How Much Electricity Does a Water Heater Use?
So how much electricity does a water heater use? A standard 40-gallon electric resistance water heater has heating elements rated at 4,500 to 5,500 watts, though only one element runs at a time in normal operation. Because it's one of the highest-wattage appliances in a home and runs whenever hot water is used up, it's typically one of the larger contributors to an electric bill — use the calculator below with your own rate for a real estimate.
Calculate your cost to run a water heater
Enter your rate to see your estimate.
What affects how much electricity a water heater uses
Tank size is a major factor: a larger tank holds more water to heat and reheat. Most residential tanks have two heating elements, but only one runs at a time in normal operation, cycling on when the thermostat senses the water has cooled below its set point. How much hot water your household uses, and the thermostat's temperature setting, both directly affect how often and how long the elements run. Tankless (on-demand) electric water heaters work differently, heating water only as it flows, but typically require a much higher instantaneous wattage while running.
How to reduce your water heater's electricity use
- Lower the thermostat to 120°F, which is hot enough for most households and reduces standby heat loss
- Insulate the tank and the first few feet of hot water pipe if the tank feels warm to the touch
- Fix dripping hot water faucets promptly, since every drip is water the heater has to reheat
- Spread out high hot-water-use activities (showers, laundry, dishwasher) rather than running them back-to-back
Typical wattage figure: 4,500-5,500 W (40-gallon electric resistance tank). Source: DOE-developed appliance energy table, reproduced by Virginia Cooperative Extension (Virginia Tech), publication BSE-301. Most residential tanks have two heating elements but only one runs at a time in normal operation. We review this figure periodically and update it if the source changes; last checked September 2026.
Frequently asked questions
How many watts does a water heater use?
A standard 40-gallon electric resistance water heater has elements rated at 4,500 to 5,500 watts, according to a DOE-developed appliance energy table reproduced by Virginia Cooperative Extension, though only one element runs at a time.
How much does it cost to run a water heater?
A 4,500-watt water heater running an estimated 3 effective hours a day at the U.S. average rate of about 16.5 cents/kWh costs roughly $2.23 a day, or about $67 a month. Use the calculator above with your own household's usage and rate for a more tailored estimate.
Why does my water heater seem to run so much?
It's reheating water every time hot water is drawn from the tank, plus it periodically cycles on just to offset standby heat loss even when nobody's using hot water, especially on an uninsulated tank. Higher household hot water use and a higher thermostat setting both mean more total runtime.
How can I reduce how much electricity my water heater uses?
Lower the thermostat to around 120°F, insulate the tank and exposed hot water pipes if they feel warm, and fix any dripping hot water faucets, since every drip is water the heater ends up reheating.
This page provides estimates based on typical wattage figures and the numbers you enter, using an estimated 'effective hours' figure to represent cycling rather than continuous running. Actual electricity cost depends on your specific tank size, thermostat setting, and household hot water use.