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Is It Too Cold To Use My Swimming Pool Heat Pump?

Is It Too Cold To Use My Swimming Pool Heat Pump?

Is it Too Cold To Use My Swimming Pool Heat Pump?

One of the main advantages of purchasing a heat pump for your pool is that it allows you to extend your swimming pool season, and to enjoy your pool even in the winter months. This is especially helpful if you live in an area where temperatures drop dramatically during the winter. But just how cold is too cold to run your heat pump before it can no longer heat your pool, or worse, gets damaged?

In this article, we will answer that question, and provide you with some information to help you get the most out of your unit.

Heat Pumps
A “heat-only” swimming pool heat pump—designed to only heat the water and not cool it—can work effectively down to the mid to lower 40s. However, the ambient temperature greatly affects the ability of air-source heat pumps to produce heat. The colder the air, the less heat your heat pump will be able to produce. You can extend the lower temperature limit for your heat-only swimming pool heat pump by winterizing it when the temperatures drop.

Reversible Units
Some units, like the AquaCal ICEBREAKER™, are “reversible” and provide heating or cooling. Reversible units can also operate when the outside temperature is down to the mid to lower 20s, although that does not necessary mean it can heat the pool to 80° on a 20° day. As a rule of thumb, the highest water temperature rise you can get from an air-source heat pump under ideal conditions is 30°. For example, if the outside temperature is in the 40s, you can expect the pool to warm up only to the 70s.

Commercial Heat Pumps
Not many heat pumps can handle the demand of heating commercial swimming pools. Yes, you can install a number of residential heat pumps to create enough BTUs to heat any size pool, and you can use heat-only or reversible heat pumps. There is, however, a reversible unit on the market that has the ability to create almost a half a million BTUs with just one heat pump: The Great Big Bopper (GBB). To read more about the GBB, please click here.

The are also geothermal heat pumps that are produced for commercial applications. For more information on geothermal heat pumps pool heaters, click here.

These options will help you enjoy your swimming pool even in the colder months. Of course, knowing the limitations of your unit, as indicated by the manufacturer, is the most important step in helping it run efficiently and without being damaged.

Regardless of the when Old Man Winter decides to visit, you can extend your swim season beyond…well…swim season!

If you have any questions, please do not hesitate to ask us, or leave a comment below.


This Post Has 24 Comments
  1. Out here in southern california it gets really hot during the summer, but during the winter its not comfortable to go in the pool. Thanks for informing me a little bit more about how I can enjoy my pool during the chilly season, which is almost here by the way. Thanks!

  2. I have a the Icebreaker model SQ 156R. We have been having temperatures in the teens at night and not getting above freezing during the day. It’s 24 degrees now and I turned the heater to a set point of 40 degrees. The Mode indicates “Heat” but it’s not heating. Is there a minimum temperature for the heater to run? Thank you

    1. Hi Mike,

      Heat Pumps operate best with warmer ambient air temperatures, i.e. high 50F’s and over 60F, because it uses the ambient air as its heat source. When you run a heat pump at 24F it will start icing up and go into defrost mode to melt the ice. At 24F the unit will spend more time defrosting than transferring heat to your pool. If you have any questions, please call us at 727-823-5642.

  3. Great service ……on time and very polite service person Josh Fort. He explained the concern and made the correction…… this is a very customer driven company. I recommend them very highly. Ask for Josh. He is great.

  4. I just purchased a house with this awesome piece of equipment; the water is quite cold; how long does it generally take to heat average size pool. Thanks so much for your time.

  5. Live in coastal Connecticut and had an icebreaker installed on my 17,000 gallon gunite last season. My pool faces south but i was able to maintain 80 F degree water until the end of October. I started loosing efficiently due to evaporation in early Oct but starting using a liquid solar cover which drastically decreased the evaporation and improved efficiency.

    My experience is exactly as this Aquacal states, if ambient temperatures are above 40 F and wind or evap arent a factor there are no problems heating and maintaining temperature.

    At the end of October, we started having nights below freezing. The icebreaker will automatically defrost and then start hearing again but the efficiency is too low to battle temperatures in CT that late in the season.

    However, i can maintain 80 to 90 F water from begining of May to end of October by extending run time and using liquid solar blankets. If it works for me in CT, should work in most places where folks own swimming pools!

  6. Hi, I have an Aqua Cal heat pump installed in Mexico city. For 2 years the heat pump was working ok. But since october of last year the heat pump has been freezing . The supplier has checked several possible reasons, they even change some parts and they are trying with an other location with more space, air and sun.

    Now that the heat pump is in the new location the heat pump is not able tho warm the pool more than 77F / 25C.
    Its impposible to achive a decent temperature. And just start to freeze again. The supllier told us part of the problem is the cold months.

    The temperature in these days 48F – 76F. / 9C – 24C.

    Could this be a reason for the problem? Ist been so long since the heat pump start to fail so the pool is now closed.

    1. Hello Selegna,

      A heat pump can start icing when run in lower ambient air temperatures, i.e. 40’s & 50’s DEGF. However, they are designed to defrost. Once the defrost cycle starts and the ice is melted they should go back to heating. Does the heat pump eventually melt the ice on the unit? Are you running the heat pump 24 hrs/day? During the warmest part of the day, does it look like the heat pump is raising the pool temperature? If you would like to contact us directly to discuss please call us at 727-823-5642 or send your contact information to

  7. I have an indoor 10,000 pool, the room is 20×40 with 30 foot ceiling sloping to 8 feet. If i put the heat pump in this room, wont it just take the heat that has escaped from the pool and put it back into the pool?

    this room is not heated by a furnace, removing the cover from the pool heats the room up very fast !!!

    1. Good afternoon Andrew-

      Running the heat pump indoors may actually cool the room down. The air coming off the fan during operation is 9-12 degrees colder than the ambient temperature. Proper CFM airflow and ventilation are important for an indoor installation. If the air off the fan isn’t vented out of the room, the colder air will begin to recirculate through the evaporator reducing BTU output and if there isn’t adequate airflow across the coils it may cause an LP error code. Contact the factory at 727-823-5642 for more information regarding indoor installations.

      Hope this helps!

    2. This will work, and will also dehumidify, but it will pull down the room temp down, so the heatpump will perform like it’s in winter! So have max ventilation in the room to stop it pulling out all the heat energy. So the room might get colder than ambient!

    1. Good afternoon Dave-

      There are a number of factors to consider when heating a pool so the answer to this question will vary depending on the circumstances. Generally speaking, if the night time lows are in the 50’s & 60’s and inclement weather isn’t a factor(wind, rain, cold fronts, etc.) you shouldn’t have any problems achieving an 80 degree water temperature.

      Some factors to consider when heating in these temperatures would be your geographical location, the duration of the cooler temperatures, runtime of the pool circulation pump, blanketing, if the unit has a hot gas defrost and the temperature rise you are trying to achieve. The cost estimator program on our website can help determine if you will be able to heat the pool in a particular month and location. The program uses the average monthly temperatures from weather data compiled over the past 30 years and covers the United States as well as many international locations. Once a city and state are selected the monthly temperatures will populate. The temperatures in red indicate the month(s) that the unit will not efficiently heat. The program does not take indoor installations, solar or a gas assist into consideration and is based on a typical outdoor installation. The months shown in black indicate the average temperature is conducive for heating. Since the estimator program is based on averages, spikes in weather conditions cannot be factored in.

      If you need more detailed information on heating please contact Aquacal technical support.

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