Water heater sizes by household
The same worksheet math, worked out per household: who showers in the busiest hour, what that costs in gallons, and the smallest gas and electric tanks whose first hour rating covers it. Every page shows the full table, both shower-head cases included.
By family size
Family of 1~26 gal peak hour: 30 gal gas, 30 gal electric.
Family of 2~46 gal peak hour: 30 gal gas, 40 gal electric.
Family of 3~66 gal peak hour: 40 gal gas, 80 gal electric.
Family of 4~66 gal peak hour: 40 gal gas, 80 gal electric.
Family of 5~86 gal peak hour: 75 gal gas, no single electric.
Family of 6~106 gal peak hour: 75 gal gas, no single electric.
Family of 7~126 gal peak hour: 75 gal gas, no single electric.
Family of 8~126 gal peak hour: 75 gal gas, no single electric.
By bedrooms
For buyers, landlords, and anyone sizing a house rather than a household: these pages plan for the occupancy the house can hold (bedrooms plus one), which is who the tank will serve over its 8-to-12-year life.
2-bedroom houseFull house is ~66 gal: 40 gal gas, 80 gal electric.
3-bedroom houseFull house is ~86 gal: 75 gal gas, no single electric.
4-bedroom houseFull house is ~106 gal: 75 gal gas, no single electric.
5-bedroom houseFull house is ~126 gal: 75 gal gas, no single electric.
None of these your house?
The calculator takes any busiest hour you can describe: baths, laundry, a dishwasher run, teenagers. Tankless households should size to simultaneous draw instead, on the tankless page.