Heater Size Calculator
Calculates required heater capacity (BTU/hour) based on pool volume, temperature rise, and timeframe.
How it works
BTU/h = (Gallons × 8.34 × Temp Rise °F) ÷ Heating Hours + 25% bufferPool cover reduces requirement ~30%
- You enter
- Pool volume (gallons), current water temp (°F), target water temp (°F), heat-up hours, pool cover (yes/no), heater type
- You get
- Required BTU/hour, heater size recommendation, cost/month estimate, heat pump COP efficiency
How accurate is it? Assumes continuous operation; actual performance varies by weather/wind/cover/humidity; heat pump COP 3.5-5.0.
These are estimates, not quotes. See How We Estimate.
Worked example
15,000 gal pool 60°F→75°F (15° rise) in 24 hours: (15000×8.34×15)÷24 = 77,062 BTU + 25% = ~96,000 BTU heater.
Tap an example above the calculator to see it worked with live numbers.
Reference table
| Heater | Assumed efficiency |
|---|---|
| Gas heater | 84% efficient |
| Heat pump | COP 5 (5 units of heat per unit of power) |
| Heat to warm water | 8.34 BTU per gallon per °F |
When to use it
Determines appropriate heater capacity (gas, heat pump, electric) to achieve desired water temperature in reasonable time.
Initial heater selection, heater upgrade, seasonal temperature maintenance, extending swim season.