What size water heater for a family of 8?
A household of 8 is where tank sizing gets honest. Even the staggered case (6 showers in the busiest hour) pulls 126 gallons, which is a 75-gallon gas tank and past every single electric tank made. All 8 in one hour is 126 gallons. The realistic menu: big gas, two tanks, a tankless sized to simultaneous draw, or a family shower schedule with teeth.
Every version of the busiest hour, for 8 people
Each row is that many showers in one hour plus one shave and one round of hand dishes, priced in hot gallons off the DOE/AHRI worksheet (20 per standard shower, 13 on a 2.0 GPM low-flow head). The tank shown is the smallest standard size whose first hour rating covers the demand; our FHR figures are ~70% of tank volume plus an hour of recovery, and label values land within a few gallons of them.
| 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 |
| 4 | 86 gal | 75 gal | none fits | 58 gal | 40 gal | 65 gal |
| 5 | 106 gal | 75 gal | none fits | 71 gal | 50 gal | 80 gal |
| 6 | 126 gal | 75 gal | none fits | 84 gal | 75 gal | none fits |
The "none fits" cells are the point of this page. An electric element recovers about 20 gallons an hour, so past roughly three standard back-to-back showers the stored gallons are doing all the work, and the biggest residential electric tank (80 gallons, FHR about 76) simply runs dry. Gas recovers at 43 gallons an hour and a 75-gallon gas at 80, which is why big households skew gas or tankless.
Questions people ask
Is a 50-gallon water heater enough for a family of 8?
Not on its own. 6 showers plus sink use is 126 gallons, and a 50-gallon tank delivers about 78 (gas) or 55 (electric) gallons in the hour. A 50 works here only if the household genuinely spreads showers across the day.
Do these numbers change with teenagers?
Only in the honest direction. The worksheet's 20-gallon shower is a 10-minute shower on a 2.5 GPM head; a teenager's 25-minute shower is 50 gallons all by itself. If that is your house, count long showers as two.
What about a tankless for a family of 8?
It sidesteps the peak-hour problem entirely, because a tankless never runs out; it just caps how many fixtures run at once. See the tankless answer for this household.