What size water heater for a 2-bedroom house?
Size the house, not the current tenants: a 2-bedroom holds 3 people by the usual planning count (bedrooms plus one), and a full-house morning there runs about 66 gallons of hot water. That takes a 40 gal gas tank or a 80 gal electric. A calmer household can step down the table below.
From full house to quiet couple, in gallons
Rows run from every bed filled and everyone showering in the same hour down to one shower. Each row carries one shave and one round of hand dishes (6 gallons of sink use). The full-house row is what this house can demand of the tank; where you actually live on the table is a judgment call the next owner may not share.
| Showers in the hour | Peak demand | Gas tank | Electric tank | Demand, 2.0 GPM heads | Gas | Electric |
|---|---|---|---|---|---|---|
| 1 | 26 gal | 30 gal | 30 gal | 19 gal | 30 gal | 30 gal |
| 2 | 46 gal | 30 gal | 40 gal | 32 gal | 30 gal | 30 gal |
| 3 | 66 gal | 40 gal | 80 gal | 45 gal | 30 gal | 40 gal |
The spread between gas and electric is recovery: a gas burner puts back about 43 gallons an hour while an element manages 20, so gas covers a 2-bedroom's full-house morning with a 40-gallon tank while electric needs 80 gallons of storage to do the same job.
Questions people ask
What size water heater comes standard in a 2-bedroom house?
Builders typically install a 40 or 50-gallon tank in a 2-bedroom house because it is the cheap default, not because anyone ran the numbers. At full occupancy (3 people) that default holds up fine on gas.
Should I size for the bedrooms or for who lives here now?
Bedrooms, if the tank will outlive the current household. A tank runs 8 to 12 years; a 2-bedroom house can hold 3 or more for most of that. Sizing to a couple in a 2-bedroom house saves maybe $100 today and gets re-bought by the next full household.
Does a spare bathroom change the size?
Not for a tank. Tank sizing counts gallons in the busiest hour, and an extra bathroom does not shower anybody extra; it just lets two showers happen at once, which is a tankless-sizing (GPM) problem, not a gallons problem.