Hot fill washing machines/dishwashers?

[ace llani]

Back in the good old days, I remember there being a hot and cold water supply on some appliances.

Given the cost of electricity, and as my appliances are right next to the kitchen sink( so could run the hot tap) - could I just connect to the hot water?
We don't have the temperature up very high on the water, and it's a pretty new boiler.

Wondered if the cold inlet could handle "hot" water, and does the appliance work on internal water temp or a given time that the appliance should take to get up to temperature.

[Mussels]

I want to champion these but I suspect there's so little benefit I don't see the point.
A dual fill machine would need to reliably take hot and cold at the same time and end up with a tankful at precisely the right temperature. Apart from the extra purchase price there are several more bits to go wrong, how much would it save me when I mostly do 30 degree washes?

[Cousin Jack]

It was a long time ago that machines had hot and cold fill, 25 years at a guess. 10 years ago we moved house, and in the old house I had capped off the HW supply before buying a new wahing machine. That nw macine was about 15 years old when we moved ou