Pool Heat Pump Sizing Calculator
Find the BTU size of pool heat pump you need to hold your target water temperature.
How to size a pool heat pump
A pool heat pump (also called a pool heat pump heater) is sized to overcome heat loss from the swimming pool's water surface. The common rule of thumb:
BTU/hr ≈ surface area (sq ft) × temperature rise (°F) × loss factor (12 uncovered, 8 covered)
So a 32×16 ft pool (512 sq ft) raising water 14°F needs about 86,000 BTU/hr uncovered — and far less with a cover.
What affects the size you need
- Surface area — most heat is lost from the surface, so a larger pool needs more BTU.
- Target vs air temperature — bigger rise = bigger unit.
- Cover — a solar/pool cover cuts heat loss (and running cost) by roughly a third.
- Wind & location — exposed, windy sites lose heat faster.
Running cost
Pool heat pumps are efficient (COP 4–6) but pools are big, so monthly cost varies widely with climate and how long the season runs. A cover, wind breaks, and heating only when in use keep bills down.
Frequently asked questions
What size pool heat pump do I need?
About surface area × temperature rise × 12 (uncovered) BTU/hr. A 32×16 ft pool raising 14°F needs ~86,000 BTU/hr uncovered — much less with a cover.
How long does a pool heat pump take to heat a pool?
Typically 24–72 hours for the initial heat-up depending on pool size, temperature rise and unit capacity; a cover dramatically speeds it up and maintains temperature.
Is a pool heat pump cheaper than gas?
To run, usually yes — pool heat pumps are very efficient (COP 4–6). Gas heaters heat faster but cost much more per hour to operate.
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⚠️ Rule-of-thumb estimate, not a substitute for a professional Manual J load calculation. Based on US DOE / ENERGY STAR guidance.