Is a tankless electric water heater expensive to run?

The energy saving versus a tank is modest; the bigger issue is panel capacity — 18 kW needs 75+ amps of breaker space. At typical use it adds about $36.09 to a monthly electric bill at the US-average rate, but that swings from $25.21 in the cheapest states to $93.86 in the most expensive.

How many watts does a tankless electric water heater use?

Tankless Electric Water Heater typically draws about 18,000 running watts. It's a resistive load, so its startup and running wattage are the same. Check the nameplate or label on your specific unit for its exact rating.

How can I lower the cost of running a tankless electric water heater?

The energy saving versus a tank is modest; the bigger issue is panel capacity — 18 kW needs 75+ amps of breaker space. You can also cut the cost by lowering your electricity rate — many utilities offer cheaper off-peak hours — or simply by running it fewer hours. Use the calculator above to see how changing hours per day or your rate moves the number.

How Much Does It Cost to Run 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.

Power (watts)

Hours per day: 0.4

Days per week: 7

Your state (sets the rate)

Electricity rate ($/kWh)

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.

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.

Frequently asked questions

At the US-average residential rate of 16.5¢/kWh, a tankless electric water heater drawing 18,000 watts for about 0.4 hours a day costs roughly $1.19 per day, $36.09 per month, and $433.09 per year. Your actual cost depends on your electricity rate and how much you use it — adjust both in the calculator above.

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How Much Does It Cost to Run Tankless Electric Water Heater?

Cost to run a tankless electric water heater by electricity rate

Frequently asked questions

How much does it cost to run a tankless electric water heater?

Is a tankless electric water heater expensive to run?

How many watts does a tankless electric water heater use?

How can I lower the cost of running a tankless electric water heater?

Cost to run other appliances