Normally, heat pumps are sold for use in the summer season only. Yes, all the manufacturers state that they will work in ambient temperatures from 0-5 deg but will have minimal heat output, and realistically, at these temperatures you will be unlikely want to be swimming. Ideally, a heat pump should not be switched on until the ambient air temperature has reached 15-20 deg.

Heat pumps are ideally suited for heating your pool in the summer season only (May – September). However, with various climate changes that we have been experiencing in recent years, we have had reports from our customers that they have been running their heat pumps from April to late October!

Unfortunately, sizing the heat for your swimming pool is not an exact science due to so many variables such as the thermal value of the pool structure, wind speed, water velocity, water table etc and if a heat retention cover has been applied.

Therefore, heat pump manufacturers’ base their calculation on the amount of heat (kW) your pool is likely to loose on an hourly basis. You will see that on some pool sizes we recommend two sizes of heater. If your budget allows, it is desirable to buy the larger size, due to it being more cost effective, efficient thus resulting is a quicker heat up time.

Swimming Pool Heat Pump Size Guide Chart

The sizing chart below assumes the following:-

  • 15 deg C / 59F ambient air temperature (Realistic for start of season)
  • Average wind speed 2.5 metres per second
  • Desired water temperature 30 deg c / 86F
  • Average pool depth 1.5m / 5ft
  • No water table surrounding pool structure
  • Minimum running time 10 hours per day
Pool Size – Imperial Pool Size – Metric Heater
Length (ft) Width (ft) Approx Gallons Length (M) Width (M) Approx Litres Minimum size heater required (KW) Optimum size heater required (KW)
24 12 8550 7.32 3.66 38868 9/10 14
26 13 10034 7.92 3.96 45616 9/10 14
28 14 11638 8.53 4.27 52904 9/10 29
30 15 13359 9.14 4.57 60732 14 29
32 16 15200 9.75 4.88 69099 29 29
40 20 19238 10.97 5.49 87454 29 29
40 20 23750 12.19 6.10 107968 29 29

For further information about how heat pumps work please click here.

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To see our swimming pool heating section please click here.