How Much Does It Cost to Run a Tankless Water Heater Today?

Source: Planning watts of 18,000 and 0.5 hours a day, hours a day of actual hot water flow. Price: 17.23 cents per kWh, the 2025 US residential average from EIA Form EIA-861.

The monthly cost is 31% of the $150.68 average US electric bill. It runs all year, so the yearly cost is twelve times the monthly figure.

One figure cannot fit every home. These three cases show how much the answer moves with the equipment and the hours.

The lowest case costs $10 a month and the highest $141. Use the calculator above to match your own.

The same tankless water heater costs different amounts depending on the state, because the price per kWh differs. Here are the three cheapest states, the US average and the three costliest, for the same 274 kWh a month.

Source: U.S. Energy Information Administration, Form EIA-861 (final 2025 data). Price is residential revenue divided by sales and includes fixed charges.

See electricity rates in every state to find your own.

An electric tankless heater has no tank to keep warm. It heats water only while a tap is open, but it must deliver a large amount of power at that moment, which is why electrical capacity is the main design question.

The unit size, the temperature rise and the number of simultaneous uses all matter, and a whole-home unit may require a larger electrical panel and heavy wiring.

For scale, the EIA Residential Energy Consumption Survey found the average US home used about 105 kWh a month on water heating in 2020, and the average detached house about 104 kWh. These averages include homes with no such equipment, so a home that has it uses more.

The range for this kind of appliance runs from about 10,000 to 27,000 watts. At 0.5 hours a day that is $26 to $71 a month, which is why checking the label on yours is worth the minute.

• Have an electrician confirm your panel and wiring can handle the draw.
• Shorten the run to the farthest tap.
• Compare against a heat pump tank, which can cost less to run.

Next step: Electric water heater costs. For general ideas, read how to lower your electric bill.

Other appliances in the water group: Electric Water Heater, Well Pump, Sump Pump.

The cost is watts divided by 1,000, times hours, times your price per kWh. The 18,000 watts is a planning figure for this kind of appliance, set from typical product ratings, and the 0.5 hours is an assumed day of use. Neither is copied from a federal table. Federal guidance describes the method and warns that real wattage varies, so we publish our own typical ranges and label them as such. Prices come from EIA Form EIA-861 for 2025.

The calculation is the standard one used in the U.S. Department of Energy's consumer guidance on estimating appliance energy use. Wattage varies by product age and features, so the label on your own appliance beats any average. Read more in our methodology.