Pool Heater Size Calculator

How to Use This Calculator

1. Enter pool volume in gallons.
2. Enter the desired temperature rise (e.g., 65°F → 80°F = 15°F rise).
3. Enter the heat-up time in hours.
4. Results show required BTU/hr, heater size tier, and recovery time. Use Extended tabs for gas, heat pump, and heat loss detail.

Formula

Example

Frequently Asked Questions

• How many BTUs do I need to heat my pool? ▼
  Multiply the pool volume in gallons by 8.34 (lbs/gal) by the desired temperature rise in °F, then divide by the number of hours you want to heat. For example, a 15,000-gallon pool needing a 20°F rise in 24 hours requires about 104,250 BTU/hr.
• What is the difference between a gas heater and a heat pump? ▼
  A gas heater burns natural gas and can heat a pool quickly regardless of air temperature. A heat pump is 4–6× more efficient electrically but works best when air temperature is above 50°F. Heat pumps heat slowly (1–3°F per hour) while gas heaters heat faster (5–10°F per hour).
• How much does a pool cover save? ▼
  A solar or bubble cover can reduce heat loss by 50–70%. For most pools, surface evaporation accounts for 70% of heat loss, so covering the pool overnight dramatically reduces heater run time and cost.
• What pool heater size do I need for a typical residential pool? ▼
  A standard 15,000–20,000 gallon in-ground pool typically needs a 150,000–400,000 BTU/hr gas heater, or a 100,000–125,000 BTU/hr heat pump, depending on climate, desired temperature rise, and heat loss.

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