[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.