Water Heater Size Calculator — Gallons Needed

How the water heater sizing calculator works

Estimate peak-hour demand: ~12 gallons per person plus ~10 gallons per shower. Tank size ≈ first-hour rating × 0.7.

A 50-gallon tank with a 65-gallon first-hour rating covers most 4-person households with 2 morning showers.

Tankless never runs out but limits simultaneous fixtures by GPM. Tanks are cheaper upfront and easier to install.

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