A Florida pool is warm for most of the year without any help. The question is what to do about the 4–6 months when it isn't, and how to pay for that decision over the next decade. There are three mainstream heater types on the market, each with a clear use case. Pick wrong and you'll either be cold six months a year or watch the gas meter spin harder than the pool pump.
The three heater types, in plain English
| Type | How it heats | Speed | Operating cost |
|---|---|---|---|
| Gas (natural or propane) | Burns fuel under a heat exchanger. | Fast — raises a 15,000-gal pool ~1°F per hour at 400k BTU. | High per hour. Best for short, intense use. |
| Heat pump (electric) | Moves heat from the outside air into the water, like an AC run in reverse. | Slow — needs 24–72 hours to bring a cold pool up 10°F. | Low per hour. Typically 3–8x more efficient than electric resistance. |
| Solar | Pumps pool water through black panels in direct sun. | Weather-dependent. Gains 5–10°F on a good day. | Essentially free after install. No fuel, minor pump energy. |
How to pick, Florida edition
- Heat pump is the default answerfor most Florida residential pools. Our mild winters keep ambient air above ~55°F on most days — the temperature floor below which a heat pump's efficiency tanks. You trade a slower heat-up for the lowest running cost in the state.
- Gas makes sense when you use the pool rarely but want it hot fast— weekend homes, vacation rentals, or when a cold snap hits a heat pump harder than the owner wants to wait out.
- Solar is a great supplement, rarely a standalone answer. Pair solar with a heat pump to extend the season for pennies and only run the heat pump on cloudy days.
- Electric resistance heaters (other than small spa-only units) are a Florida anti-pattern. Slow, expensive, and outclassed by heat pumps in every way that matters.
Sizing — the math that protects your budget
Under-sizing a heater is the single most common mistake on Florida pool builds. The rule of thumb pool builders use:
- BTU = Gallons × 8.33 lb/gal × desired °F rise— the one-time energy to raise the pool to temperature.
- Divide BTU by the heater's output and by the hours you're willing to wait to get heat-up time.
- Add 4% for every 1,000 ft above sea level. Irrelevant in most of Florida; matters in Orlando's higher elevations barely.
For a 20,000-gallon pool rising 10°F: 20,000 × 8.33 × 10 = 1,666,000 BTU of total energy needed. A 400,000 BTU/hr gas heater delivers that in about 4 hours. A 140k BTU/hr heat pump does it in about 12 hours.
The COP conversation (for heat pumps)
Coefficient of Performance (COP) is the ratio of heat output to electrical energy consumed. An electric resistance heater has a COP of 1 — one unit of electricity delivers one unit of heat. A modern heat pump typically has a COP of 5–7, which means for the same electricity bill you get 5–7 times the heat. Colder air lowers COP; scroll-compressor units keep performance higher at cold ambient than older reciprocating designs.
Bottom line for most Florida homeowners: size a heat pump for your pool, consider adding solar if your roof works, and only go gas if you genuinely need to heat a cold pool on short notice a few times a year.