The static storage heaters release heat by natural convection in two different ways. There is a primary convection controlled by a top flap that releases hot air after the storage heater is charged. But there is also a natural secondary convection that releases hot air 24 hours a day. This natural secondary convection is generated by the design of the machine allowing a constant release of heat without leading to additional energy costs. Storage heater only consumes energy during off-peak hours at night.