The short answer
Most US homes still use a tank: in the 2020 Residential Energy Consumption Survey, 8.03 million of 123.5 million homes (6.5%) had a tankless main water heater. A tank is sized by first-hour rating and can run out in a long busy hour. A tankless heater is sized by flow at your winter rise and never runs out, but can't deliver more flow than it can lift.
Side by side
| Tank | Tankless | |
|---|---|---|
| Sized by | First-hour rating | Flow at your rise |
| Runs out | After the tank is used | Never, within its flow |
| Space | Floor-standing tank | Wall-hung box |
| Gas install | Smaller gas load | Larger gas load and its own vent |
Replacement timing
In the same survey, 36% of main water heaters were 10 or more years old: most decisions happen when an old tank fails.
Products mentioned
Questions readers ask
Is tankless better than a tank water heater?
It's different: endless hot water within its flow and less space, against a higher install load (gas line, vent or large electric circuits). Size it right for your winter rise.