

Thankfully, there are steps that homeowners can take to improve heat pump heating efficiency, including:

  • Install wind baffles: In extremely cold climates, it’s recommended to install wind baffles on the outdoor unit. Wind baffles prevent air from blowing into and through the outdoor unit to preserve efficient performance during low temperatures. Also acting as air diverters, wind baffles direct air upward and away from the outdoor unit, protecting nearby structures and obstructions from expelled air. 
  • Perform a winter cleaning: All equipment performs best when it’s been well-maintained and is in good working condition. During the winter, your heat pump will undergo heavy use, so make sure the filter is clean and replace it if necessary. You can also call a professional to have your heat pump inspected to ensure it’s functioning properly. 
  • Winterize your outdoor unit: During the winter, the outdoor unit coil can start to accumulate ice. The outdoor unit is equipped with a defrost setting that will automatically use hot gas to melt ice from the coil. However, if too much snow or debris accumulates in front of the outdoor unit, it’s important to clear it away. If you live in a rainy or snowy climate, you’ll also need to install a gutter or rainwater diverter to prevent roof water runoff from damaging the outdoor unit.

Heat Pump Cooling Efficiency

Heat pumps are becoming an increasingly preferred option to air conditioning units in warm-weather climates. That’s because they operate extremely efficiently, even at high temperatures. While heat pumps can work in hot weather, the hotter it gets, the less efficient they may become. When it’s 90 degrees Fahrenheit outside or more, it may take a heat pump several hours to bring the indoor ambient temperature down to a comfortable 70 degrees.

The ideal heat pump effective operating temperature for cooling is 20 degrees lower than the outdoor temperature. To maximize heat pump cooling efficiency in the summer, you should never set your heat pump temperature higher than 80 degrees Fahrenheit, which is sufficient on the hottest days of 100-degree weather.

How to Heat Your Home When Temperatures Are Low

Be prepared to properly manage your heat pump during winter cold snaps. Taking certain precautions and following some best practices can help improve heat pump efficiency when it’s cold out.

Below are some tips on how to heat your home with a heat pump during the winter:

  • Use the heat pump in moderation: Keep your heat pump’s temperature set to a moderate setting. Don’t set it higher during the winter than is necessary — between 66 and 70 degrees Fahrenheit — and avoid running it continuously. Set the heat pump to heat mode rather than auto to reduce the amount of energy that’s needed during auto mode, which automatically switches between heating and cooling.
  • Never cover a heat pump during the winter: Some people mistakenly believe they need to cover or protect their outdoor unit when temperatures drop. Heat pump outdoor units need an exhaust clearance of 2 feet. Your outdoor unit does not need to be covered during the winter to protect it, as it’s designed to withstand cold, outdoor conditions.
  • Use the heat pump according to instructions: Follow the manufacturer’s instructions, including seasonal directions for how to use it during the winter. Checking out the manual helps you better manage your heat pump and maximize its efficiency, and it will also protect your warranty if the unit happens to malfunction.
  • Avoid switching to emergency heat: Heat pumps with emergency heat settings will automatically switch to the supplemental heating source as necessary. Avoid manually switching to emergency heat unless you are sure your heat pump isn’t working. Switching your heat pump to emergency heat manually may cause your heat to be supplied entirely by the emergency source, leading to a major increase in energy consumption and costs.

How to Cool Your Home When Temperatures Are High

Using a heat pump in the summer to cool your home can be an energy-efficient and cost-effective solution for improved comfort. However, there are certain steps homeowners can take to maximize the use of their heat pumps for summer cooling.

Below are some tips on using heat pump cooling during the summer:

  • Use a high-powered fan: Fans blow air throughout the cooled space, helping circulate cold air and bring the ambient temperature down so the heat pump can work more efficiently. Adding fans to your home to help circulate air can speed up the amount of time it takes to cool a space.
  • Set up a dehumidifier: Dehumidifiers reduce air humidity levels, making your home feel cooler. Since heat transfers through humid air more easily, reducing humidity lowers the air temperature of a space. 
  • Shut the doors and vents in unused rooms: If you only need to cool certain areas of the home, shut the doors and vents to unused rooms. This allows the heat pump to only consume enough energy as needed to keep the smaller space cool.
  • Close the blinds and curtains: Keep your blinds or curtains closed during the day to prevent direct sunlight from entering your home. The sun heats up homes dramatically during the day, so preventing heat transfer can help save energy as your home will stay cooler naturally.
  • Perform summer cleaning: Just as you want to clean and winterize your heat pump as the temperatures drop, you’ll also want to inspect your heat pump in the summer. Make sure the coils are intact and inspect the refrigerant levels. Clean or change the air filters and hose down your outdoor unit to remove any grime and dirt buildup. 

Is a Heat Pump Right for Your Climate?

No matter your climate, you can find a heat pump that’s designed to handle your region’s year-round conditions. Though heat pumps lose efficiency in extremely cold weather, modern cold-climate heat pumps are built to perform under freezing conditions thanks to a few critical design adjustments:

Refrigerant With a Low Boiling Point

Cold-climate heat pumps typically use a type of refrigerant that has a lower boiling point than refrigerants used in standard heat pumps, meaning it will continue flowing and extracting heat from the air even when temperatures are extremely low.

An Inverter Compressor

An inverter compressor is often used in a cold-climate heat pump, which is designed to vary its compressor speed in real-time depending on the temperature conditions. In moderate weather, these compressors run at only a percentage of their maximum speed. When temperatures plummet, the compressor increases speed, drawing sufficient energy required to heat your indoor space.

Efficient Size and Configuration

Cold-climate heat pumps are also configured to maximize efficiency in low temperatures. By designing them to be a certain size for cold climates, these heat pumps can continue supplying heat while remaining energy efficient. Therefore, if you live in a climate that experiences relatively cold winters, switching to a heat pump is still possible by choosing the correct design and model.

Choose MRCOOL for Reliable Heating and Cooling

Heat pumps are practical, energy-efficient and high-performing heating and cooling solutions for residential homes. Households across the U.S. are converting their heating and cooling systems to heat pumps and saving money on their energy bills. 

If you’re considering switching to a heat pump, contact MRCOOL today. Learn more about our heat pump systems, including our GeoCool geothermal heat pump or our Olympus Hyper Heat heat pump. For additional questions, reach out to us online or call us at 270-366-0457.

32 thoughts on “Can a Heat Pump Work in Cold and Hot Temperatures?”

  1. Should one switch the heat pump off when the temperature is ambient. ie the fall & spring or keep it running all the time. In Vancouver climate we have about 5 months of temperate weather.

  2. Hello, I have installed a 3rd Gen 24000 BTU Mr. Cool in my shop in Wisconsin. Well insulated, this unit cools and heats my shop very comfortable. This winter I set the thermostat for 62 degrees F and the garage is staying very comfortable. When the weather occasionally dips down to -5 to 10 degrees F, am I ok to continue to let this unit run. I look at the outside unit and I can see the defrost mode must be working as the unit has deiced with a little frozen water at the lower side but the condenser coils are free from ice. I understand that it is not as efficient at this temp, but it is usually only for a few days, then temp gets back up in the 10 to 15 degree range. As long as I keep and eye on outside unit to make sure its clean and clear of ice, can I hurt the unit? I love the way this works, buts its the only heat source I have in the shop, or do you recommend I add another alternative gas sourced heater?

    1. It should be alright to leave the system working during these sorts of temperatures. The only gas sourced heater that we offer is a gas furnace, which if your shop has ductwork could potentially work. Otherwise, we do not have any sort of gas heating other than furnaces, and ultimately the choice is up to you, if you feel that the heat from a single source is insufficient.

  3. We are experiencing a cold snap in CT. I am advising my son to not try to use Mr Cool 3rd-gen 36k at temperatures below 30 degrees. At what temperature does the efficiency of the heat pump decrease. And how efficient is the Mr Cool heat pump heat in -10 degree temperature, the minimum temperature you reference for this product?

  4. I live in a hot climate in Texas … sometimes 5 months of 100+ degree weather, but sometimes as low as about 5 degrees.

    I worry about having heat during the cold. If I choose a cold weather (artic) heat pump, does that also lower the effectiveness of the heat pump during extreme heat? Does it lower the range? Or just increase the range?

    I’d like a heat pump that can work from between 5 degrees and 120 degrees ideally.

    Just planning for worst cases I’ve seen.

    1. A system like the Universal central heat pump split system won’t sacrifice performance in one direction for the other. This system can heat at 100% capacity at -5ºF, and at 78% capacity at -22ºF. It also has 100% cooling capacity at 115ºF, and 78% cooling capacity at 130ºF. While it may not be as efficient in extreme temperatures, it should still keep you relatively comfortable.

      1. Hi, there!
        Another Texan here. Do y’all have a specific model that you recommend for the climate here? The extreme cold isn’t much of a concern…but the heat? It’s looking like ~100° with another 10° or so tacked on to the index until October!

        1. Our new Central Ducted Hyper Heat is actually great at cooling, too! It can provide comfort in temperatures anywhere from -22ºF to 122ºF. Give us a call at 270-366-0457 for the best assistance with deciding on a new system.

  5. We live in NW Montana, we rarely have temps above 100 Degrees F & rarely have temps less than -20 F. What unit would you recommend for us?

    1. If you’re looking for a central system, you might find that the Universal could be a great fit for you! This system can heat in temperatures as low as -5 degrees Fahrenheit with a 100% heating capacity. It can also heat in temperatures as low as -22 degrees Fahrenheit with a heating capacity of 78%. You can also use auxiliary heat strips in this system for nights that are extremely cold. The Universal can be installed using pre-charged line sets for the simplest possible installation, as well. For more information on this system, please visit or give us a call at (270) 366-0457.

      1. similar q uestion. I am about an hour south of the Canadian border in upstate NY. Avg. temp in January is ~10F (low) but once in a while it is -10, and maybe once/year at -20. So would Universal work for this? And what is the difference between the Olympic and Universal models? Thanks!

        1. While the Universal could produce heat at this temperature, it wouldn’t be the most efficient source of heat, and you may want to support it with another source of heat. The Olympus is a mini-split, so it is not a central system that is connected to ductwork. Depending on what model you get, it will only be able to heat and cool one space, or, if you get the multi-zone version, whichever space an air handler is installed in. Depending on the model, as well, it wouldn’t be able to heat in temperatures as low as the Universal can. Mini-splits are great for adding comfort to a space, though, so if there is a room in your home not covered by ductwork or that is not heated/cooled well, it could be a good option for you.

  6. My diy 27kbtu Mr cool runs fine all day above 30. But definitely blows Luke warm air below 20 degrees. It also switches to defrost mode every 45 mins even though there is no ice on the unit.
    The unit is not freezing up at all but still goes into defrost mode. Checked connections and can’t find any leaks inside or outside. Freon levels are good.. am I missing something?

  7. will the diy 5 zone, 48000btu unit heat when we get the occasional below zero day? what happens at 5 degrees? do i need to get 2 smaller units to make that -13F? i live in nys

    1. While it technically may produce heat at that temperature, it would not be efficient or reliable enough to heat your space with, so on extremely cold days we would suggest relying on a secondary heat source.

  8. I’m getting ready to order a 4th gen mini split HP. The line set distance is 35’ what is the solution for this line set distance?

    1. We have 35′ pre-charged line sets designed for the DIY Ductless Mini-Split, but you can also couple a 25′ pre-charged line set to a 16′ line set with our DIY Coupler Kit to meet that length requirement.

  9. I have a 48K unit on order which will be delivered by 7/26 here in So. Maine.
    Since the line sets come in predetermined lengths, should the excess line going to the ceiling units in the attic be coiled in back of the compressor or inside the attic?
    Note the attic will see the extremes of hot and cold. If you recommend the attic, should the coil lay on top of the insulation or sandwiched in between.
    Also, the compressor will be on a stand away from the house as per specs. Can the top and sides In back of the compressor be covered (with sufficient gap for circulation) to hide the excess coils for aesthetics purposes? Can the cover be placed over the top of the unit to prevent direct contact with snow/ rain?

    1. The excess line set is recommended to be coiled near the condenser but can be coiled wherever fits best for you. If it’s in the attic, then it’s recommended to insulate it. It’s not recommended to cover the condenser, especially the vents, when in use.

    1. It depends on which mini-split you’re talking about. The 12k, 18k, and 24k 4th Gen DIY® Ductless Mini-Splits can heat down too -13ºF, and the 36k models can heat down to 5ºF. Other models, like the Olympus Hyper Heat, can heat even lower than that.

  10. We have the 12K Mrcool DIY unit. It goes into dF mode multiple time a night in 50-60 degree weather. Is that normal? We have not noticed any of our other brand mini-splits go into dF that often.

  11. In the article it says to avoid using the unit continuously. But I am looking to get a unit primarily to reduce the whole-house heating demand of my oil heating system and reduce energy costs. Is there an operating mode that would not use the system continuously even if it is unable to perform the whole-house heating job completely on its own?

    1. Once the system gets your home to the set temperature, it will shut off as normal. This advice is to warn against setting a higher than necessary temperature – in other words, don’t set the temperature so high that the unit will always be on and struggle to reach and maintain the temperature you chose.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Are you a MRCOOL reseller or installer?
For questions about becoming a reseller or representative call 270-366-0457.

Sign Up