How Much Does It Cost to Run a Tankless Electric Water Heater?
Short answer: about $1.87 a day and $56.05 a month, or $3.11 for each hour it runs at full power, at the 2025 US average electricity rate. That is for a 18,000 W tankless electric water heater running 0.6 hours a day with a 100% duty cycle. Change the state and hours below for your own number.
Updated Nov 8, 2026
Quick answer
Quick answer, US average (17.3 c/kWh)
About $56.05 a month
The same use costs $38.26 a month in North Dakota and $131.51 in Hawaii. This appliance runs on a 240 V circuit, so plug-in meters will not fit it; use a panel monitor or the utility's hourly data instead.
- Per hour
- $3.11
- at 18,000 W
- Per day
- $1.87
- 0.6 h, 10.80 kWh
- Per month
- $56.05
- 30 days
- Per year
- $681.97
- 365 days at the same use
Your state, your hours
Per hour
$3.11
Per day
$1.87
Per month
$56.05
Per year
$681.97
Tankless Electric Water Heater at 18,000 W, 0.6 h a day, 30 days a month, 100% duty cycle: 324.0 kWh a month. Using the 2025 US average of 17.3 cents/kWh.
Want to change the watts or duty cycle too? Open the full calculator.
What decides the cost of running a tankless electric water heater
An electric tankless water heater has no tank to keep warm. It heats water only while a tap is open, with elements that switch on the instant flow starts. To do that it needs a lot of power at once: the 18 kW unit modeled here draws 18,000 W, about 75 A at 240 V, usually on two 40 A double-pole breakers. Whole-house units for cold climates are 27 to 36 kW and can need 112 to 150 A, which often means a service upgrade. A plug meter cannot measure any of this, since it is hardwired on a 240 V circuit.
Cost follows the hot water you use, not the size of the heater. The default here is 36 minutes a day at full power, 10.8 kWh, which is about what it takes to heat 60 gallons by 70 degrees, the same household figure used on the tank water heater page. At the national average rate that is about $1.87 a day, $56 a month or $682 a year. Electric tankless units turn nearly all of their electricity into hot water, so the only ways to lower the number are to use less hot water or heat it less.
Against a 50 gallon electric tank, tankless comes out slightly ahead. The tank on its own page uses about 13.5 kWh a day for the same household, and the 2.7 kWh gap is mostly standby loss, the heat a tank leaks keeping 50 gallons hot around the clock. That is worth about 47 cents a day, or roughly $170 a year. In winter, colder groundwater means a bigger temperature rise, so both heaters use more, and an undersized tankless unit responds by cutting flow at the tap.
The heat pump water heater is the option that really cuts the bill. It moves heat from the surrounding air instead of making it, using about a third of the electricity of resistance heating. On the same 60 gallons a day it uses roughly 4.5 kWh, well under half of a tankless unit, and it runs on a 30 A circuit instead of 75 A or more.
How to cut it
- Install low-flow shower heads. Flow rate sets both the power needed and the energy used.
- Set the outlet temperature to 120 degrees, not higher, so you are not mixing in cold water to cool it.
- Size it for your groundwater temperature. An undersized unit runs flat out and still cuts flow in winter.
- If you are replacing a tank to save money, compare a heat pump water heater first.
Tankless Electric Water Heater cost by state
Monthly cost for 18,000 W, 0.6 h a day, 100% duty cycle, 30 days, sorted cheapest to most expensive. Pick your state above to highlight it.
| Rank | State | Cents/kWh | Per month |
|---|---|---|---|
| 1 | North Dakota | 11.81 | $38.26 |
| 2 | Idaho | 11.82 | $38.30 |
| 3 | Nebraska | 12.34 | $39.98 |
| 4 | Louisiana | 12.57 | $40.73 |
| 5 | Arkansas | 12.84 | $41.60 |
| 6 | Montana | 12.98 | $42.06 |
| 7 | Utah | 13.07 | $42.35 |
| 8 | Washington | 13.11 | $42.48 |
| 9 | Oklahoma | 13.12 | $42.51 |
| 10 | Nevada | 13.15 | $42.61 |
| 11 | Tennessee | 13.18 | $42.70 |
| 12 | Kentucky | 13.24 | $42.90 |
| 13 | South Dakota | 13.38 | $43.35 |
| 14 | Wyoming | 13.38 | $43.35 |
| 15 | Missouri | 13.49 | $43.71 |
| 16 | Iowa | 13.72 | $44.45 |
| 17 | North Carolina | 14.02 | $45.42 |
| 18 | Mississippi | 14.03 | $45.46 |
| 19 | Kansas | 14.56 | $47.17 |
| 20 | Georgia | 14.73 | $47.73 |
| 21 | South Carolina | 14.96 | $48.47 |
| 22 | New Mexico | 15.08 | $48.86 |
| 23 | Florida | 15.24 | $49.38 |
| 24 | Virginia | 15.28 | $49.51 |
| 25 | Arizona | 15.32 | $49.64 |
| 26 | Oregon | 15.37 | $49.80 |
| 27 | West Virginia | 15.41 | $49.93 |
| 28 | Texas | 15.47 | $50.12 |
| 29 | Minnesota | 15.82 | $51.26 |
| 30 | Colorado | 15.85 | $51.35 |
| 31 | Alabama | 16.10 | $52.16 |
| 32 | Indiana | 16.23 | $52.59 |
| 33 | Ohio | 16.96 | $54.95 |
| 34 | Delaware | 17.13 | $55.50 |
| 35 | Illinois | 17.69 | $57.32 |
| 36 | Wisconsin | 18.16 | $58.84 |
| 37 | Pennsylvania | 19.30 | $62.53 |
| 38 | Maryland | 19.48 | $63.12 |
| 39 | Michigan | 20.01 | $64.83 |
| 40 | District of Columbia | 21.94 | $71.09 |
| 41 | New Jersey | 22.63 | $73.32 |
| 42 | Vermont | 22.92 | $74.26 |
| 43 | New Hampshire | 24.56 | $79.57 |
| 44 | Alaska | 26.09 | $84.53 |
| 45 | New York | 26.39 | $85.50 |
| 46 | Maine | 27.78 | $90.01 |
| 47 | Connecticut | 29.38 | $95.19 |
| 48 | Rhode Island | 29.46 | $95.45 |
| 49 | Massachusetts | 30.48 | $98.76 |
| 50 | California | 32.54 | $105.43 |
| 51 | Hawaii | 40.59 | $131.51 |
Rates: U.S. Energy Information Administration, Form EIA-861, annual average residential price, 2025 (eia.gov). Full list on the electricity rates by state page.
Cheaper to run
The swap that cuts this bill the most, from the products we track. Specs come from the listing or the maker.
Rinnai REHP50 50-gallon heat pump water heater
- ENERGY STAR
- electric
- 30 A of breakers
- 50 gallons
+3 moreFewer
- 73 gal first hour
- 240V / 30 A
- 10-year tank and parts warranty
A 50 gallon heat pump water heater rated 3.75 UEF and ENERGY STAR certified. It runs on a 240V / 30 A circuit instead of the 75 A or more an electric tankless unit needs, and uses roughly a third of the electricity of resistance heating.
- 3.75 UEF, ENERGY STAR certified
- 73 gallons first-hour delivery
- Runs on a 240V, 30 A circuit
- A tank, so it needs floor space
- 1-year labor warranty
$1,000 to $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Some links pay us a commission; that does not decide what we show. Not lab tested. See our disclosure.
Frequently asked questions
How much does it cost to run a tankless electric water heater per month?+
About $56 a month for a household using about 60 gallons of hot water a day. An 18 kW unit running 36 minutes a day at full power uses 18 x 0.6 = 10.8 kWh, or 324 kWh over 30 days, and 324 x $0.173 is about $56.
How much does it cost to run a tankless water heater per day?+
About $1.87 a day. 10.8 kWh, enough to heat about 60 gallons by 70 degrees, times $0.173 is $1.87 at the national average rate.
How much does it cost to run a tankless electric water heater per year?+
About $682 a year. 10.8 kWh a day for 365 days is 3,942 kWh, and 3,942 x $0.173 is about $682. At the cheapest state rate of about 11.8 cents it is about $466, and in Hawaii at about 40.6 cents it is about $1,600.
How much does a tankless water heater cost per hour?+
About $3.11 for each hour at full power. An 18 kW unit uses 18 kWh an hour at full output, and 18 x $0.173 is $3.11, or about 5.2 cents a minute. It reaches full power only at high flow or with cold incoming water.
How much does a shower cost with a tankless electric water heater?+
About 42 to 50 cents for a 10 minute shower. At 2 gallons per minute that is 20 gallons, and heating 20 gallons by 50 to 60 degrees takes about 2.4 to 2.9 kWh at 17.3 cents per kWh.
How many watts and amps does a tankless electric water heater use?+
18,000 W and about 75 A at 240 V for the 18 kW unit modeled here, typically wired to two 40 A double-pole breakers. Whole-house models of 24 to 36 kW draw 100 to 150 A, and many homes need a 200 A service to support one.
Is a tankless electric water heater cheaper to run than a tank?+
Yes, slightly, by about $170 a year. For the same 60 gallons a day a 50 gallon electric tank uses about 13.5 kWh, about $2.34 a day, and a tankless unit about 10.8 kWh, about $1.87. The 2.7 kWh daily gap is the tank's standby loss, about 985 kWh a year at 17.3 cents per kWh.
Tankless vs heat pump water heater: which costs less to run?+
The heat pump water heater, by more than half. For 60 gallons a day it uses roughly 4.5 kWh, about 78 cents a day or $23 a month, against 10.8 kWh and about $56 a month for an electric tankless unit.
Does a tankless electric water heater use a lot of electricity?+
Yes, in two ways. Its 18 to 36 kW draw while running is the largest instantaneous load in most homes, and at about 10.8 kWh a day for a typical family it uses more than eight times what a refrigerator does (1.26 kWh a day). Only space heating, cooling and EV charging usually use more.
Can a generator or battery run a tankless electric water heater?+
No, not practically. An 18 kW, 75 A load is far beyond portable generators and power stations, and it would empty a 13.5 kWh home battery in under an hour at full power. Leave it off backup circuits.
Marcus Reed
Founder and Editor, CrunchYourDollars
Marcus Reed builds the sizing tools on CrunchYourDollars. He is a software engineer with a long-running PC hardware and power supply habit, which is where the watts, watt-hours and surge math on this site comes from. Product specs are pulled from manufacturer data sheets, electricity rates from the U.S. Energy Information Administration, and water chemistry rules from the Water Quality Association. He is not a licensed electrician or plumber: the tools show the math and the matching models so you can make the call, and anything involving your electrical panel should be checked by a licensed pro.
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