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All You Need To Know About Pool Heaters

In Maintenance and Repair by Frisco Pool BuilderLeave a Comment

If you have a pool or have been thinking about installing a pool, you probably have plenty of questions. And undoubtedly, one of those questions probably has to do with pool heaters. Right?

No worries!

Here are the most commonly asked questions about pool heaters and what you need to know to make an educated decision about whether or not installing a pool heater is the right decision for you.

1. What Size Heater Does Your Pool Need?

When trying to determine what size pool heater you might need, you should first think about how you will be using your pool. If you will be using your pool intermittently, you will probably need a larger pool heater because a gas heater will only raise the pool temperature about one to two degrees per hour. But if you want to maintain your pool at a consistent temperature using a thermostat, then a smaller pool heater should suffice.

Here is an at-a-glance table you can use to determine what size gas heater your might need for your pool. And don’t hesitate to contact your pool company for a more detailed explanation of any questions or concerns you might have.

Gas Heater Size Gallons of Pool Water Surface Square Feet of Pool
100K – 200K BTUs 1K – 10K Gallons up to 300 sq ft
200K – 300K BTUs 10K – 20K Gallons up to 500 sq ft
300K – 400K BTUs 20K – 40K Gallons up to 800 sq ft
400K + BTUs 40K – 80K Gallons up to 1200 sq ft

2. How Much Will a Pool Heater Increase Your Electric Bill?

The utility cost of running a pool heater will depend on the type of pool heater you have.

Propane pool heater. These use about one gallon of propane per hour for every 100,000 BTUs. The cost of propane varies, but you can check the rates on the website.

Natural gas pool heater. These use about one therm per hour for every 100,000 BTUs. The cost of natural gas varies, but you can check the rates on the website.

Heat pump. These use about 5,000 watts or five kilowatts per hour for every 100,000 BTUs. The cost to run an electric heat pump varies by state, but you can check the rates for Texas on the website.

3. How Long Will It Take To Heat Your Pool?

Typically it takes about half a day to heat most average size pools. However, here is a formula you can use for a more exact calculation based on your particular pool.


Take the number of gallons of water in your pool x 8.34 = the number of pounds of water in your pool.

Then divide that by the BTU size of your heater to get the number of hours it would take to raise the temperature one degree Fahrenheit.

Then all you have to do is figure out how many degrees you want to raise the temperature of the water and multiply that by the amount of time it takes to raise it one degree.

So, for example, let’s say you have a 20K Gallon Pool and a 300K BTU heater.

20,000 x 8.34 = 166,800 lbs of water.

166,800 lbs / 300,0000 BTUs = .556 hours/degree.

So, if you want to raise the temperature of your pool 10 Degrees it would take 10 degrees x .556 hours/degree = 5.56 hours.

4. Where Should You Buy a Pool Heater?

The best way to decide on where you should buy a pool heater is by first talking to your local pool company. They will be knowledgeable on all the latest equipment and which products would work the best for your particular situation. They will also be able to provide you with a quote for installing the pool heater of your choice. However, if you’re a DIY kind of person, there are plenty of places online you could buy a pool heater as well.

5. What Are Typical Causes of a Pool Heater Not Working?

Pool heaters are one of the most complicated pieces of equipment on your pool. So troubleshooting and repairing a pool heater can be tricky, not to mention dangerous because you’re dealing with gas or propane. There are so many variables it would be difficult for anyone other than a pool expert to properly diagnose and fix a pool heater problem. That’s why it’s always best to hire a professional.

Here are some of the most common causes of a pool heater that’s not working.

  • Pilot light issues.
  • Either the gas supply, plumbing, or filter valves aren’t open.
  • Low gas pressure or improper venting.
  • The thermostat is out of calibration.
  • A faulty high-limit switch.
  • The heater isn’t getting adequate air flow due to external bypass, reversed water connections, or a pressure switch that needs adjusted causing the heater to cycle on and off before reaching the desired temperature.
  • Problems with the heat exchanger.
  • Clogged burner openings.
  • These are just a few issues that could cause a pool heater to malfunction. It’s best to contact your local pool expert for an exact diagnosis and estimate to have it repaired.

Got Pool Problems?

We have solutions! The Foley Pools family has been a respected member of the community since the 1950s. And we have the expertise to properly diagnose and repair any pool problems you might have. Contact us today and let us take the burden of pool repairs off your plate. We'll do the heavy lifting so you can sit back and relax!

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