How to Choose the Right-Sized Heater for Your Pool

One of the great things about living in the Tampa area is that you can use your backyard pool almost all year long – especially if you’ve invested in a pool heater. If you’re still thinking about purchasing a heater or adding one to your new custom pool, you may have found that choosing the right size for your needs can be a bit of a challenge.

If you choose a heater that is too small, you won’t be satisfied with its performance. Undersized pool heaters take too long to heat the pool and have difficulty keeping it at the desired temperature. On the other hand, choosing a heater that is too big will cost you, both in terms of the initial price and ongoing energy costs.

So, how do you choose the right-sized heater for your needs? Start by considering these important factors.

Pool Heater Size Needs: Important Variables to Consider

While your pool’s volume and surface area are two of the primary factors that influence the size of the heater you’ll need, you also need to consider the climate where you live and how you plan to use your heater. Here are a few questions to ask yourself:

  • What is your ideal water temperature?
  • What’s the average low temperature during the months when you plan to use your heater?
  • Do you plan to use your pool at night and/or during the colder months?
  • Are you heating a spa/pool combo or a pool on its own?
  • How quickly do you need your pool to heat up?
  • Do you have a pool cover or solar blanket?

Generally, the harder you expect your pool heater to work, the larger size you’ll need. If you have a solar blanket or a pool cover, you may be able to purchase a slightly smaller heater, since the cover will hold heat in and make it easier to maintain the water temperature.

Calculating Your Minimum Pool Heater Size

Determining the exact sized pool heater you need requires some fairly complex calculations. However, you can quickly estimate your minimum heater size by completing the following steps.

1. Multiply your pool’s length by its width to determine the surface area.

For example, if you have a pool that measures 15 feet by 30 feet, the surface area is 450 square feet.

15 x 30 = 450

2. Divide your calculated surface area by 3 and multiply the result by 1,000.

The answer indicates the minimum BTU you need for your pool’s size. Continuing with the example above, a 15-foot by 30-foot pool needs a heater that is at least 150,000 BTUs.

450 sq. ft. / 3 = 150
150 x 1,000 = 150,000 BTUs

It’s critical to remember that this is the absolute minimum size you need. In most cases, you’ll want to size up to make sure the heater works quickly and can easily maintain your desired temperature.

The following chart provides some general size recommendations for gas pool heaters. You’ll want to size yours up or down depending on your answers to the questions listed above.

Pool SizeRecommended Heater Size
16’ x 32’250,000 BTU
18’ x 36’325,000 BTU
20’ x 40’400,000 BTU

Consult with Our Experts

If you’re still not quite sure what size pool heater you need, your best bet is to consult with an expert. The custom pool installation professionals at Swim Inc. can help you with everything from pool design to choosing the perfect filter, heater, features, and more. Contact us today to schedule a consultation.

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