Pool Heater Finder: heat pump, gas, or solar — and what size?
Two questions decide a pool heater — which type (heat pump, gas, or solar) and what size — and most buying guides answer neither for your pool. Tell us your gallons, whether it's above- or in-ground, your region and swim season, and what matters most, and this hands you the type, the BTU to look for, the catch nobody mentions, and the showdown that ranks your actual options.
Find your pool heater
Tell us about your pool and what matters most. We'll name the right heater type, the size to look for, the honest catch, and the showdown that ranks your options — not a 20-screen article to wade through. Updates live.
Don't know your gallons? Work it out here →
Exact geometry at 7.48 gal/ft³. Kidney shapes, diving hoppers, litres and salt/turnover figures live in the full Pool Volume Calculator.
👆 Set your pool and pick what matters to get your heater.
Don't know your gallons? Estimate from your pool's size
Rough estimate (rectangle ×7.5, oval ×6.7, round ×5.9 gal per sq-ft-ft; enter the diameter for a round pool). Need the exact number? The full pool volume calculator handles every shape and depth profile.
Sizing and picks come from the same research as our pool-heaters showdown — a starting point, not a permit. A heat pump can't heat below ~50°F; solar only works while the sun's out; gas costs the most to run. Have a pro confirm the final BTU. Pool heaters generally don't earn a federal tax credit.
Which heater type wins (by climate and goal)
The type decision in one grid — same logic as the tool above. A heat pump is the warm-climate default; gas is the answer for speed, cold weather, and spas; solar is the cheapest to run when you have sun and patience.
| What matters most | Warm (FL / Sun Belt) | Moderate | Cold |
|---|---|---|---|
| Lowest running cost | Heat pump | Heat pump | Gas |
| Fast heat / any weather / a spa | Gas | Gas | Gas |
| Extend my swim season | Heat pump | Heat pump | Gas |
| Lowest bills, and I’m patient | Solar | Solar | Solar |
What size heater for your pool
Starting-point sizing, straight from our heaters showdown. Heat pumps are sized to hold a temperature; gas heaters are sized to raise it fast — which is why the BTU numbers differ so much for the same pool. A screened pool or a windy, exposed one leans toward the next tier up. Have a pro confirm the final number.
| Pool volume | Heat pump | Gas heater |
|---|---|---|
| ~5,000 gal | 55,000–70,000 BTU | 200,000–250,000 BTU |
| ~10,000 gal | 55,000–70,000 BTU | 200,000–250,000 BTU |
| ~15,000 gal | 80,000–100,000 BTU | 200,000–250,000 BTU |
| ~20,000 gal | 110,000–130,000 BTU | 250,000–400,000 BTU |
| ~25,000 gal | 140,000–160,000 BTU | 250,000–400,000 BTU |
| ~35,000 gal | 180,000+ BTU | 400,000 BTU |
Solar is sized by panel area, not BTU: aim for panel area equal to about 50–100% of your pool's surface, toward the high end in a cooler climate — and about a third more again under a screen enclosure (Florida Solar Energy Center sizing).
How the finder decides
Type follows your goal, then your climate. Want fast heat, any-weather reliability, or a spa? That's gas — the only type that heats on demand in a cold snap. Want the lowest bills and you're patient? That's solar, when the sun cooperates. Otherwise — lowest running cost or a longer season — it's a heat pump in a warm or moderate climate, and gas in a cold one (because a heat pump can't heat below ~50°F, full stop).
Size follows your gallons. A heat pump runs long to hold a temperature, so it's rated lower for the same pool; a gas heater is sized to raise the water fast, so its BTU number is much higher. Both scale with volume, and both get bumped up a tier for a screened or exposed pool that loses more heat.
The honest limits stay on the page. A heat pump quits below ~50°F. Solar does nothing at night or under cloud. Gas costs the most to run. And pool heaters generally earn no federal tax credit — solar-pool heating is specifically excluded from the Residential Clean Energy Credit, and the 25C heat-pump credit expired at the end of 2025. We'd rather tell you than let a rosy calculator do the selling.
Then pick your model
Heat pump vs gas vs solar — the full showdown → ·Best in-ground heat pumps (by pool size) → ·Best budget heat pumps (small above-ground) → ·Best mid-size heat pumps (above-ground) → ·Coolers & reversible heat/cool →
FAQ
What size pool heater do I need?
Size to your pool's volume, not "bigger is better." As a rough gas-heater guide: a pool up to ~15,000 gallons wants about 200,000–250,000 BTU, 15,000–25,000 gallons wants 250,000–400,000 BTU, and a large or windy, exposed pool wants 400,000 BTU. Heat pumps are rated in BTU too but sized to hold a temperature rather than blast heat — a ~140,000-BTU unit suits most average in-ground pools, and a 55,000-BTU unit covers a pool up to ~10,000 gallons. An undersized heater never quite gets there; an oversized one wastes money — have a pro confirm the number for your pool.
Heat pump vs gas vs solar — which is best?
They win on different things. A heat pump is far cheaper to run and is the default in warm climates, but it warms gradually and loses efficiency once the air drops below about 50°F. Gas heats fastest and works in any weather — the only type that beats a cold snap or runs a spa — but it costs the most to run. Solar has essentially no running cost, but it only adds heat while the sun is out. Pick the heat pump for low cost in mild weather, gas for speed and cold, and solar for the lowest bills if you get reliable sun and you're patient.
At what temperature does a pool heat pump stop working?
A pool heat pump pulls warmth out of the surrounding air, so its efficiency falls as the air cools and it effectively stops being practical below about 50°F. That's why heat pumps are the default in Florida and the Sun Belt, and why cold-climate owners who want to swim in the shoulder months reach for a gas heater instead.
Does a screened (caged) pool change which heater I need?
Yes. Florida Solar Energy Center testing measured a standard screen enclosure blocking 30–40% of the solar energy reaching the pool on a clear day, so a caged pool runs noticeably cooler through fall and spring and leans on the heater more than an open one. Heat pumps and gas heaters work the same under a cage — they just have a bigger gap to close. If you go solar, plan for about a third more panel area than an identical unscreened pool.
Do pool heaters qualify for a tax credit?
Usually not. Pool heaters generally don't qualify for federal energy tax credits, and solar pool heating is specifically excluded from the federal Residential Clean Energy Credit (that solar credit is for heating your home, not your pool). The federal 25C heat-pump credit also expired at the end of 2025. Some local utilities offer their own rebates on efficient pool equipment, so it's worth checking yours — but don't count on a federal write-off.