Everyone loves going for a good swim, but not everybody loves the temperature of the water once they get in. Most homes don’t have the room or budget for a Jacuzzi, so the next best accomodation is to purchase a heater for the pool. But many homeowners are left pondering, “what size pool heater do I need?” This article aims to answer that question and post a few helpful hints along the way.

”Swimming is my passion and something that I love.” - Natalie du Toit

How to Size Your Pool

Here's how to heat your pool the smart way
Heating you pool this summer! Source: HGTV

The long story answer is: you should get a professional. Otherwise you’ll need to take in various factors when determining how large your pool heater should be.

The heater is, of course, sized to the surface area of the pool, but also in accordance with the difference between the water temperature and air temperature. Furthermore when it comes to outdoor pools, wind exposure, humidity levels, and cool night temperatures are also all factors.

Here’s a good rule of thumb guide for sizing a pool heater:

  • Determine the temperature that you want your pool to heat to
  • Keep in mind what the coldest water temperature will be during the season
  • Subtract the coldest temperature from the desired temperature, this determines the “rise” of the pool’s temperature
  • Calculate the pool’s area surface in terms of square feet
  • Use formula: Pool Area x Temperature Rise x 12
  • Use the number you get to determine which pool heater you need (see next section)

Total Output

How to heat an above ground pool
Here's what heating an above ground pool looks like. Source: The Minimalist

Pool heaters are rated by British thermal units, or Btu’s, to determine their power output. Some standard Btu measurements are 75k, 100k, and 125k systems. Additionally, the same units can also be measured in horsepower, with the respective measurements of 3.5hp, 5hp, and 6hp.

Using the equation above will determine which of these heaters you’re going to need for your pool. This is how to start narrowing down answers to the question, “what size pool heater do i need?”

What Kind of Pool Heater?

There are even solar panel pool heaters
What a solar pool heater looks like. Source: Amazon

Did you know you have quite a selection of pool heaters to choose from for your home? Of course there are electric pool heaters, but there are several options you should be aware of before committing to any particular type. There are the different energy types that pool heaters can be powered from. Here is a short list of the available types of pool heaters:

  • Solar pool heaters
  • Gas pool heaters
  • Pool heat pumps
  • Electric pool heater
  • Mat heater

In conclusion, attempting to size one’s own pool for a heater is a difficult task, and one best left up to professionals. This is especially true for commercial pool heater sizing. So if you’re in doubt at all, always call a professional. Swimming in your own pool shouldn’t stress you out.


Trying to figure out what heater you need? Looking for more ideas in terms of swimming pool additions? Get in touch with a contractor today!

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