4 Things to Know About Sizing a Pool Heater

Size your heater by pool volume, not guesswork Calculate your pool’s gallons first, then pick a heater that can raise the temperature by about 1°F per hour.

Match BTU output to pool size For a 20,000-gallon pool, choose a gas heater with roughly 100,000 BTU or a heat pump sized to your climate. Gas heaters heat fast for occasional use; heat pumps are cheaper for keeping the pool warm all season.

Avoid undersizing or oversizing Too small wastes energy and takes forever to heat. Slightly bigger is fine, but way too big causes short-cycling and faster wear.

Read actual BTU ratings, not model numbers Heat pumps are rated differently than gas heaters, so follow the manufacturer’s guidelines for your region. Ignore model number hype.