Pool Heating Cost Calculator
Estimate monthly heating costs for gas, electric, heat pump, and solar heaters.
Safety
Cost estimates are approximate. Actual costs depend on weather, pool cover use, thermostat settings, wind exposure, and heater efficiency. A pool cover reduces heating costs by 50–70%.
An hour of 100,000 BTU heating costs about $0.88 with a heat pump, $1.83 with gas and $4.40 with electric resistance at $0.15/kWh and $1.50/therm. The heater type sets the rate, but a cover sets the hours — it cuts pool heating costs by 50–70%, more than any change of equipment. Enter your pool and fuel price above for your own figure.
What Actually Drives a Pool's Heating Bill
Heating a pool costs whatever it costs to replace the heat the water keeps losing. Two things set that bill: how fast heat escapes the surface, and how efficiently your heater turns fuel into heat in the water. The first is why a cover is the highest-return purchase in pool heating — most of a pool's heat loss is evaporation off the top, and a cover cuts heating costs by roughly 50 to 70%. No change of heater comes close to that return. The second is the choice between gas, a heat pump, and electric resistance, and the gap between them is enormous.
Efficiency Is Not a Rounding Error Here
A gas heater burns about a therm (100,000 BTU of fuel) to deliver 82,000 BTU into the water — roughly 82% efficient — and it does it regardless of the weather, which is its real advantage. An electric resistance heater is nearly 100% efficient at converting electricity to heat, but electricity is an expensive way to buy raw BTU, so it is the most costly to run by a wide margin. A heat pump does not make heat at all — it moves heat out of the air into the water — so it delivers around five units of heat for every unit of electricity (a coefficient of performance, COP, near 5). That is why the same BTU of warming costs so little through a heat pump.
Cost to Deliver the Same Heat
One hour of a 100,000 BTU heater of each type, at representative fuel prices. The energy figures come straight from the calculator's own rules.
| Heater type | Energy / hr | Price | Cost / hr |
|---|---|---|---|
| Heat pump (COP 5) | 5.9 kWh | $0.15/kWh | $0.88 |
| Gas heater | 1.2 therm | $1.50/therm | $1.83 |
| Electric resistance | 29.3 kWh | $0.15/kWh | $4.40 |
Prices vary by region and season — enter your own above. The ranking rarely changes: a heat pump runs at a fraction of gas, and electric resistance is several times more expensive than either.
The Gas-vs-Heat-Pump Crossover
On operating cost a heat pump wins almost every time — it runs at three to five times less than gas to hold a temperature. The catch is that it pulls heat from the surrounding air, so its efficiency falls as the air cools and drops off sharply below about 50°F. It also heats slowly. Gas does the opposite: it costs more per hour but heats fast and does not care how cold the air is.
So the crossover is about how you use the pool, not just the price of fuel. If you keep the pool at a steady temperature all season in a mild climate, a heat pump is far cheaper to live with. If you heat on demand — a cold weekend, an early-spring party, a spa you want hot in an hour — gas earns its higher running cost by getting there quickly. Many owners in cold climates end up with both. Size the unit first with the pool heater size calculator, and read cost to run a pool heat pump for the heat-pump case in full.
Cutting the Bill Without Changing the Heater
Before spending on a new heater, spend on the losses. A cover — solid or liquid — is the biggest single lever, cutting evaporation and the heat that leaves with it. Dropping the set temperature a couple of degrees, running the heater on a schedule instead of around the clock, and using a windbreak on an exposed pool all compound with it. Fold the heating number into your full running cost with the pool maintenance cost calculator or the cost of ownership calculator, and see how to cut pool maintenance cost for the rest.