> A tankless electric water heater could use that much I suppose. I wonder if that is what Germany uses? Tanks take up more space, but they need a lot less power at once so they are kinder to the grid.

Tankless water heaters are much more common in rental apartments, and Germany has one of the highest quote of people living in rented apartments. And if space is at a premium, of course tankless heaters are preferable. Apartments are also the reason why electric stoves (again, using 400V tri-phase) are so popular in Germany.