[MarioMan]

That’s pretty wild, since the energy needed to get it up to temp would still need to be expended on the water heater side. There are no real energy efficiency gains unless they can somehow engineer an effective cold water cleaning.

[russdill]

Many hot water heaters use gas which may be cheaper than resistive heating depending on where you live. Additionally, there are now water heaters that use a heat pump which will be more efficient than either.

And of course they'll be setups that use solar heating or are programmed to heat by time of day.

This is all down in the weeds though because a dishwasher does not use very much water.