How Do I Calculate Water Heater Size

Measure the amount of water and multiply by 60 to get the gallons per minute (or liters per minute). The flow rate through the demand water heater should be at least 3.25 gallons (12.3 liters) per minute. To reduce flow rates, install low-flow water fixtures.

How do I determine what size water heater I need?

1. 1 or 2 people—23 to 36 gallons.
2. 2 to 4 people—36 to 46 gallons.
3. 3 to 5 people—46 to 56 gallons.
4. 5 or more people—over 56 gallons (add 10 gallons per additional person)

Is a 50 gallon water heater enough for a family of 4?

For a four-person family, a 50-gallon water heater is sufficient. 50-gallons is good if you’re using electricity, and 40 gallons will work for natural gas or propane. Families with more than five persons may benefit from an 80-gallon electric water heater or 50-gallon gas water heater.