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Heater Sizing Guide

Selecting the Correct Size Heater for Pool and Spa

Many factors depend on how you heat your swimming pool – installation costs, how often you use your pool, size, location and climate.  This guide will show you how to calculate the minimum heating capacity for your pool based on your specific application and provide you with the information you need to make an informed decision on the best and most economical way to heat your pool.


Step 1

Determine the Ideal Water Temperature

How warm do you want the pool water and how fast do you want to raise the temperature? Most pool owners consider 75 – 85 degrees Fahrenheit to be adequately comfortable.


Step 2

Determine Average Ambient Temperatures

Calculate the average temperature in your area during the coldest month you intend to use it.

Important: Consider other weather conditions, including humidity, wind chill, and night temperatures. If you live in a dry climate, if wind speeds are high or temperatures drop at night, you should plan for a larger heater.

Step 3

Calculate Temperature Rise

Subtract the average temperature from your ideal temperature.  The result is the number of degrees your heater will need to heat a pool in order to make it comfortable.

Step 4

Measure Pool Capacity

Find the surface area of your pool in square feet.  Note the length, width, depth, gallons and shape.

Use our Pool Surface Area Calculator

Step 5

Choose a Heating Condition

Decide how you plan to use your pool and how often.  There are two heating conditions to choose from; heat from cold or maintain the desired temperature.  If pool use will be on a daily basis, you may wish to keep it heated continuously.  Heating from cold will require raising the water from cold to the desired temperature.

Multiply the pools surface area in feet by the Temperature derived in Step 3.  Then multiply that figure by eleven.  The result is the approximate BTU/hr. (British Thermal Units per hour) the heater requires in order to heat your pool properly.

Important:  A pool will gradually lose heat due to evaporation and may cause your pool to take longer to achieve desired temperature.  Investing in a pool cover will reduce heat loss by up to 80 percent.

Step 6

Choose a Heater Type

There are a variety of pool heating methods available in a full range of capacities and models. Remember that a higher capacity heater will be more efficient and use less energy to heat your pool.

> Compare different heating options

Need help?

If you need assistance, we're here for you.

A trained pool heating professional can perform a proper sizing analysis for your swimming pool to determine the correct pool heater size that you need.  We’ll provide you with product features and details on our complete line of heat pumps and heaters.

> Get your free analysis today!


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