Electrical storage heaters or radiators come in a variety of different designs, with some using water, heat-retentive bricks or under-floor concrete. To run a storage heater cost-effectively you should be on an electricity rate plan that charges a lower rate at night.
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Heat Storage - Storage heaters use electricity to heat a heat-retentive unit such as insulated bricks or a large tank of water. They store the heat during the night, when electricity is cheaper, and release it during the day when the heat is needed.
Releasing Heat - The amount of heat released during the day can be controlled either manually or automatically. In automatic models the heater senses the temperature of the room and releases heat accordingly. In water storage heaters the hot water can be run through the normal central heating radiators. Units that use bricks tend to be separate appliances.
Uses - Storage heaters tend to be used to prevent the house from becoming below freezing in winter or in infrequently-used rooms. For normal day-to-day winter living, you may still need a conventional electric heater to keep rooms comfortable.