How Much Does It Cost to Run a Tankless Electric Water Heater?
A whole-home tankless electric unit draws a massive 18,000+ watts — but only during the minutes hot water is actually flowing, with zero standby loss. At the US-average rate of 16.5¢/kWh, running a tankless electric water heater costs about $36.09/month ($433.09/year) at typical use. Adjust the watts, hours, and your rate below for your exact number.
Cost to run a tankless electric water heater
$433/yr
- Per day
- $1.19
- Per month
- $36.09
- Energy per year
- 2,628 kWh
Cost = power (kW) × hours × days × your rate. Defaults are typical values — enter your appliance's actual watts (often on a label) and your real rate for a precise figure.
How much electricity does a tankless electric water heater use?
At 18,000 W for 0.4 hours a day, a tankless electric water heater uses about 7.2 kWh per day — roughly 219 kWh per month and 2,628 kWh per year. That's about 25% of the 863 kWh the average US home uses in a month. Energy use is the same everywhere — only the price per kWh changes your bill.
Wondering about the circuit instead? See how many amps a tankless electric water heater draws.
Cost to run a tankless electric water heater by electricity rate
Same 18,000 W appliance, 0.4 h/day — the bill changes with where you live.
| Scenario | Rate | Per month | Per year |
|---|---|---|---|
| Cheapest states (North Dakota) | 11.5¢ | $25.21 | $302.48 |
| US average | 16.5¢ | $36.09 | $433.09 |
| Most expensive (Hawaii) | 42.9¢ | $93.86 | $1,126.36 |
Find your state's rate on the electricity rates by state page, or see the appliance wattage chart for more devices.
Measure what a tankless electric water heater really costs you
The estimate above uses typical wattage and hours. This load is usually hardwired or on a 240 V circuit, so a plug-in meter won't fit it; a whole-home monitor's sensors clip onto the circuit's wires inside the panel and log its real kilowatt-hours. That means working in a live panel — hire an electrician if that isn't you.
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Whole-home energy monitor
Emporia Vue 3 Home Energy Monitor (16 circuit sensors)
Best for: Measuring hardwired and 240 V loads, or every circuit at once
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