Swimming Pool Heating Cost Calculator
Find out exactly what it costs to heat your pool — gas, electric, or heat pump.
Calculate Your Pool Heating Cost
Heater size: 100,000 BTU/hr — DOE formula (392 sq ft x 20°F rise x 12), rounded to the nearest standard residential size.
Pool Heater Monthly Cost Comparison
| Heater Type | Small — 288 sq ft (75k BTU) | Medium — 392 sq ft (100k BTU) | Large — 512 sq ft (125k BTU) |
|---|---|---|---|
| Gas Heater | ~$316/mo | ~$421/mo | ~$527/mo |
| Electric Resistance | ~$973/mo | ~$1,297/mo | ~$1,621/mo |
| Heat Pump | ~$195/mo | ~$259/mo | ~$324/mo |
Heater outputs are DOE’s three standard residential sizes, which is what its sizing formula (pool area x temperature rise x 12) gives for a 288 / 392 / 512 sq ft pool at a 20°F rise. Columns are surface area, not volume — a pool loses its heat at the water surface, so depth barely changes the running cost. Run at full output 8 hrs/day for 30 days. Natural gas $1.44/therm (EIA, winter average, November 2025 - March 2026 (US); December 2025 - February 2026 (by state)) at 82% thermal efficiency; electricity 18.44¢/kWh (EIA Electric Power Monthly, Table 5.6.A, May 2026); heat pump COP 5.0, within DOE’s 3.0–7.0 range and valid only above about 45–50°F outside air.
The electric resistance row is a reference cost, not a shopping list: at these outputs it means a 22 to 37 kW load, and resistance pool heaters are only made in small sizes — commonly 11–15 kW — for spas and very small pools. A pool cover moves these numbers further than the heater choice does; DOE’s own operating-cost table for a 1,000 sq ft pool spans $49 to $1,989 a year for the same heat pump, depending on location and whether a cover is used.
Which Pool Heater Is Cheapest to Run?
A heat pump pool heater is the cheapest to run, but by different margins depending on what you compare it with. At current US average rates it costs about 40% less than a gas heater and about five times less than electric resistance for the same heat delivered. DOE puts pool heat pump COPs at 3.0–7.0, and they hold that only while the outside air stays above about 45–50°F — which is most of the southern and coastal US swimming season, and not much of a northern shoulder season.
Gas heaters heat a pool fastest and work at any air temperature, which is why they dominate in northern states and for pools used occasionally rather than continuously. Electric resistance is the outlier: it has the lowest purchase price but by far the highest running cost, and it is only made in small sizes — commonly 11–15 kW, enough for a spa or a very small pool. A resistance heater matching a 125,000 BTU/hr pool heat pump would draw about 37 kW, which no ordinary residential service supports.
Size the heater on surface area, not gallons. DOE’s formula is pool area in square feet x the temperature rise you need x 12, which gives BTU/hr. A 16 x 32 ft pool needing a 20°F rise works out at about 123,000 BTU/hr — near the top of DOE’s standard residential range of 75,000, 100,000 and 125,000 BTU. This matters for running cost too: a pool loses nearly all its heat by evaporation from the water surface, so doubling the depth barely changes the monthly bill, while doubling the surface area roughly doubles it. For the same reason a cover is the single change that moves the number most — DOE’s own operating-cost table for a 1,000 sq ft pool spans $49 to $1,989 a year for the same heat pump, depending on location and cover use.
The same efficiency principles apply to home heating. Our heat pump running cost calculator shows the monthly savings versus gas or electric resistance for your whole home. Use our free heating cost calculator to estimate your annual spend across all heating types.