Above Ground Pool Heater: Which Type and What Size
To warm a 5,000-gallon above-ground pool by 15 °F in 24 hours, a heater needs at least about 33,000 BTU/h (British thermal units per hour) of input at 80% efficiency, or about 26,000 BTU/h delivered to the water. That minimum assumes no heat loss, so pick a bigger heater. Also use a cover, which matters as much as the heater type.
On this page (10 sections)
Above-ground pools can use the same heater types as inground pools: electric, heat pump, gas, and solar. What differs is the size of the pool, the pump that feeds the heater, and how much you want to spend on a pool that may come down each fall.
Calculator: minimum heater size for your gallons
Enter your pool's gallons, how many degrees you want to raise it, how many hours you will allow, and the heater's efficiency. Heat needed = gallons × 8.34 × degrees of rise. Divide that by the hours, then by the efficiency, to get the heater input.
With the example values (5,000 gallons, +15 °F, 24 hours, 80%), the minimum is about 33,000 BTU/h of input, or 26,000 BTU/h into the water. Real heaters must be bigger, because the pool keeps losing heat to evaporation, wind, and cool nights while it warms. For a larger pool, such as 15,000 gallons, enter your own gallons. Don't know your gallons? See the above-ground pool gallons chart. For the inground version and more detail, see the pool heater size calculator.
Heater types for above-ground pools
- Electric resistance heaters turn electricity straight into heat. They are compact and simple, but heat slowly unless they are large.
- Heat pumps move heat from the air into the water. They cost more to buy but use much less electricity for the same heat.
- Gas heaters (natural gas or propane) heat fastest and work in any weather.
- Solar options, from small mats to roof panels, use free heat from the sun but depend on the weather.
Whichever you choose, it must work with your pump's flow. Small kit pumps may not push enough water for a large heater, so check the heater's minimum and maximum flow against your pump. The Intex pool pump guide lists kit pump flows.
Electric resistance heaters
An electric resistance heater turns each kWh into about 3,412 BTU of heat (EIA). To compare one with the calculator's answer, multiply the heater's kW by 3,412 to get BTU/h. A heater much smaller than the calculator's minimum will still warm the pool, but it will take longer than the hours you entered and may not keep up on cool nights.
Intex and Bestway electric heaters for small kit pools are sold by retailers outside the US and are built for 220–240-volt power. We could not confirm a current US model on either maker's own site, so we don't list specs. If you see one for sale, check the voltage, the pool size it is rated for, and the pump flow range it needs.
Heat pumps
The U.S. Department of Energy (DOE) says heat pumps work efficiently while the outside air stays above about 45–50 °F, and their efficiency (coefficient of performance, COP) usually ranges from 3.0 to 7.0. A COP of 5 means 5 units of heat for each unit of electricity, so a heat pump uses far less power than an electric resistance heater for the same heat.
The DOE lists standard heat pump sizes of 75,000, 100,000, and 125,000 BTU. Even the smallest is more than the minimum for the example pool, which shortens heat-up time. Heat pumps also need a proper electrical circuit. Compare running costs with the heat pump vs gas heater calculator.
Gas heaters
The DOE says gas pool heaters range from 75,000 to 450,000 BTU of output, heat pools quickly, and can hold any temperature regardless of the weather. That suits pools that are used only occasionally. For a small above-ground pool, even a small gas heater is far above the minimum, so heat-ups are fast. Gas lines and venting add installation cost, and for a pool that comes down each fall, that cost may not be worth it.
Solar mats, panels, and covers
- Solar mats. Intex's 47 × 47 in solar mat (28685E) is designed to raise pool water about 5–9 °F depending on the weather. Intex lists it for above-ground pools up to 8,000 gallons and pumps under 2,000 gallons per hour.
- Solar panels. Larger collector systems work like inground solar heaters. An older version of the DOE's page put the cost to buy and install a solar pool heating system at $2,500 to $4,000.
- Solar covers. A cover is the cheapest heat saver. The DOE says covering a pool when it is not in use can save 50% to 70% of heating costs. Estimate yours with the solar pool cover savings calculator.
Running cost
Heat-up cost depends on your rates. The pool heater cost calculator works it out for gas, heat pump, and electric resistance, with your gallons and your gas or electricity price. Keeping the water warm usually costs more than the first heat-up, mostly because of evaporation, which a cover cuts.
Safety: wiring and gas lines
Safety. Heaters combine water with electricity or gas. The U.S. Consumer Product Safety Commission (CPSC) recommends ground-fault protection (GFCI) on pool equipment, including heaters near the pool on 240-volt circuits, and an electrician qualified in pool and spa work. Hire a licensed electrician for wiring and a licensed gas technician for gas lines and venting, with permits where your local code requires them. Never run a heater or pump from an extension cord near the pool unless its manual allows it.
FAQ
Do electric heaters work on above ground pools?
Yes, but small ones heat slowly. Multiply the heater's kW by 3,412 to get its BTU/h and compare it with the calculator's minimum for your pool. A heat pump gives several times more heat for the same electricity.
Can you use a heat pump on an above ground pool?
Yes, if your pump moves enough water for it and you have the right electrical circuit. The DOE says heat pumps work efficiently while the air stays above about 45–50 °F, so they suit warm-season use.
How long does it take to heat an above ground pool?
Hours = (gallons × 8.34 × degrees of rise) ÷ the BTU per hour the heater delivers. Warming 5,000 gallons by 15 °F in 24 hours takes about 26,000 BTU/h delivered to the water, before any heat loss. Covers shorten it.
Is a solar cover enough to heat an above ground pool?
A cover mostly keeps heat in rather than adding much. The DOE says a transparent bubble cover reduces the sun's heating by only 5–15% while blocking evaporation, the biggest heat loss. For a real temperature rise, add a heater or solar mats.
Sources
- U.S. DOE Energy Saver, Heat pump swimming pool heaters (45–50 °F, COP 3–7, standard sizes; archived copy, June 2026): energy.gov via web.archive.org
- U.S. DOE Energy Saver, Gas pool heaters (75,000–450,000 BTU, fast, any weather; archived copy, January 2026): energy.gov via web.archive.org
- U.S. DOE Energy Saver, Solar swimming pool heaters ($2,500–$4,000 installed; archived copy, June 2025): energy.gov via web.archive.org
- U.S. DOE Energy Saver, Swimming pool covers (50–70% heating savings, 5–15% solar gain cut; archived copy, May 2026): energy.gov via web.archive.org
- Intex, 47 in × 47 in solar mat 28685E (5–9 °F, up to 8,000 gallons, pumps under 2,000 gal/h): intexcorp.com
- U.S. EIA, British thermal units (1 kWh = 3,412 BTU): eia.gov
- U.S. CPSC, Don't swim with shocks (GFCI, 240-volt heaters, qualified electrician): cpsc.gov