AFAIK the PoCos want their cheap rate electricity only to be used for defined appliances.
Usually that's night storage heating and hot water heaters here. At night the relay closes a big contactor, the storage heaters and boiler start charging. In the morning the control shuts off again and that has to be enough for the day. Some night storage heaters offer day-tariff auxiliary heating too, but generally it just gets cold in the evening. One more reason why I hate night storage heating, aside of the huge, ugly bulky heaters and the cost. Gas and oil are just a lot cheaper than electricity here.
