The Ultimate Guide to Understanding How Pool Heaters Work (2024)

What Do Swimming Pool Heaters Do?

To keep it simple, both natural gas heaters and electric heat pumps will give you the same end result: warmer water. They operate a bit differently. A Natural gas heater uses gas while a heat pump uses both electricity and the outside air to function to give us our desired temperature. As the swimming pool water is drawn from your skimmer and/or main drain, the pool pump pushes the water through your various pieces of equipment. You definitely have a swimming pool filter as this is where the water gets cleaned. You may also have a salt system, in-line chlorinator and, you guessed it, a heater. The warm water is then returned back into the swimming pool through the return inlets. To see how heaters are sized, check it out here

Sizing a swimming pool heater involves determining the appropriate heating capacity or output needed to effectively heat the pool water based on several factors, including the pool's volume, desired temperature rise, climate, and other variables.

So you are thinking of purchasing a heater. Maybe yours cannot be repaired. Maybe you want a more efficient piece of equipment. Maybe you want to extend your swimming season. Maybe you are building a new pool. Whatever the reason, you may be wondering which type of heater is right for you. We are here to help. There are two major types of heaters. Gas heaters (either propane or natural gas) and electric heat pumps. For the sake of this article we will be talking about natural gas and electric heat pumps. Just keep in mind propane gas is an option, although not very popular except maybe in rural areas.

The Ultimate Guide to Understanding How Pool Heaters Work (1)

Natural Gas Heaters

Natural gas heaters work in all types of climates. They utilize natural gas to heat the water and do not rely on the outside temperature. You will either need to have existing gas lines or have gas lines installed to accommodate a natural gas heater. If you are looking for a quick way to heat your swimming pool or spa then a natural gas heater may be for you as they heat more quickly than a heat pump. They are more efficient in this regard.

Pro Tip: The size of the heater you purchase is limited to the size of your gas line as well as how long the gas line run is.

How quickly do they heat? This depends on many factors such as the temperature of the water and how many degrees you want to heat it. It also depends on the size of your body of water. This is measured in gallons. When we talk about heater “size” we are typically not talking about the footprint, or dimensions of the heater, but the heat output. This is measured in British Thermal Units (BTUs). Dimensions are also important. Especially if you have limited space on your equipment pad. The larger the heater (the higher the BTU), the more quickly you can expect your water to be heated.

Natural gas heaters nowadays come in what is known as a LoNox model. This makes for a more efficient machine. They come in a variety of brands and BTUs. They can also be more affordable than an electric heat pump to purchase. It all depends on where you shop.

Pro Tip: Always go with the largest BTU your gas lines can accommodate. While pricier up front, you will get that money back as you save on operating costs.

Electric Heat Pumps

Electric heat pumps are good for climates that do not drop below 45-50 degrees Fahrenheit. This is because they rely on the outside air to heat your water. Swimming pool heat pumps run on electricity–not gas. They tend to have a lower operating cost annually versus a natural gas heater. They will tend to last longer as well! They are efficient and friendly for the environment.

Heat pumps function by extracting the outside air and utilize a compressor to increase the heat of the water as it passes through. Typically, 3-5 degrees Farenheit each time. Heat pumps are not designed for quick heating. In fact, you can expect to run your heat pump 24-72 hours to get to your desired temperature. Like a natural gas heater, this depends on gallons, current temperature, desired temperature, BTUs and with a heat pump, the outside temperature.

Heat pumps are used to maintain your water’s temperature. That is why they need to run for so long. They are also measured in BTUs. They are also slower at increasing the water’s temperature. Heat pump usage is measured in watts or kilowatts. You can check out your electric bill to see your price per watt/kilowatt.

Pro Tip: If you have solar on your home, a heat pump is a great investment for you. It can actually earn you money if your power is purchased back by your utility company.

If a Heat Pump is Right for You

Heaters are expensive. That is because of all the fun you will have if you want to put a positive spin on things. I am a positive type of gal. If you were to go to your local swimming pool supply store either a gas or electric heater of a good size will run in excess of $4,000. Heat pumps tend to work a bit higher. I recommend going with a name brand and efficient heater.

You can actually get a name brand heat pump for MUCH lower than you might think. The Nationally known, ComforTemp, makes an efficient high quality electric heat pump. When I say quality, I mean amazing quality! They are fast acting and energy saving. They also make less noise. The best part, in my opinion, is the fact that they self diagnose themselves for easy maintenance. Why sacrifice quality for price, I say! You can have both. Check them out here. See you poolside!

The Ultimate Guide to Understanding How Pool Heaters Work (2024)


What is the most efficient way to run a pool heater? ›

Every degree you raise the temperatures increases energy costs dramatically; keep water warm, but not spa-warm. Lower the thermostat when the pool isn't being used – If you don't plan to use the pool for a few days, cover it and drop the thermostat to 70 degrees. For longer periods, shut the heater off.

Should I leave my pool heat pump on all the time? ›

While running your heat pump non-stop can ensure a consistent temperature, it's essential to balance the benefits against the potential increase in energy bills. That being said, it's more economical to maintain a regular heating schedule than to only power up when you're ready to dive in.

What temperature should I set my pool heat pump at? ›

The water temperature you desire for your swimming pool not only affects the size of the pool's heater, but also your heating costs if use a gas or heat pump pool heater. Pool water temperatures typically range from 78ºF to 82ºF. The American Red Cross recommends a temperature of 78ºF for competitive swimming.

Is it cheaper to leave a pool heater on all night or shut it off at night and restart it in the morning when the pool temperature drops 10 F? ›

You Should Never Leave a Conventional Pool Heater on Overnight. Although electricity and gas costs can vary wildly depending on where you live and how much energy usage is typical for your area, heating pools with conventional heaters can be costly if time is not taken into consideration.

Is it better to run the pool heater during the day or night? ›

Keeping your pool heater running overnight will prevent rapid heat loss and stop your heating units from working double-time to compensate for it. If you expect overnight swimmers and partygoers on your pool deck, keeping your pool warm while the sun is down is the way to go.

How long should a pool heater take to heat a pool? ›

What type of Swimming Pool Heater do you use? If you're using a gas pool heater, it will typically take about 8-12 hours to heat up your swimming pool. Gas heaters are actually the fastest option for pool heating since they use natural gas to generate heat in cold temperatures.

At what temp does a pool heater stop working? ›

If it is too cold outside, usually less than 60 degrees Fahrenheit, it may be too cold for your heater to run. While some pool heaters can operate in temperatures ranging from 30 degrees Fahrenheit and up, not all do.

Does water run through a pool heater when not in use? ›

Water circulates through the heater core all the time the pump is running, whether the heater is on or off. If the heater springs a leak, you have to shutdown the pump, which stop waters circulation, filtering and chlorinating your pool.

Does pool heat faster with pump on or off? ›

With the pump turned on, the heating process is normally faster. Keeping the pump turned on while heating helps to maintain a constant temperature distribution, minimizing cold areas that can develop with insufficient water circulation.

Do pool heat pumps use a lot of electricity? ›

Heat pumps will use around 5,000 watts or 5 kilowatts per hour per 100,000 BTU's. For a typical size 100,000 BTU heat pump, that's 5 kilowatts per hour. The average for electricity in our area runs $. 16 cents per kilowatt hour.

How do I get the best out of my pool heat pump? ›

How to Maintain My Swimming Pool Heat Pump?
  1. Schedule Regular Maintenance. ...
  2. Keep the Heater Area Clean. ...
  3. Check the Water Flow. ...
  4. Monitor the Water Chemistry. ...
  5. Address Problems Promptly. ...
  6. Drain the Water and Prevent Frost Damage During the Winters. ...
  7. Cover the Pool to Keep the Temperature From Dropping Dramatically.

What is the most efficient way to run a pool heat pump? ›

Use your heat pump during warmest time of the day

Since heat pumps get their heat from the air, you will greatly increase its efficiency if you run it during the warmest part of the day. Cutting energy usage with careful timing could save you money.

What is a comfortable pool temperature? ›

Safety and Comfort

For example, Mayo Clinic suggests that younger children and the elderly will generally need warmer temperatures ranging from 84°F to 94°F, while a comfortable pool temperature for adults is 85°F to 89°F. If you are swimming for fitness, cooler temperatures of 78°F to 84°F are recommended.

What is the best position for a pool heat pump? ›

Choose a wide-open outdoor space that provides plenty of fresh air. Allow sufficient clearance on all sides of the pool heat pump for service, repairs, and cleanup. Keep the pool heat pump away from gutters, sprinklers, and other water sources. In particular, check that water is not running off the roof onto the unit.

What is the most efficient schedule for heating a pool? ›

Heat the pool only when you plan to use it.

Keep the pool water temperature in the low to mid 70s, then turn up the heat an hour or so before you plan to use the pool. Turn it back down and put the pool blanket in place to hold the temperature between swims.

What's the most cost-effective way to heat a pool? ›

One of the most cost-effective heating methods for retaining heat in a swimming pool is installing a solar cover, keeping water up to 10 degrees warmer than with only a heater. The root cause of heat loss in a pool is evaporation.

Does a pool heater use a lot of electricity? ›

Pool heat pumps are specifically known for their energy efficiency, so expect a lower energy bill of $50-$150 per month (depending on the size of your pool).

Is it cheaper to heat a pool with gas or electric? ›

Gas is typically cheaper than electric when it comes to the initial cost. However, it relies on the prices of natural gas and propane, meaning that despite the equipment being a bit on the less expensive side, the cost to operate a is usually more expensive in the longer run.

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