August 18, 2025
Propane Pool Heaters – How Do They Work?
Propane Powered-Pool Heaters
It’s many homeowners’ dream to add a pool to their outdoor living amenities. Unfortunately, New England has a short swimming season- which drastically cuts down the number of days in the year that your new investment can be enjoyed. This is where pool heaters come in. By adding a heater to your pool system, you can keep your pool open longer and enjoy it more- improving the return on your investment!
Heating Water
Raising the temperature of water takes a lot of energy, and the more water you are trying to heat, the more energy is needed for that water to get warmer. This is due to water having a high specific heat.
What is specific heat? Specific heat is a measure of the amount of energy needed to raise the temperature of a mass of liquid. A high specific heat means that a high amount of energy is needed to increase the temperature.
Calculating BTUs
BTUs (British Thermal Units) is the unit of measurement used in heating and cooling. Pool heaters come in
a variety of BTUs, much like you see in air conditioners. The higher BTU on an air conditioner, the more space it is rated to cool. It is the same with pool heaters, except the BTU will indicate the volume of water the pool heater is rated to heat, and by how much.
There are several ways to calculate the BTU you will need for your pool, but the temperature differential method is a simple and reliable one.
Based on this formula, to heat a 512 sq ft pool holding 22,980 gallons of water to 10° above its existing temperature, you will need at least 229,800 BTUs. This is before considering a climate factor (wind, shade, etc.), which could increase the needed output by up to 10%.
Try it at home and see what you come up with.
How Long Will It Take to Heat My Pool?
This will depend on the size of your pool, how much warmer you want the water to get, and the BTU of the heater you are using. Let’s stick with data from the example above and go from there!
We have 22,980 gallons of water, we want to increase the temperature of the water by 10°F, and our pool heater is at least 229,800 BTU.
Here’s the formula:
Heat Time = (Gallons of Water x 8.33 x Desired Temperature Increase) / Heater Output Power
Heat Time = (22,980 x 8.33 x 10°) / 229,800 BTU
Heat Time = 8.33 hours
If you were to upgrade your pool heater to 400,000 BTU, this would decrease your heat time by almost 50%!
While it may be tempting to spend less on a lower BTU heater, investing in a higher BTU heater is clearly a worthwhile endeavor.
How Do Pool Heaters Work?
Propane-powered pool heaters burn fuel in a combustion chamber, which generates heat. That heat is then transferred to a heat exchanger, warming the pool water as it circulates through the heater. See the diagram below.
Why Should I Use a Propane-Powered Pool Heater?
Propane gas pool heaters heat water quickly so you and your family can enjoy your pool for longer throughout the year, even after ‘pool season’ is over because they will continue to work well even when it gets cool outside. This also makes propane-powered pool heaters ideal for heating hot tubs since they are frequently used year-round.
On top of its high efficiency as a heating source, propane is also non-toxic. This makes it more friendly to the environment than many other heating options. Though the up-front cost of choosing a propane pool heater may be higher than other options, its long term cost-of-use often makes this option more cost effective.
What If I Don’t Already Use Propane At Home?
Don’t worry about anything! There are many pool owners who use propane to fuel their pool heater that don’t use propane inside their home. There is no need to connect the propane to any other appliances. A member of our team would be happy to schedule a no-obligation consultation at your home to help you decide the optimal place for the propane tank and pool heater, as well as be able to talk with you about expected usage based on how frequently you plan to use the heater and when. Contact Palmer Gas & Oil today at info@palmergas.com or (603) 681-2260 to schedule your consultation today!