Presumably they wouldn't care which appliance you attach? The same deal would make total sense with e.g a smart charger for an electric car (in fact anything el

Presumably they wouldn't care which appliance you attach? The same deal would make total sense with e.g a smart charger for an electric car (in fact anything else would be nuts) and probably anything else with a big enough battery. If the difference between the two rates you are charged is large enough it may even make sense to have a battery and switch between the cheap source and the normal one if the cheap one is cut of.