VouchedPros Tools

Water Heater Sizing Calculator

Find the right water-heater size by household — first-hour rating, tank gallons, and tankless GPM.

How this works. Sizing is based on the U.S. Department of Energy first-hour-rating (FHR) method — the gallons of hot water a heater delivers in a busy hour — at roughly 17 gallons per person. Match the FHR (not just tank size) to your peak hour, and prefer tankless GPM if showers, laundry, and the dishwasher overlap.

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