How Much Does It Cost to Run an Electric Water Heater?

A household using about 60 gallons of hot water a day uses roughly 400 kWh a month, around $70 at the national average rate and well over $100 in the Northeast or California. A single person uses a third to half of that.

Yes, through standby loss. The tank cools slowly and the element runs briefly to make up the difference, typically 1 to 3 kWh a day depending on the tank's insulation and the temperature of the room it sits in.

Yes. Scale builds up on the heating element and tank bottom, insulating the element from the water, so it runs longer to deliver the same heat. The effect grows with hardness and tank age, and the scaled element usually fails early.

In most climates and especially at electricity rates above 15 cents per kWh, yes. It uses about one third the electricity of a resistance tank. It needs a space with some air volume, such as a basement or garage, and it cools and dehumidifies that space a little while it runs.

A standard 50 gallon electric tank draws 4,500 W whenever it heats. It has two 4,500 W elements but only one runs at a time, on a 240 V circuit, which is about 19 amps (4,500 / 240 = 18.75 A).

About $2.34 a day for a household using around 60 gallons of hot water: 4,500 W x 3 hours = 13.5 kWh, and 13.5 x $0.173 = $2.34. Over a year that is about 4,930 kWh, or roughly $850 at the national average rate.

Yes. The DOE puts water heating at about 18 percent of a typical home's energy use, and in an all-electric home the tank is often the largest load after heating and cooling. A family of four can easily use 400 kWh a month on hot water alone.

Only a generator with 240 V output and at least 4,500 W to spare, connected through a transfer switch or interlock. A portable power station cannot run one. Most people leave the water heater off the backup circuit, since a well insulated tank keeps water warm for a day or more without power.

Somewhat, because it removes standby loss, typically 1 to 3 kWh a day on a tank, which is about $63 to $190 a year at 17.3 cents per kWh (365 x 1 to 3 kWh x $0.173). The energy to heat the water you actually use is the same, and a whole-house tankless unit needs a very large electrical service. A heat pump water heater saves far more.

Yes. The DOE estimates that each 10 degree reduction in tank temperature saves about 3 to 5 percent on water heating costs, and 120 degrees is enough for most homes. On a $70 a month water heating bill, dropping from 140 to 120 saves roughly $4 to $7 a month.