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What Size Pool Heater Do I Need?

Pool owners and builders need to think about many variables during the process of buying a pool heater. The owners must calculate the size of their pool and the optimal heater size to match the pool. And that makes a ton of sense. Many stores will try and sell you a heater that may not be viable for your pool. Here, we will discuss what to do and what size of the pool heater you should get.

What Size Pool Heater Do I Need?

Stores will always use the old saying, “the bigger the better.” It may be true; a large pool heater can speed up the heating process faster than the smaller ones. For example, a 400k BTU heater is two times faster than the 200k BTU heater, but also burns gas twice the speed.

However, if you have a pool and spa combination, you will need a larger BTU power pool heater than just heating up a pool. It would be wise to purchase a 30% higher BTU to heat both the pool and the spa than a pool alone, like 300k BTU to a 400k BTU heater. From those examples, we will help you calculate the size of the pool heater you need.


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Calculate the Surface Area of your Pool (length x width)

The first thing to determine before you go out and buy a pool heater is to calculate your pool’s dimensions. Many pool owners believe that the gallon size is the best way to determine the pool heater’s size.

How to Determine What Size Pool Heater You Need

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If your pool’s surface area is large, the heat may escape easily, meaning a larger heater is needed. The heater must be large enough to take care of the surface area of the pool.

The formula to calculate your pool’s surface area is by multiplying the length times the width. For example: If the pool’s length is 10 feet and the width is 15 feet. Calculate 10 x 15, and the surface area is 150 square feet.

Pool’s Surface Area is then Divided by 3

Dividing your pool’s surface area by three will give you the minimal BTU power you will need for that specific surface area. Therefore, continuing from the example above, the calculation is 150 square feet divided by 3, you will get 50 square feet. Thus, for a pool that’s 10 x 15 needs at least 50,000 BTUs.

It is advised to go above the minimum BTUs your pool needs. The pool heater’s primary focus is to heat up the cold areas from the pool’s surface. That’s why a higher BTU count would make it handy.

Pool Heater Sizing

Other Variables to be Considered Beforehand

If a pool that’s 10 x 15 feet without a solar cover, a 100,000 BTU heater would be recommended, but this also depends on your preferences. With a higher BTU count, the heater will compensate for the heat loss, cold weather, and evaporation.

But with a solar cover, you won’t need that much of a high BTU count as it works hand in hand with a heater. Simply a 75,000 BTU heater would be more than enough.

What Size of Pool Heater Do You Need?

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Last Update: 2024-04-14 | Affiliate links/Images from Amazon Product Advertising API

About the author

Hi I’m Alex, founder of HouseholdMe.com and I’d like to say thank you for dropping by. Like most of you, the first thing I look at before buying something online is reviews or buying guides. By reading what other people say will help me gauge whether or not a product is good or not.  I am trying to help people find answers, solve problems, and get inspired.

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