Heat Pump vs Gas Pool Heater — Season Cost Compared
Compare heat pump, natural gas and propane on the same pool and season: identical energy demand, your fuel prices, with the cold-air and heat-up caveats spelled out.
Quick answer
Same pool, same season, same energy demand — the fuel decides the bill. A heat pump delivering heat at COP 5 turns each kWh of electricity into ≈ 17,060 BTU of pool heat, so at $0.17/kWh each million BTU costs about $10. An 82% efficient gas heater pays ≈ $22 per million BTU at $1.80/therm, and propane more. That's the whole economic argument in one line — the comparison calculator below runs it on your pool, your season and your rates.
Industry / community reference · 2026-10-31
What the comparison can't see (and you must)
Air temperature breaks the heat pump's math in cold weather. A heat pump doesn't make heat, it harvests it from air, and harvests less as the air cools. Manufacturers rate COP 5–6 at 80°F air; the IECC low-air floor is COP 4.0; below ~55°F ambient, output and efficiency keep sliding. A calculator held at COP 5 is honest about warm-season swimming and increasingly optimistic the further north — or the further into fall — you swim.
Independent second source · 2026-10-31Gas pays for speed, not efficiency. A gas heater doesn't care what the air is doing — it burns fuel and delivers ≥82% of it to the water by federal floor (10 CFR 430.32), which is why gas owns the "heat it by Saturday" job and cold-climate pools. If your gas line is undersized, though, the biggest gas heater is a paper spec until a plumber upgrades the run.
Official regulation text (eCFR) · 2026-10-31Equipment price is the third column. Roughly: gas heaters cost less at purchase, heat pumps more — the fuel savings must repay the difference over seasons. In a warm climate with 150+ swim days the payback is real; in a cold climate with 40 swim days it usually never lands. Propane owners have a third option worth pricing: a heat pump for the shoulder season and a small gas unit for cold snaps.
How to read the result
The three bars are the same energy demand priced three ways — that's the only fair comparison, and it's why the calculator asks for your pool and season rather than taking a heater as given. Adjust the fuel prices to your bills and the ranking updates instantly. If the heat pump's bar looks too good to be true for your climate, lower the COP assumption mentally for cold months — or lean on the running cost calculator to test specific COP values at your kWh price.
From here
New to sizing? Start with the BTU calculator to know what capacity you're shopping for, and the sizing guide for the physics behind the margins.
FAQ
Is a heat pump or gas pool heater better?
For keeping a pool warm through a long, mild season, the heat pump usually wins on running cost — it moves roughly 5 units of heat per unit of electricity. Gas wins when you need fast heat-ups, heat in cold air, or only swim occasionally; propane behaves like gas at a higher fuel price. The calculator above prices all three on your pool.
How much cheaper is a heat pump to run?
At typical U.S. rates ($0.17/kWh, $1.80/therm), delivering one million BTU costs roughly $10 through a heat pump at COP 5 versus about $22 through an 82% efficient gas heater and more through propane. Cold air cuts the heat pump's advantage because COP falls as temperature drops.
Can a heat pump heat a pool quickly?
Not as fast as gas for the same rated BTU, and slower still in cold air. Heat-pump sizing convention leaves margin for cold-air derating; for 'heat it this weekend' use cases — vacation homes, occasional swims — a gas heater or a hybrid heat-pump-plus-small-gas setup is the usual answer.
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