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What size pool heater do I need?

Put in your pool's volume and surface area and pick a heater type. You get the size, the models that fit, and how long each takes to warm the water.

Updated · How we check our numbers

These are example numbers. Put in yours.

Your pool

gal

The pool volume calculator works it out.

sq ft

Length × width for a rectangle.

The heater

Heater
Air temperature you'll heat in
°F

From where the water is to where you want it.

Heat pump size

95,200 Btu/h

California's code sizes a pool heat pump to add 10°F in 17.5 hours or less: 95,200 Btu/h for 20,000 gallons. None of these models reach that at this air temperature; use two or a gas heater.

Needed
95k Btu/h+10°F in 17.5 h
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Estimate for planning only, not professional advice. Check the manufacturer’s instructions, your local code and a licensed professional before you buy, build or install. Use at your own risk. Terms.

output = 20,000 gal × 8.33 × 10°F ÷ 17.5 h = 95,200 Btu/h

Heat pumps at this air temperature

Makers' AHRI 1160 ratings
    17 more that don't work
    • Raypak Crosswind V 455056,000 Btu/h at 50°F air
      29.8 h for +10°F
    • Raypak Crosswind V 555065,000 Btu/h at 50°F air
      25.6 h for +10°F
    • Pentair UltraTemp 11070,000 Btu/h at 50°F air
      23.8 h for +10°F
    • Raypak Crosswind V 6550 heat/cool72,000 Btu/h at 50°F air
      23.1 h for +10°F
    • Hayward HeatPro HP21105T75,000 Btu/h at 50°F air
      22.2 h for +10°F
    • Hayward HeatPro HP31105T75,000 Btu/h at 50°F air
      22.2 h for +10°F
    • Raypak Crosswind V 655075,000 Btu/h at 50°F air
      22.2 h for +10°F
    • Hayward HeatPro HP21205T75,000 Btu/h at 50°F air
      22.2 h for +10°F
    • Hayward HeatPro HP31205T75,000 Btu/h at 50°F air
      22.2 h for +10°F
    • Pentair UltraTemp 120 H/C80,000 Btu/h at 50°F air
      20.8 h for +10°F
    • Pentair UltraTemp 120Q80,000 Btu/h at 50°F air
      20.8 h for +10°F
    • Hayward HeatPro HP31405T82,000 Btu/h at 50°F air
      20.3 h for +10°F
    • Hayward HeatPro HP21405T82,000 Btu/h at 50°F air
      20.3 h for +10°F
    • Raypak Crosswind V 8550 heat/cool85,000 Btu/h at 50°F air
      19.6 h for +10°F
    • Pentair UltraTemp 140 H/C85,000 Btu/h at 50°F air
      19.6 h for +10°F
    • Raypak Crosswind V 855087,000 Btu/h at 50°F air
      19.1 h for +10°F
    • Pentair UltraTemp 14090,000 Btu/h at 50°F air
      18.5 h for +10°F
    Use a cover

    EPA: a solid cover can cut evaporation by more than 90% and save 50 to 70% of the cost of heating a pool. Whatever heater you pick, it pays first.

    Cold air

    Heat pumps put out about a third less at 50°F air than at 80°F (the makers' AHRI 1160 ratings). If you swim in spring and fall, size on the 50°F column.

    How we work it out

    heat pump output = gallons × 8.33 × 10°F ÷ 17.5 hours

    Heat pumps. California's energy code (Reference Appendix JA16.3) sizes a pool heat pump to raise the water 10°F in 17.5 hours or less. We compare that with Pentair's, Hayward's and Raypak's own ratings at the AHRI 1160 test conditions: output falls by about a third between 80°F and 50°F air.

    Gas. Hayward sizes its H-Series by pool surface area (a 30°F rise, 3½ mph wind, up to 2,000 ft), counting a third of the area for indoor pools. Heat-up time is Pentair's formula, gallons × 8.34 × rise ÷ (input × efficiency), at the 82% federal minimum efficiency.

    Solar. California requires collectors covering at least 60% of a single-family pool's surface. And whatever you pick, EPA says a solid cover saves 50 to 70% of heating costs.

    Where the numbers come from

    Guides

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