🛁 Water Heater Size Calculator

📊 Tank Size Guidelines

📚 Tankless vs Tank Sizing

Tank Water Heaters: Size is measured in gallons. First Hour Rating (FHR) indicates how many gallons can be heated in an hour during peak demand.

Tankless Water Heaters: Sized by flow rate (GPM) and temperature rise. A family of 4 typically needs 8-10 GPM in cold climates.

⚡ Sizing Formula

Basic calculation for tank storage:

• 10 gallons per occupant (minimum)
• Plus 10 gallons per bathroom
• Plus 20% for cold climates
• First Hour Rating = Tank size × 1.5 to 2.0 (varies by recovery rate)

⚠️ Important Considerations

• Consider simultaneous use patterns in your household
• Larger tanks provide buffer for unexpected guests
• Higher recovery rate heaters can be smaller if usage is staggered
• Always consult a licensed plumber for final sizing