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Pool Heater Sizing Guide

How to Choose the Correct Size Heat Pump or Heater for Pool and Spa

Pool heater sizing is measured in BTU’s (British Thermal Units.) The higher the number of BTU’s, the quicker you can heat your pool water. To find out how many BTU’s are required for your specific application, you must calculate the surface area of your pool; your geographic location; ambient temperature; and the environmental conditions such as shade or wind. Whether you retain heat with a solar cover, also determines sizing requirements.

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.

Important Reminder:

A pool heater can never be too big, but buy a pool heater that isn't big enough and you'll never be satisfied.

When selecting your pool heater, always choose a heater rated somewhat higher than your actual pool surface area and desired temperature rise required. There is no such thing as “oversizing” a pool heater. The larger the BTU output of the pool heater you buy, the quicker it will heat your pool water. This means less run time on the heater and a longer overall heater life span. You will always be glad you opted for the larger pool heater.

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.

Six Steps to Sizing a Pool Heater

Step 1 Determine 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 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.

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. carries heat pumps, gas pool heaters, propane pool heaters, electric spa heaters and solar pool heaters to help make your pool water temperature comfortable any time of year. Remember that a higher capacity heater will be more efficient and use less energy to heat your pool.

Compare different pool heating options

Let a pool heating professional do the work.

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. If you have questions, please feel free to call us at 1-800-741-9956. Our team of friendly pool experts will answer any questions you may have and offer technical advice in selecting the model that is right for your pool.

Get a free pool heating analysis today!