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What size generator or power station for a tankless water heater? (22,500+ W)
To run a tankless water heater, choose at least
22,500 W running.
22,500 W running.
A tankless water heater draws about 18,000 W while running. Pick a generator, inverter or power station rated comfortably above these numbers.
Battery runtime calculator
Estimated runtime—
Assumes about 85% usable capacity. Motors need extra headroom for startup surge.
How long a power station lasts
| Power station | Estimated runtime |
|---|---|
| 300 Wh | 0 h 1 min |
| 500 Wh | 0 h 1 min |
| 1,000 Wh | 0 h 3 min |
| 2,000 Wh | 0 h 6 min |
| 3,000 Wh | 0 h 9 min |
Sizing guide
| Minimum running watts | 22,500 W |
| Minimum starting watts | 22,500 W |
| Suggested inverter | 22,500 W or higher |
See also tankless water heater wattage and running cost.
FAQ
How many watts does a tankless water heater use?
Whole-home electric tankless units draw 10,000-36,000 watts while running.
Do tankless heaters save money?
They cut standby losses, but the high draw needs a heavy electrical service.
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