Water Heater Sizing Calculator — Tank & Tankless
Is first-hour rating or recovery rate more important?
First-hour rating (FHR) matters most for households with concentrated peak demand, since it reflects storage plus one hour of heating. Recovery rate matters more for steady, all-day use. The DOE requires the FHR on the EnergyGuide label — match it to your peak-hour demand and you will rarely run out. Verify the final selection against the manufacturer data and local code.
Run the numbers for your project
Use the Water Heater Sizing Calculator — Tank & Tankless to get an exact answer for your inputs.
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