Electric water heaters operate by resistance elements within the water containment tank. These units can be equipped with either one or two elements. Models with two elements usually have one located in the upper portion and one in the lower portion. Each element has an individual thermostat control found behind the access plates.

As previously described, hot water is drawn from the top of the tank and replaced by cold water entering at the bottom through a tube.

When the demand for hot water is low, the lower heating element operates to maintain the water temperature. As hot water demand increases, the upper heating element comes on to maintain the water temperature. Hot water is drawn from the top of the tank. the top element turns off, and the lower element comes back on to maintain the set temperature.