Water Heater Sizing Calculator
Tank Water Heater Size
Calculate tank capacity based on peak hour demand
Tankless Water Heater Size
Calculate flow rate needed for tankless unit
Formula
Peak Hour Demand = Daily Use x 0.7 | First Hour Rating = Tank x 0.7 + Recovery Rate
Frequently Asked Questions
What size water heater do I need?
For 1-2 people, 30-40 gallons. For 3-4 people, 40-50 gallons. For 5+ people, 50-80 gallons. This varies by usage habits and fuel type.
Tank vs tankless water heater?
Tank heaters store hot water and are cheaper upfront. Tankless heaters heat on demand, are more efficient, but cost more. Tankless is sized by flow rate (GPM) and temperature rise.
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