01
The purpose
What does this calculator estimate?
Size a heat pump to your pool's surface heat loss and climate — plus its real electricity draw.
Heating & Energy · D2
Pool Heat Pump Sizing Calculator
Size a heat pump to your pool's surface heat loss and climate — plus its real electricity draw.
Measure the inputsHeat pumps shine in mild, warm climates where their COP stays high (4–5.5).
Read the full resultBelow about 50°F air, heat pump efficiency drops sharply — gas may win in cold snaps.
Check the boundaryA solar cover roughly triples a heat pump's practical effectiveness by cutting losses.
Useful forHeating & EnergyPlanningComparisonVerification
Live calculation
Heat pump inputs
✓ Checked May 2026
Enter surface area, temperatures, and cover use.
Calculated result
—
Enter the required values to calculate.
Enter the known values. Let the engine handle the calculation.
✓ Formula checked↻ Live result○ No account needed
Planning estimate only. Confirm product labels, equipment specifications, qualified-professional advice and local requirements before acting.
The result, explained
Use the Pool Heat Pump Sizing Calculator result with context.
Size a heat pump to your pool's surface heat loss and climate — plus its real electricity draw.
02
The tool
What information does it use?
- Pool volume: enter a measured or verified value
- Pool surface area: Length × width of the water surface.
- Target water temp: enter a measured or verified value
- Average air temp: Outdoor air during heating season.
- Using a solar cover?: A cover cuts heat loss ~65%.
03
The method
How to use this calculator
- Pool volumeEnter the value you can verify.
- Pool surface areaLength × width of the water surface.
- Target water tempEnter the value you can verify.
- Average air tempOutdoor air during heating season.
- Using a solar cover?A cover cuts heat loss ~65%.
04
The relationship
The formula in plain English
Heat load = Surface area × (Target − Air temp); kW = load ÷ (3412 × COP)
COP rises in warm air (~5.5) and falls in cold (~2.5). A cover multiplies the load by 0.35.05
Worked through
A worked example: 500 sq ft pool, target 82°F, air 60°F, no cover
- Temp diff = 82 − 60 = 22°F
- Heat loss = 500 × 22 × 1.0 = 11,000 BTU/hr
- COP 4.5 → kW = 11,000 ÷ (3412 × 4.5) = 0.72 kW
| Air temp | Est. COP | Heat loss BTU/hr* | Electric draw |
|---|---|---|---|
| 75°F | 5.5 | 3,500 | 0.19 kW |
| 70°F | 4.5 | 6,000 | 0.39 kW |
| 60°F | 4.5 | 11,000 | 0.72 kW |
| 55°F | 3.5 | 13,500 | 1.13 kW |
| 48°F | 2.5 | 17,000 | 1.99 kW |
06
Why it matters
How the result supports the next decision
Heat pumps shine in mild, warm climates where their COP stays high (4–5.5).
Below about 50°F air, heat pump efficiency drops sharply — gas may win in cold snaps.
07
Good inputs
Improve the estimate before relying on it
- Heat pumps shine in mild, warm climates where their COP stays high (4–5.5).
- Below about 50°F air, heat pump efficiency drops sharply — gas may win in cold snaps.
- A solar cover roughly triples a heat pump's practical effectiveness by cutting losses.
- Heat pumps heat slowly but cheaply — pair with a cover and run continuously.
- Size to maintenance load (holding temp), not rapid heat-up, for heat pumps.
08
The boundary
How to interpret the result
Measurements, equipment specifications, site conditions and local requirements can change the practical result.
The engine reports invalid inputs and safety warnings beside the result. Resolve those messages before using the estimate.
09
Before acting
What should override this estimate?
- Measured site conditions and current test results
- Product labels and manufacturer specifications
- Qualified-professional advice and applicable local codes
10
Common questions
Frequently asked questions
How do I size a pool heat pump?
Size it to your pool's surface heat loss, which is roughly the surface area times the gap between target water and average air temperature. That gives the BTU per hour the heat pump must replace to hold temperature. Because heat pumps heat slowly, you size to this maintenance load rather than to a fast heat-up.
What is COP on a pool heat pump?
COP, the coefficient of performance, is how many units of heat the pump moves per unit of electricity it uses. A COP of 5 means five times more heat out than electricity in. COP rises in warm air — around 5.5 above 70°F — and falls in cold air, dropping toward 2.5 below 50°F.
Are heat pumps cheaper than gas heaters?
To run, yes, usually much cheaper, because a COP of 4 to 5 means they deliver four to five times the heat per dollar of electricity compared to resistance heating, and they often beat gas per BTU in mild climates. The trade-offs are a higher purchase price and slow heat-up.
How cold can a pool heat pump work?
Most pool heat pumps keep working down to about 45 to 50°F air temperature, but their efficiency falls as it gets colder, so they heat more slowly and cost more per BTU. In climates with cold snaps, owners sometimes pair a heat pump with a gas heater for fast recovery.
Does a solar cover help a heat pump?
Enormously. Since heat pumps heat slowly and a pool's biggest heat loss is evaporation from the surface, a cover that cuts loss by around 65 percent lets a modest heat pump easily hold temperature. Without a cover, the same pump may never catch up on a breezy night.
What size heat pump for a 15,000 gallon pool?
For a 500 sq ft surface and a 20°F air gap, roughly a 100,000–125,000 BTU heat pump; size to surface heat loss.
Is a pool heat pump worth it?
In mild and warm climates, yes — low running cost offsets the higher purchase price over a few seasons.
How much electricity does a pool heat pump use?
At a COP of 5, replacing 50,000 BTU/hr draws about 2.9 kW — far less than resistance heating.
Primary sources
Use the result with current guidance.
These official references support safe planning context. Product labels, local requirements and qualified-professional advice take priority over a general calculator estimate.