European dishwashers seem to be designed vastly differently to American ones.

Water efficiency goals specifically; I've seen consumption of 7 US gallons (26.5 litres) per cycle called "eco" on American dishwashers, where mine (Miele) claims 12 litres on the heaviest cycle.

The manual for mine calls out connecting to hot water as a way to increase efficiency if you have hot water with a >1 COP, mentioning solar or heat pump cylinders.

A professional I asked noted though that for protein-heavy residues (like egg), hot water could bake it on before the dishwasher starts cleaning it.