by the way Rossi's remark that the device can only do house heating, is not so true. with hot water storage like we have for electric water heater, heating 150litter at 60C when electricity is at night price, it could be simple to use e-cat, and even more easy, because you don't have to wait for night to reheat water.
you can do the same for house heating, either with (very) hot water, or like it is done today with very heavy radiators that you charge long, then let warm the room. they are expensive but sold as electric heater to save cash by using night electricity
