DOE hot-water use by fixture (gallons per use + GPM)
Typical published planning values — NOT a certified spec or professional advice. Efficiency, sizing and life vary by unit and installation; confirm on the EnergyGuide label and the manufacturer’s instructions. Water-heater installation, gas, venting, combustion, the temperature-&-pressure relief valve, and the scald / Legionella tradeoff of a temperature setting are a licensed plumber / gas fitter, manufacturer-instruction and local-code matter — not engineered here.
This companion table gives the LABELED DOE hot-water use per fixture (gallons per use) and the fixture flow (GPM) — the other half of the sizing method. Add up the uses in your busiest hour for a tank’s First-Hour Rating, and add the simultaneous GPM for a tankless. Measure your own routine. It backs the peak-hour-demand calculator and the tankless sizing calculator.
| Fixture / use | Gallons per use | Flow (GPM) |
|---|---|---|
| Shower | ~20 | ~2.0 |
| Bath (tub) | ~20 | ~2.0 |
| Shaving | ~2 | ~1.5 |
| Hand / face wash | ~4 | ~1.5 |
| Hair shampoo (sink) | ~4 | ~1.5 |
| Hand dishwashing | ~4 | ~1.5 |
| Automatic dishwasher | ~6 | ~1.5 |
| Food prep | ~5 | ~1.5 |
| Clothes washer | ~7 | ~2.0 |
LABELED DOE planning snapshot — measure your actual routine. Add up the uses in your busiest hour for a tank’s First-Hour Rating; add the simultaneous GPM for a tankless. Snapshot: 2026-07-13.