How much electricity does a water heater use?
A standard 50-gallon electric water heater uses about 3,570 kWh a year - roughly $650 at the US average tariff. A heat pump water heater doing the same job uses 902 kWh, about $165.
Neither number comes from multiplying watts by hours, and that is the point. Every page answering this question does exactly that - 4,000 watts for three hours, 4,500 for two - and their answers disagree by a factor of eight because the hours are invented. The rating is built on something published instead: a fixed amount of hot water per day, heated through a fixed temperature rise.
- How much electricity does a water heater use per year?
- 3,570 kWh a year. That is a rating figure: it assumes a set amount of use rather than measuring yours. At 30¢ per kWh that is about $1071 a year.
- How much electricity does a water heater use per month?
- About 298 kWh a month, which is the yearly figure divided by twelve. There is no separate monthly measurement: the certification tests a year of defined use.
- How much electricity does a water heater use per day?
- About 9.78 kWh a day, the yearly figure spread over 365 days. It is not the nameplate wattage multiplied by 24: an appliance certified this way draws its rated power only part of the time, and multiplying by 24 hours overstates the real figure several times over.
Work it out with your own tariff
Residential sector, US average, as published in Electric Power Monthly released 26 August 2026. This is a revenue-weighted average across all residential customers and utilities, not a tariff any single household pays. In the same month the state residential averages (table 5.6.A) ran from 14.37 cents in Idaho to 52.72 in Hawaii, with California at 34.74 and New York at 29.49 — a spread of more than three and a half times. Use the figure from your own bill; the default here is a placeholder, not an answer.
Your rate, cents per kWh
There is no hours setting here, unlike the other device pages. This appliance is not certified in watts at all — only as a yearly total, and that total already includes a defined pattern of use. Multiplying it by hours of your own would count the usage twice.
| Period | Cost | Where it comes from |
|---|---|---|
| A year | $1,071 | 3570 kWh — the measured figure |
| A month | $89 | a twelfth of the year |
| A day | $2.93 | a 365th of the year |
3570 kWh × 30¢ = $1,071 a year. That averages 408 W drawn continuously.
3,570 kWh a year is calculated, not taken from a per-model label: standard electric resistance heaters are not ENERGY STAR certified and no open dataset publishes their annual use. It is 55 gallons a day heated from 58 \u00b0F to 125 \u00b0F - the medium draw pattern of the federal test procedure - divided by the minimum efficiency the same rules require of a 50-gallon electric tank (0.92). The arithmetic reproduces the certified annual figure of 599 heat pump water heaters with a median gap of 1.2%. Rate defaults to 18.34¢ (U.S. Energy Information Administration, June 2026) — a national average, which is wrong for you specifically, so put your own in above.
The wattage on the tank does not tell you the cost
Every page answering this question multiplies watts by hours: 4,000 watts for three hours a day, 4,500 for two, "9 to 15 kWh a day". The figures disagree by a factor of eight, and they disagree because the hours are invented - nobody measures how long your elements actually run.
They also answer the wrong question. Swap a 4,500-watt element for a 5,500-watt one in the same tank and the yearly bill does not change. Heating a given volume of water by a given number of degrees takes a fixed amount of energy; the element's power decides how fast that happens, not how much it costs. This is the same arithmetic as an electric kettle, where the energy to boil a litre is fixed and a 3,000-watt kettle simply gets there sooner.
What does decide the figure is how much hot water leaves the tank.
The federal test fixes exactly that, and publishes the number
The test procedure every water heater is rated under sets the water temperatures and the daily draw:
- supply water held at 58 °F;
- water delivered at 125 °F;
- a fixed schedule of draws totalling one of four daily volumes.
| Draw pattern | Hot water a day | Applies to a tank whose first-hour rating is |
|---|---|---|
| Very-Small | 10 gallons | under 18 gallons |
| Low | 38 gallons | 18 to 51 gallons |
| Medium | 55 gallons | 51 to 75 gallons |
| High | 84 gallons | 75 gallons and over |
Note what selects the pattern: the tank's own first-hour rating, not your household. A family of five and a single person with the same 50-gallon heater are both rated at 55 gallons a day. The label is a property of the appliance, not of you.
The arithmetic, in full
Heating 55 gallons from 58 °F to 125 °F:
55 gal × 8.33 lb/gal × 67 °F = 30,697 BTU a day ÷ 3,412 BTU per kWh = 9.0 kWh a day × 365 = 3,284 kWh a year, delivered into the water
That is the floor. No heater can put 55 gallons a day through that temperature rise for less. What it actually draws from the wall is that figure divided by the unit's uniform energy factor.
Does this arithmetic match reality? It reproduces the certified annual figure for 599 ENERGY STAR heat pump water heaters with a median gap of 1.2%, and within 5% for 83% of them. The remaining gap is mostly the efficiency being published to two decimal places. Treat the number as good to a couple of percent, not to the kilowatt-hour.
So: a standard electric tank
The federal minimum for an electric storage heater of 20 to 55 gallons on the medium pattern is an efficiency of 0.9307 − 0.0002 × the rated gallons - 0.92 for a 50-gallon tank.
3,284 ÷ 0.92 = about 3,570 kWh a year
At the US average tariff that is roughly $650 a year, which is why water heating shows up as one of the largest single items on an electricity bill.
A heat pump does the same job for a quarter of it
| Median | Middle half | Models | |
|---|---|---|---|
| Low draw, 38 gal/day | 780 kWh | 724-780 | 16 |
| Medium draw, 55 gal/day | 902 kWh | 855-923 | 272 |
| High draw, 84 gal/day | 1,279 kWh | 1,230-1,381 | 311 |
Certified heat pump water heaters, measured under the same test. The median efficiency is 3.68 against 0.92 for resistance: a heat pump moves heat rather than making it, so it can deliver more energy into the water than it draws from the wall.
At 902 kWh that is about $165 a year.
The resistance tank above costs $650 for the same hot water, measured the same way.
Above 55 gallons, a plain electric tank no longer exists
This is the part worth knowing before you shop. The minimum efficiency for an electric storage heater over 55 gallons is 2.1171 − 0.0011 × the rated gallons - that is 2.03 for an 80-gallon tank.
An efficiency above 1 means delivering more heat than the electricity you consumed. A resistance element cannot do that, at any price, ever. So the rule does not merely make large resistance tanks inefficient; it makes them impossible to certify.
If you are replacing an old 80-gallon electric tank and cannot find one, that is why. What is sold in that size is a heat pump.
Per month, and why yours will differ
3,570 kWh over twelve months is about 298 kWh a month, roughly $55. But the whole figure rests on 55 gallons a day, and that is the one number in the calculation that is about you rather than the appliance. Two people who shower briefly will use less; a household running a bath and a dishwasher daily will use more, and the cost moves with it almost exactly in proportion.
That is the honest version of "it depends" - the dependency has a name, a unit, and a published default.
What it costs you specifically
Set your own tariff below.
What this does not account for
The daily draw is the assumption that matters. 55 gallons a day is what the test uses for a mid-size tank. Your household is not that number, and the annual figure moves in proportion to it: half the hot water, roughly half the cost.
This is a calculated figure, not a per-model published one. Standard electric resistance heaters are not ENERGY STAR certified, so there is no open dataset of their annual use. The 3,570 kWh here is computed from the published test conditions and the federal minimum efficiency, and it is checked against 599 certified heat pump models where both the inputs and the answer are published. A specific model's EnergyGuide label may differ by a few percent.
Inlet temperature is a real variable and it is not in this figure. The test holds supply water at 58 °F. A northern basement in February is colder than that and the same shower costs more; a warm climate is the reverse. This is the largest single reason a real bill differs from the label.
Gas water heaters are not covered here. They are rated on the same draw patterns but consume therms rather than kilowatt-hours, and their electricity use is limited to controls and, on some models, a blower.
Heat pump figures assume the heat pump is running. Hybrid units fall back to resistance elements in cold air or under heavy demand, and in that mode they use resistance-level energy. The certified figure is measured at defined ambient conditions.
Worth reading next
Sources
- 01ENERGY STAR certified heat pump water heaters — certified annual electricity useU.S. Environmental Protection Agency ·
- 02Electric Power Monthly, Table 5.3 — average price of electricity to ultimate customersU.S. Energy Information Administration ·
How these figures are produced: see our methodology.
Figures are calculated from published wattages and a published tariff, both dated above. They are good for comparing devices, not for predicting your bill: your rate, settings and usage all differ.