Pool Heater Size Calculator
Find the right BTU rating for your pool heater based on surface area, temperature goals, and climate.
How Pool Heater Sizing Works
The BTU requirement is based on surface area heat loss: BTU/hr = Surface Area × Temp Rise × 12, then multiplied by a climate factor to account for ambient conditions and wind chill.
Gas heaters (natural gas or propane) heat water fastest and are ideal for pools that aren't heated continuously. Common sizes run from 100,000 to 400,000 BTU/hr.
Heat pumps are 3–5× more energy-efficient than gas but heat more slowly. They work best in ambient temperatures above 50°F. Common sizes range from 50,000 to 140,000 BTU/hr.
Electric resistance heaters are 100% efficient but expensive to operate. They are best suited for spas or small pools where gas is unavailable.