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How many watts does a tankless water heater use? (18,000 W)
A tankless water heater uses about 18,000 W
Typical range 10,000–36,000 watts.
Typical range 10,000–36,000 watts.
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An electric tankless heater heats water instantly on demand, so it draws enormous power but only while a hot tap is running.
Tankless water heater power specs
| Typical running power | 18,000 W |
| Typical range | 10,000–36,000 W |
| Energy use | 18.00 kWh/day · 540.0 kWh/mo |
What affects a tankless water heater's wattage
A tankless water heater is rated around 18,000 W, but the real figure shifts with a few things:
- Model and rating: A tankless water heater ranges from about 10,000 W on efficient units to 36,000 W on larger or older ones — a spread of ~26,000 W.
- Usage: the real draw depends on the heat setting and run time.
- Run time: because a tankless water heater typically runs about 1 h/day, hours of use matter as much as raw wattage on your bill.
Running cost at $0.17/kWh
| Electricity rate | Per day | Per month | Per year |
|---|---|---|---|
| $0.10/kWh | $1.80 | $54.00 | $657.00 |
| $0.15/kWh | $2.70 | $81.00 | $985.50 |
| $0.20/kWh | $3.60 | $108.00 | $1,314.00 |
| $0.25/kWh | $4.50 | $135.00 | $1,642.50 |
| $0.30/kWh | $5.40 | $162.00 | $1,971.00 |
| $0.40/kWh | $7.20 | $216.00 | $2,628.00 |
See the full breakdown of what it costs to run a tankless water heater, or what size power station runs a tankless water heater.
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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