[Scoundreller]

And 240V gives you a lot more power to heat water at point of use. You're not just heating the water, but several kg of ceramics inside.

But I still don't get it: as dishwashers are usually in the kitchen, isn't a hot water line just as far away as a cold water line?

Or is the concern that there are more "on-demand" hot water heaters and a simultaneous shower might max them out?

[OJFord]

I think it's: 1) might not be on-demand, so then your hot fill might not be hot at the right time; 2) if it is hot, it will almost certainly be <70C, which is typically the max cycle temp.. so you either can't have that or still need a local element to get it there; 3) even if it's hot enough, you also need cold fill, so you can mix and get the temperature(s) you need.

Frankly I think even with some assumptions about your market to ignore 1 & 2, 3 alone makes it more complex than just taking a cold fill and heating to temp within the dishwasher. I believe the very few models that do have a hot fill do it on an eco basis (you already have hot water use it here too) but the validity of that is disputed, and really the only obvious benefit is to the EPC sticker (characterising energy performance) which will appear best in class (the class of all dishwashers) just by not having a multiple kW heater, not accounting for that having been offloaded to the boiler.

[eru]

> Or is the concern that there are more "on-demand" hot water heaters and a simultaneous shower might max them out?

People might also have a hot water tank, but only turn on that heater when people want to take a hot shower.

[Scoundreller]

It doesn’t really work that way unless you take verrrry short showers or turn it on hours before you need it.

[eru]

How long is a short shower for you?

We turn our hot water tank on a few minutes before we want warm water for the shower. Most of the time we don't bother and shower cold, though.

[Scoundreller]

I’m probably incredulous because our tap water is 5-10C.

[eru]

Well, ours is about 25C.