Night Storage Heating are insulated boxes containing bricks with electrical elements running between them. When the electricity is switched on, the bricks heat up. This is called ‘charging’ the heater.
The storage bricks are covered with insulation. This holds most of the heat in the box for up to 14 hours or so but this heat will eventually ‘leak’ out.
At the top of the box is a flap, which can be opened to let the heat out more quickly.
The objective of night storage heating is to utilize the cheaper electricity available during the night.