How does an electric water heater work?

A water heater is the appliance responsible for producing hot water in your home using an energy source, such as electricity.

There are various models, brands, and tank sizes, but the basic function is the same. Water heating accounts for nearly 20% of a household’s energy use in most homes.

When you use hot water — for example, to shower or wash your hands — it’s drawn from the top of the tank. As hot water leaves the tank, it’s replaced by cold water from the municipal water supply, which flows into the bottom of the tank. A lower heating element then heats this incoming water.

The water temperature inside the tank is maintained by two built-in thermostats (one at the top, one at the bottom) and the tank’s insulation, which helps retain heat for several hours.

To help prevent the growth of Legionella bacteria, the National Plumbing Code requires the water to be kept at a minimum of 60°C. The water in the tank is kept at this temperature — except in the small zone below the lower heating element, where the water remains warm but not hot (alt : lukewarm). Over time, this area could become more prone to bacterial growth if not properly managed.