You mean, like air conditioners that freeze water into ice overnight and then use that as the heat pump sink during the day to shift AC demand from peak to off-peak.

Of course, you pluck the lowest hanging fruit first ~ first you convert from stand up to drawer freezer/fridge. Once you have that, though, time-shifting operation ~ taking it to a lower temperature at off-peak than on-peak periods, doing ice cube making off peak, etc ~ that's the obvious next step.

As far as cost, its already controlled by an electronic controller, powered from the mains power ~ taking the signal off the mains power and feeding it as data into the control board might add a few Euro to the cost, but its mostly programming.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.