utility · 18000W typical
Running a tankless electric water heater costs about $4.46/month.
That's the typical tankless electric water heater at 18000W, run 1 hours a day at the US-average rate of 16.5¢/kWh. Change any of those and the number moves — use the calculator below to see yours.
Estimated cost
A tankless electric water heater draws full power only while the thermostat/compressor is running — about 0.1 effective hours at 18000W across your 1-hour window.
How you use it
Cost shifts with how long it's on.
The same tankless electric water heater can cost very different amounts depending on usage patterns. Three common scenarios, at the US-average rate.
family household
$4.46
per month
on-demand heating during hot-water use
couple
$2.23
per month
shorter on-demand cycles
Where you live
$8.07 spread between the cheapest and priciest states.
Same appliance, same hours of use, different zip code — the monthly cost varies this much.
| State | Rate | Monthly | Yearly |
|---|---|---|---|
| Hawaii | 41.2¢ | $11.12 | $135.34 |
| California | 31.4¢ | $8.48 | $103.15 |
| Massachusetts | 30.8¢ | $8.32 | $101.18 |
| Connecticut | 28.7¢ | $7.75 | $94.28 |
| Rhode Island | 27.9¢ | $7.53 | $91.65 |
| New Hampshire | 24.6¢ | $6.64 | $80.81 |
| Alaska | 24.3¢ | $6.56 | $79.83 |
| New York | 22.3¢ | $6.02 | $73.26 |
| Maine | 22.1¢ | $5.97 | $72.60 |
| Vermont | 21.5¢ | $5.81 | $70.63 |
| Michigan | 19.3¢ | $5.21 | $63.40 |
| New Jersey | 19.1¢ | $5.16 | $62.74 |
| Maryland | 18.4¢ | $4.97 | $60.44 |
| Pennsylvania | 18.1¢ | $4.89 | $59.46 |
| District of Columbia | 17.8¢ | $4.81 | $58.47 |
| Wisconsin | 17.4¢ | $4.70 | $57.16 |
| Delaware | 17.2¢ | $4.64 | $56.50 |
| Illinois | 16.9¢ | $4.56 | $55.52 |
| Ohio | 16.6¢ | $4.48 | $54.53 |
| Nevada | 16.3¢ | $4.40 | $53.55 |
| Indiana | 15.8¢ | $4.27 | $51.90 |
| Virginia | 15.7¢ | $4.24 | $51.57 |
| Minnesota | 15.6¢ | $4.21 | $51.25 |
| Colorado | 15.4¢ | $4.16 | $50.59 |
| Alabama | 15.2¢ | $4.10 | $49.93 |
| West Virginia | 15.2¢ | $4.10 | $49.93 |
| Florida | 15.1¢ | $4.08 | $49.60 |
| New Mexico | 14.8¢ | $4.00 | $48.62 |
| Texas | 14.8¢ | $4.00 | $48.62 |
| Arizona | 14.7¢ | $3.97 | $48.29 |
| South Carolina | 14.7¢ | $3.97 | $48.29 |
| Kansas | 14.6¢ | $3.94 | $47.96 |
| Georgia | 14.2¢ | $3.83 | $46.65 |
| Iowa | 14.1¢ | $3.81 | $46.32 |
| North Carolina | 13.9¢ | $3.75 | $45.66 |
| Missouri | 13.6¢ | $3.67 | $44.68 |
| Oregon | 13.4¢ | $3.62 | $44.02 |
| Tennessee | 13.3¢ | $3.59 | $43.69 |
| Kentucky | 13.2¢ | $3.56 | $43.36 |
| Mississippi | 13.1¢ | $3.54 | $43.03 |
| Oklahoma | 13.1¢ | $3.54 | $43.03 |
| South Dakota | 12.7¢ | $3.43 | $41.72 |
| Montana | 12.4¢ | $3.35 | $40.73 |
| Nebraska | 12.2¢ | $3.29 | $40.08 |
| Arkansas | 12.1¢ | $3.27 | $39.75 |
| Washington | 12.1¢ | $3.27 | $39.75 |
| Louisiana | 11.9¢ | $3.21 | $39.09 |
| Wyoming | 11.6¢ | $3.13 | $38.11 |
| North Dakota | 11.5¢ | $3.11 | $37.78 |
| Utah | 11.4¢ | $3.08 | $37.45 |
| Idaho | 11.3¢ | $3.05 | $37.12 |
Efficient vs. inefficient
A $69.26/year difference across the wattage range.
Swapping a high-draw model for an efficient one pays for itself. Here's what that looks like annually at typical usage.
Most efficient
13000W
$3.22 per month
$39.15 per year
Typical
18000W
$4.46 per month
$54.20 per year
High draw
36000W
$8.91 per month
$108.41 per year
When it hits hardest
winter peak
Colder incoming water forces higher watts per gallon.
Ways to cut the cost
- 1
Flush annually to prevent scale buildup — scale kills tankless efficiency fast
Maintains 15-25% efficiency over time
- 2
Lower setpoint to 120°F
Saves 10-20% vs higher setpoints
- 3
Use low-flow fixtures — undersize a tankless and you'll run cold
Prevents running tankless at max watts
Real-world wattages
Pulled from actual spec sheets.
| Brand | Model | Watts |
|---|---|---|
| Stiebel Eltron | Tempra 24 Plus | 24000W |
| EcoSmart | ECO 27 | 27000W |
| Rheem | RTEX-18 | 18000W |
Picks that actually move the needle
Three products worth comparing if you're thinking about upgrading or supplementing what you have.
Some links below are affiliate links. If you buy, we may earn a small commission — it never changes the price you pay, and we only recommend picks we would stand behind.
See also
Related appliances
Sources: www.energystar.gov · www.energy.gov
Last updated: 2026-04-13