What is the difference between a gas and heat pump pool heater?
The difference is where the heat comes from. A gas heater makes its own heat: it burns natural gas or propane in a combustion chamber and passes your pool water over a hot copper heat exchanger. A heat pump makes no heat at all. It runs a refrigeration cycle in reverse, pulling warmth out of the surrounding air with a fan and compressor and dumping that warmth into the water. That single design difference drives every tradeoff below.
Because a gas heater generates heat directly, its output does not care what the weather is doing. Fire it up on a 40 degree morning and it still pours out the same 3 to 5 degrees F per hour. A heat pump depends on there being usable warmth in the air to harvest, so its output rises and falls with the air temperature and it works best on a warm day.
The payoff for the heat pump's slower, weather-dependent approach is efficiency. A gas heater is a fuel burner, so at best it turns 80 to 95% of the gas you pay for into heat. A heat pump only pays to move heat, not create it, so it returns a COP of 4 to 6: four to six units of heat for every unit of electricity. That is why the two heaters can cost so differently to run. If you are still sizing a unit, our pool heater calculator estimates the BTU output your pool needs, and the best pool heater guide covers specific models.
Which is cheaper to run, gas or a heat pump?
A heat pump is far cheaper to run, usually by two to four times. Because it moves heat instead of burning fuel, a typical residential heat pump costs around $50 to $150 a month to keep a pool warm through the season, while a gas heater in similar use runs $200 to $500 a month or more. Propane pushes the gas figure higher still, since propane costs more per unit of heat than natural gas. Over a full swim season that gap is often the whole price difference between the two units.
The catch is climate and rates. A heat pump's savings depend on mild air and reasonable electricity prices, so in a cool climate or an expensive utility market the advantage shrinks. Gas closes the gap when you heat rarely and fast: firing a gas heater for a few hours before a weekend swim and shutting it off can cost less than running a heat pump around the clock to hold temperature. How you heat matters as much as which heater you own.
Whatever you run, the cheapest heat is the heat you keep. A solar cover cuts evaporation, which is where most pool heat escapes, and it can slash a heating bill by half or more. Pair either heater with a cover, and see our best solar pool cover picks. Right-sizing the unit to your water volume with the pool volume calculator also keeps you from paying to run an oversized heater.
Which heats a pool faster, and does a heat pump work in cold weather?
Gas heats far faster, and it is the only one that reliably works in the cold. A gas heater brings water up roughly 3 to 5 degrees F per hour regardless of the weather, so it can warm a cool pool in a single afternoon and reheat a spa in under an hour. A heat pump manages only about 1 to 2 degrees F per hour in good conditions, so bringing a cold pool up to temperature from scratch can take 24 to 72 hours. Once the water is warm, though, a heat pump holds it there efficiently.
Cold air is the heat pump's hard limit. Standard models need air above about 45 to 50 degrees F to work, and their output drops steadily as the air cools because there is less warmth to harvest. Below that range many units cut out entirely. Inverter and cold-climate heat pumps stretch that window lower, but none match a gas heater's ability to shrug off freezing mornings. A heat pump is a season-extender for spring and fall, not a dead-of-winter heater.
This is where gas earns its keep. If you want to swim on demand in early spring, run a spa that needs to be hot in twenty minutes, or heat a pool in a genuinely cold climate, gas does the job when a heat pump cannot. For a pool you use predictably through a warm season, the heat pump's slower ramp is a non-issue because you set a temperature and let it hold.
Gas or heat pump: which pool heater should you buy?
Buy a heat pump for most residential pools in a warm or temperate climate. It costs a fraction as much to run, lasts about 10 to 20 years because it has no corrosive combustion, and runs cleaner and quieter. If you want to extend your season by a couple of months on each end and keep the water at a steady temperature without dreading the bill, the heat pump is the smarter long-term buy despite its higher sticker price.
Buy gas if you live somewhere cold, heat a spa, or want warmth on demand. Gas heats fast at any air temperature, so it suits pools used sporadically (heat it up, swim, shut it off), spas that need to be hot quickly, and northern climates where a heat pump cannot keep up. Its lower upfront cost and smaller footprint are a bonus if you already have a gas line at the pad.
Size whichever you choose to your pool, not to a round number. Start from your water volume with the pool volume calculator, estimate the output you need with the pool heater calculator, then buy a unit rated comfortably above that. If your climate leans mild and sunny, also price out solar before you commit, since it can carry much of the load for free. Compare specific units in our best pool heater guide.
Gas wins on
- +Heats fast at any air temperature: 3 to 5 degrees F per hour on demand.
- +The only choice for cold climates, spas, and warm-on-demand swimming.
- +Lower upfront cost and a smaller footprint at the pad.
Heat Pump wins on
- +Far cheaper to run: a COP of 4 to 6 means a fraction of the energy cost.
- +Lasts about twice as long, with no combustion to corrode the exchanger.
- +Cleaner, quieter, and ideal for holding a steady warm-season temperature.
The verdict
Buy the heat pump for a typical residential pool in a warm or temperate climate. It costs two to four times less to run, lasts about 10 to 20 years, and holds a steady temperature cleanly and quietly, which pays back its higher price over a few seasons. Choose gas instead if you live in a cold climate, heat a spa, or want the water warm on demand, because gas heats 3 to 5 degrees F per hour at any air temperature while a heat pump stalls below about 45 to 50 degrees F. Size either one to your water volume with the pool heater calculator, add a solar cover to cut the bill, and compare specific models in our best pool heater guide.
Related: Best pool heaters, Pool heater size calculator, Best solar pool heaters.
Frequently asked questions
Which is cheaper, a gas heater or a heat pump?
A heat pump is much cheaper to run, usually by two to four times. It moves heat rather than burning fuel, so a typical unit costs around $50 to $150 a month against $200 to $500 or more for gas in similar use, and propane costs even more than natural gas. Gas has the lower upfront price (about $1,500 to $3,000 versus $2,500 to $5,000+), but the heat pump's running savings usually erase that gap within a season or two. A solar cover lowers the bill on either one.
Is a heat pump better than a gas pool heater?
For most pools in a warm or temperate climate, yes. A heat pump costs a fraction as much to run, lasts about 10 to 20 years with no combustion to corrode it, and runs cleaner and quieter. Gas is the better heater only when you need warmth fast or in the cold: a heat pump heats slowly and stalls below about 45 to 50 degrees F of air temperature, so it is a season-extender, not an all-weather heater. Match the choice to your climate and how you use the pool.
How long does a heat pump take to heat a pool?
Plan on 24 to 72 hours to bring a cool pool up to swimming temperature from scratch, since a heat pump adds only about 1 to 2 degrees F per hour and slows further in cooler air. A gas heater does the same job in an afternoon at 3 to 5 degrees F per hour. The upside is that once a heat pump reaches your target, it holds that temperature efficiently, so the slow initial ramp only matters at startup. A solar cover speeds heating and cuts the loss overnight.
Can a heat pump heat a pool in winter?
Not well in a genuinely cold climate. Standard heat pumps need air above about 45 to 50 degrees F to work, and their output falls as the air cools until many shut off entirely below that range. Inverter and cold-climate models push the window lower but still cannot match gas in freezing weather. If you want to swim through a cold winter, a gas heater is the reliable choice; a heat pump shines for extending spring and fall in a mild climate.
What are the disadvantages of a heat pump pool heater?
Three things: it heats slowly (about 1 to 2 degrees F per hour, so 24 to 72 hours from cold), it needs air above roughly 45 to 50 degrees F so it struggles in cold weather, and it has a higher upfront cost than gas. It also needs a dedicated 240V circuit and enough open air around it for the fan to breathe. Those tradeoffs are worth it in a warm climate for the low running cost and long life, but they make gas the better pick for cold or on-demand heating.