Estimate BTU/hr needed for your target temperature rise and time.
This calculator estimates the BTU-per-hour capacity needed to raise a pool’s temperature by a selected number of degrees within a selected amount of time. Enter the pool volume, desired temperature increase, heating time, and estimated heater efficiency.
The calculation first estimates the total energy required to heat the water, then divides that energy by the target heating time. The efficiency setting increases the required heater input to account for energy lost during operation.
An undersized heater may take too long to reach the target temperature, especially in cool or windy weather. A larger heater can raise water temperature faster, but it may require larger gas lines, electrical service, plumbing capacity, and higher installation cost.
This is water-only sizing math. It does not fully account for evaporation, wind, nighttime cooling, ground loss, uncovered surface area, plumbing heat loss, or changing weather. Real heater sizing should include the pool’s surface area, climate, and intended use.
It uses more fuel per hour, but it may run for fewer hours. Total cost depends on the desired temperature rise, heat loss, efficiency, and runtime.
Yes. Equipment and plumbing must support the heater, and local codes or utility service may limit available gas or electrical capacity.
That depends on how the pool will be used. Occasional rapid heating usually needs more capacity than maintaining a steady temperature under a cover.
A cover reduces evaporation and heat loss. It may not change the heater’s nameplate size, but it can greatly improve heating time and operating cost.
Do not buy a heater from gallons alone. Think about how fast you want the pool heated, your local weather, cover use, and whether the gas or electrical service can support the equipment.