Pool Heater Energy and Time Calculator
Estimate what it takes to warm your pool. Enter the gallons, the temperature rise you want, your heater output and its efficiency to see the energy in BTU and kWh plus the heating time.
How to calculate pool heating
- Enter your pool volume in gallons.
- Set the temperature rise you want, in degrees Fahrenheit.
- Enter your heater output in BTU per hour to estimate the time.
- Adjust the efficiency, then read the energy and hours needed.
Examples
Heat 20,000 gallons by 10F
20,000 gallons, +10F, 400,000 BTU/hr heater
About 1,669,081 BTU (489 kWh), roughly 4.17 hours
Frequently asked questions
How much energy does it take to heat a pool?
One BTU raises one pound of water by one degree Fahrenheit. A US gallon weighs about 8.345 lb, so the energy is gallons times 8.345 times the rise in degrees.
How long will my heater take?
Divide the total BTU needed by the heater's BTU per hour. A 400,000 BTU per hour heater warming 20,000 gallons by 10F takes about 4.17 hours.
Why does efficiency matter?
No heater turns all its fuel into pool heat. Dividing by the efficiency adds the lost energy, so an 80 percent heater needs about 25 percent more input.
How do I convert BTU to kWh?
One kilowatt hour equals 3,412.142 BTU. The tool divides the BTU by that figure so you can compare with an electric heat pump or your power bill.
Does covering the pool help?
Yes. A cover sharply cuts evaporation, the largest heat loss. This tool sizes the heat-up energy; a cover reduces the energy to hold that temperature.
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