How Much Does an Electric Water Heater Cost to Run?

Electric water heaters can be significant contributors to household electricity use because heating water requires substantial energy. The actual cost depends on heater power, how long the heating element operates, water temperature, incoming water temperature, household hot-water use, tank size, insulation, and electricity rates.

A simple example

Suppose a heating element is rated at 4,500 watts and operates for a total of two hours in a day.

4,500 watts ÷ 1,000 = 4.5 kW.

4.5 × 2 hours = 9 kWh per day.

At $0.16 per kWh, that would be about $1.44 per day, or roughly $43.20 over 30 days.

This is a simplified example. A thermostat normally switches the element on and off, so the element does not necessarily draw its full rated power for two uninterrupted hours.

What affects water-heater cost?

• Water temperature setting.
• Amount of hot water used.
• Incoming water temperature.
• Tank insulation and age.
• Pipe heat loss.
• Electricity rate.
• Heating element size.

Reducing unnecessary energy use

Follow the manufacturer’s recommendations for temperature and maintenance. Fix hot-water leaks, reduce unnecessary hot-water use, and make sure insulation and installation are appropriate. Never change electrical connections or safety components unless the work is performed by a qualified professional.

Use measured data when possible

If your heater is compatible with a suitable energy monitor, measured kWh over several days can provide a better estimate than assuming the heating element runs for a fixed number of hours. Any measurement method must be appropriate for the appliance’s electrical load and installed safely.

Calculate your estimate

For a basic estimate, enter the heater’s wattage and estimated operating hours into our Electricity Cost Calculator.

Bottom line

The rated wattage tells you how much power the heater draws while an element is operating; it does not by itself tell you the monthly bill. Runtime and actual hot-water demand are what turn power into energy consumption and cost.