Gas vs heat pump vs solar pool heater
2026-09-04 · 8 min read
Three ways to put heat in a pool, and the ranking flips depending on your utility rates, your climate and how much notice you are willing to give before you swim.
Best overall
Heat pump
Cheapest heat per BTU on grid power in mild weather, and it runs unattended.
Best budget
Solar
Effectively free heat once installed; you take the weather you are given.
Best for large pools
Gas
The only one that heats a big body of water fast, whatever the air is doing.
How they compare where it matters
Our pick — heat pump
| Factor | Gas heater | Heat pump | Solar |
|---|---|---|---|
| Speed | Fastest — hours | Slow — a day or more | Slowest, weather-bound |
| Running cost | Fuel price × BTU, no leverage | Multiplies each kWh several times over | Pump power only |
| Cold-weather output | Unaffected | Falls off below ~50 °F air | None |
| Install | Gas line and venting | Electrical capacity and airflow | Roof or ground area |
| Maintenance | Exchanger, burner, venting | Coil, fan, refrigerant circuit | Almost none |
| Best use | Occasional, on demand | Season extension | Season extension, free |
Electricity used
17.30¢/kWh — US EIA average residential, 2025.
Gas used
$24.09 per Mcf ≈ $2.32/therm — US EIA, June 2026.
The lever nobody buys
A cover. It cuts the loss all three are fighting.
Do the arithmetic with your own rates
The figures on this page use the US averages the EIA published and this site read on 2026-09-04: 17.30 cents per kilowatt-hour for residential electricity in 2025, and $24.09 per thousand cubic feet of residential natural gas in June 2026 — about $2.32 a therm. Your own tariff may put these in a completely different order, which is exactly why the heater sizing calculator prices the same heat-up on both fuels and lets you change the inputs.
Gas
Gas heaters convert fuel to heat at a fixed efficiency — high eighties per cent on a modern unit — and that is the ceiling. What you buy is speed and independence from weather: a gas heater will take a cold pool to swimming temperature overnight in November. What you pay is the fuel, every time, with no multiplier working for you.
Heat pump
A heat pump does not make heat, it moves it, which is why each kilowatt-hour of electricity delivers several kilowatt-hours of heat into the water. That multiplier is the whole argument, and it collapses as the air gets colder. In a mild climate a heat pump is comfortably the cheapest heat available; in a genuine winter it is an expensive fan.
Solar
Unglazed collectors and the existing pump. Once installed the heat is free and the maintenance is close to zero. The catch is control: you get the weather you get, and you need real collector area — a token panel array on a shaded roof is decoration. Solar pairs well with a heat pump: solar carries the shoulder season, the heat pump covers the evenings it cannot.
The upgrade that beats all three
Most of a pool’s heat leaves through the surface, overnight, by evaporation. A cover stops the majority of that for a fraction of any heater’s price, and it makes every one of these three cheaper to run — see the cover comparison before you spend money on capacity.
Buying checklist
- Price the heat-up on your own utility rates, not a national average.
- Check gas line capacity or electrical service before choosing.
- For a heat pump, check the coldest air temperature you expect to swim in.
- For solar, measure the collector area honestly against the pool surface.
- Buy a cover first, whichever heater you end up with.