Pool Heat Pumps: Sizing, Real Running Costs and Who They’re Right For (2026)
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Key takeaways
- A pool heat pump does not burn fuel. It pulls heat from the outside air and moves it into the water, delivering about 4 to 6 units of heat for every unit of electricity when the air is warm.
- Per unit of heat, that usually makes it the cheapest way to warm a pool: in our worked example, 1 million BTU costs about $10 with a heat pump, about $18 with natural gas and about $35 with propane.
- Heat pumps work best when the air stays above about 50°F. They heat slowly, so they suit pools kept warm all season, not a quick weekend warm-up.
- Most residential units cost roughly $2,500 to $5,500, and installed totals often land around $3,500 to $7,000 depending on electrical and plumbing work.
“Pool heat pump” sounds like a pool pump, but it is a different machine. Your pool pump circulates water. A heat pump sits in that circulation loop, after the filter, and warms the water as it passes through, using the same refrigeration cycle as a home heat pump or air conditioner run in reverse. It needs your pool pump running to work at all, which is one more reason a quiet, efficient variable-speed pump pairs well with one.
How a pool heat pump works
A fan draws outside air across an evaporator coil filled with refrigerant. The refrigerant absorbs heat from the air, a compressor squeezes it to raise its temperature, and a heat exchanger hands that heat to your pool water. Because the unit moves heat instead of making it, it can put out several times more heat energy than the electricity it uses. That ratio is the coefficient of performance (COP). Manufacturers rate COP at standard test conditions; a unit that shows a COP of 5 or 6 at 80°F air will be noticeably lower on a 55°F evening.
What it costs to heat a pool: heat pump vs gas vs propane
Here is the cost to put 1 million BTU of heat into a pool, using common example prices. Swap in your own rates; the ranking rarely changes.
| Heater | Assumption | Energy used | Cost per 1 million BTU |
|---|---|---|---|
| Heat pump (warm air) | COP 5, 17¢ per kWh | about 59 kWh | about $10 |
| Heat pump (cool air) | COP 4, 17¢ per kWh | about 73 kWh | about $12 |
| Natural gas heater | 85% efficient, $1.50 per therm | about 11.8 therms | about $18 |
| Propane heater | 85% efficient, $2.75 per gallon | about 12.9 gallons | about $35 |
Math: 1 million BTU = 293 kWh. A heat pump divides that by its COP. Gas uses 10 therms per million BTU, propane about 10.9 gallons, each divided by heater efficiency.
The trade-off is speed and cold-weather performance. A gas heater can raise a cold pool several degrees in hours and works in any weather. A heat pump may take a day or two to bring a cold pool up to temperature, then holds it there cheaply. Keeping a solar cover on at night cuts heat loss sharply with either type.
How to size a pool heat pump
Heat pumps are rated in BTU per hour, most commonly 50,000 to 140,000 BTU for residential pools. A widely used rule of thumb for outdoor pools:
BTU per hour = pool surface area (sq ft) x desired temperature rise (°F) x 12
Example: a 16 x 32 foot pool (512 sq ft) that you want 15°F warmer than the average air temperature: 512 x 15 x 12 = about 92,000 BTU per hour, so a unit around 100,000 BTU is a sensible pick. Go up a size if the pool is windy, shaded, has no cover, or you swim early in spring and late in fall. Undersizing is the most common mistake: a small unit will run constantly and still fall behind on cool nights.
- Surface area, not gallons, drives sizing, because most heat is lost from the surface.
- Climate matters. In mild climates (Florida, southern California, Arizona) heat pumps can extend the season by months. In northern climates they work well from late spring to early fall.
- Use a cover. A solar cover can cut the heat you need by half or more, which lets a smaller heat pump do the job.
Installation basics
- Electrical: most units need a dedicated 230-volt circuit, often 30 to 50 amps. This is the biggest installation variable, and it needs a licensed electrician.
- Plumbing: the heater goes after the filter and before any chlorinator or salt cell, so concentrated chlorine does not pass through the heat exchanger.
- Placement: it needs open airflow on all sides and clearance above for the fan, on a level pad. Do not box it in or put it under a deck.
- Flow: the pool pump has to deliver the heater’s minimum flow rate. A variable-speed pump may need its speed raised while heating.
Get an installed quote that itemizes the unit, electrical, plumbing and pad. Our quote request form connects you with a local pool pro.
Brands to know
The names you will see most in the U.S. residential market are Hayward (HeatPro), Pentair (UltraTemp), AquaCal and Raypak. Compare warranty length on the compressor and heat exchanger (titanium heat exchangers resist corrosion and are standard on better units), noise rating, minimum operating temperature, and whether the unit can also cool the pool in hot climates.
Compare pool heat pumps at Doheny’s
Above-ground pools
Smaller heat pumps (roughly 20,000 to 50,000 BTU) are made for above-ground pools and some run on 115 volts. Check that your above-ground pump delivers the heater’s minimum flow; many small cartridge pumps do not. See our above-ground pool pump guide for sizing the pump side.
When a heat pump is the wrong choice
- You want to heat a cold pool fast for occasional use, like a weekend party in April. Gas wins on speed.
- Your air temperatures are regularly below about 45 to 50°F when you want to swim.
- Your electrical panel cannot support another large 230-volt circuit without an expensive upgrade.
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FAQ
How much does a pool heat pump cost?
Most residential units cost roughly $2,500 to $5,500. Installed totals often land around $3,500 to $7,000, mainly depending on the electrical work.
How much does it cost to run a pool heat pump?
Per unit of heat, usually far less than gas or propane: about $10 per million BTU at 17 cents per kWh with a COP of 5, versus about $18 for natural gas and $35 for propane at typical prices. Monthly cost depends on your climate, pool size, target temperature and whether you use a cover.
How long does a pool heat pump take to heat a pool?
Raising a cold pool by 10 to 20°F can take 24 to 72 hours depending on size, air temperature and the unit. After that it holds temperature with much shorter run times.
How long do pool heat pumps last?
Often 10 to 15 years or more with clean coils, good water chemistry and proper flow.
Do I need a bigger pool pump for a heat pump?
Not usually, but the pump must meet the heater’s minimum flow rate. Use the pool pump calculator to check your flow, and raise a variable-speed pump’s speed while heating if needed.
The 60-second call
If you want a warm pool all season and your air is usually above 50°F, a heat pump is the cheapest heat you can buy. Size it by surface area, put it on its own 230-volt circuit, use a cover, and get an itemized installed quote.