How Much Does It Cost to Heat a Pool?
Last updated 15 October 2026
How much does it cost to heat a pool? Cost depends on the heat needed and the energy price. Pool gallons alone cannot give a monthly bill. Keep warming the water apart from replacing heat lost while holding it warm.
Find water-only heat from gallons and the wanted temperature rise. Add stated losses for the time you plan to heat. Use the heater's efficiency or COP to turn useful heat into fuel or power. Then apply tariffs. A zero-loss result is a lower bound. It cannot predict a season's bill. Note cover use and weather. Unknown losses stay unknown.
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Cost to heat a pool: two different loads
Initial heat-up changes the water temperature. Maintenance replaces heat that escapes while the pool is held warm. A pool that has already reached its target can still consume energy as heat leaves it. Conversely, a short one-time warm-up should not automatically include a whole season of maintenance.
The heater calculator uses US gallons × 8.33 × °F rise for water-only Btu. The Sta-Rite engineering manual, printed page 27 supplies the heat convention. Multiply a stated loss in Btu/h by the hours it applies. Do not count heat-up hours again as maintenance hours.
Pool heat cost and surface area
Volume affects water-only warming energy. Exposed surface area is relevant to heat-loss methods. A small surface with greater average depth can hold the same gallons as a larger shallow pool, yet its exposed area differs.
Cover state and wind affect heat loss. So does the water-air temperature difference. Record those conditions as context. They are not secret multipliers in this tool. If loss is unknown, show the water-only lower bound and leave maintenance expense unresolved.
The historical outdoor table used in the heater tool is a named scenario at 3.5 mph wind. It is not a local forecast. A cover cannot be accounted for by applying an arbitrary universal reduction to that table.
Efficiency and COP convert the same useful heat
Divide useful heat by thermal efficiency to get gas input energy. Resistance uses the same form. For a heat pump, divide by COP. Keep the energy units the same. Read both COP and output at conditions that match the task.
The Raypak catalogue separates input from useful output. It has heat-pump tables for stated conditions. It does not give one COP for every month. See the three-type comparison before comparing unlike labels.
A transparent lower-bound scenario
An artificial 15,000-US-gallon pool warmed by 10°F needs 1,249,500 Btu before losses. That is about 366.19 kWh of useful heat. At COP 5, purchased electricity is about 73.24 kWh. At an illustrative 0.20 currency/kWh, that is about 14.65 currency units for the event.
At gas efficiency 0.80, the same water-only event needs 15.61875 therms. Its expense waits for a rate or uses the clearly labelled reference-rate scenario. Neither calculation includes unknown outdoor losses, purchase price, installation or standing charges.
Dated national rates versus your tariff
EIA reports a US residential average of 18.31 cents/kWh for July 2026. BLS's US city electricity series reports 19.6 cents/kWh for September 2026. The calculator uses those as editable reference endpoints, not a statistical confidence interval or a local quote.
For gas, BLS's September series reports 1.700 USD/therm. EIA's July residential series reports 26.45 USD per thousand cubic feet. Using EIA's stated 10.37 therms per thousand cubic feet gives about 2.55 USD/therm as a second reference. These all-in national averages can differ from marginal local charges.
FAQ
Can I multiply one warm-up by every swimming day?
Only if that is the actual repeated task. A pool that remains warm may need maintenance rather than a full repeated temperature rise. A pool allowed to cool needs its real next starting temperature. Keep event counts and maintenance hours separate to avoid double counting heat.
Does a lower water target reduce the bill by a fixed amount?
The water-only warm-up calculation uses the actual temperature rise. Ongoing losses also depend on conditions and the chosen model. This page does not assign a universal percentage saving per degree. Compare two explicitly stated scenarios with the same source and operating-period assumptions.
Verdict on cost to heat a pool
Price the task to heat a pool with a stated event and loss scenario. Use the heating-cost calculator to save the maths and rate sources. Version 1.0 uses the named heat and rate references. Unknown losses remain outside the lower bound.