How Do Night Storage Heaters Work?

Purpose

In general, electric utilities charge different rates at different times of the day. During peak hours when a lot of people are using their electricity, utilities will increase the price to reduce demand on the system. During off-peak hours, such as in the middle of the night when fewer people are using electricity, the utilities will lower the prices. Night storage heaters are designed to take advantage of this pricing structure. They use electricity to generate heat at night, when it is cheaper, then use that same heat during the day to heat the house.

Night storage heaters are powered by electrical heating elements much like those used to power electric ovens and stoves. These heating elements are resistors--materials that resist the flow of electric current. When electricity flows through these elements, it is turned into heat. In a night storage heater, the elements are located adjacent to bricks. The entire heater is insulated and controlled by a thermostat with a timer.

Sometime in the middle of the night, a timer automatically turns on the thermostat. The thermostat sends electricity into the heating elements, which heat the bricks. The thermostat continues to heat the bricks until they have reached the desired temperature, then turns off. The insulation prevents most of the heat from leaking back out, but some of it does nonetheless.

Most night storage heaters are designed to heat a single room. A flap opens in the side of the heater, allowing hot air to flow out into the room. The thermostat controls the flat, opening it just enough to heat the room to the desired temperature. As the day goes on, the night storage heater may run out of heat. If it does, the homeowners may use a back-up system to provide additional heating.