Pool Heater Buying Guide
efficiency, heat pumps are designed to operate continuously so your pool is always at the temperature you desire. Set it and forget it… you won’t have to worry about remembering to turn your heater on Thursday in order for it to reach swimming temperature by Saturday! And because a heat pump is used to maintain a pool’s temperature rather than cycling through on and off periods, savings are also obtained because heat pumps need less BTU’s.
And there are actually models that will cool your pool water in the really hot summer months! So when the air temperature hits triple digits, your pool will be refreshingly cool.
The following formulas are provided to help determine the correct size heater needed to heat and maintain a comfortable temperature in a given size pool.
HOW TO CALCULATE POOL GALLONAGE
Note: Average depth is determined by adding the depth of the shallow end to the depth of the deep end and dividing by 2.
For Round Pools:
Gals. = Diameter x Diameter x Avg. Depth x 5.9
For Oval Pools:
Gals. = Length x Width x Avg. Depth x 6.7
For Rectangular Pools:
Gals. = Length x Width x Avg. Depth x 7.5
For Kidney Shaped Pools:
Gals. = Length x Avg. Width x Avg. Depth x 7.0
CALCULATING NECESSARY HEATER OUTPUT
FORMULA:
POOL GALLONS X 8.33 X DESIRED TEMP. RISE / 24 HOURS =
HEATER BTU'S PER HOUR REQUIRED TO HEAT UP THE POOL
EXAMPLE:
30,000 gallon pool @ 55 degrees, heated to 75 degrees
30,000 x 8.33 x 20 = 4,998,000 BTU'S / 24 hours = 208,250 Output BTU'S per hour
The example above shows that 20' x 40' pool with an average depth of 5 feet with a heater producing an output of approx. 210,000 BTU's would require 24 hours to raise the temperature of the pool 20 degrees; hence a filter with an output of 400,000 BTU's would do the same job in about 12 hours. Note the BTU's are shown as an output number. Many heaters are rated at input BTU's, meaning you need to adjust for heater efficiency. If you cannot determine the efficiency rating of a heater, an acceptable rule of thumb would be to use 85%. This means a 400,000 BTU heater would produce 340,000 output BTU's.
The above formula gives you the needed minimum BTU's needed to initially heat a pool to the desired temperature in 24 hours. This should be used as a minimum figure to consider when selecting a pool heater.