>Air conditioners could do it too, right?
Some heat pumps do this. E.g. Panasonic Aquarea EcoFleX. When cooling the house, the domestic hot water tank is used to dump heat into (up to a certain temperature).
Some heat pumps do this. E.g. Panasonic Aquarea EcoFleX. When cooling the house, the domestic hot water tank is used to dump heat into (up to a certain temperature).