[petre]

We don't run an instant water heater. It's all gas or electric boilers.

For the stove I wired one phase to all the burners and the oven. It had one, two or three phase options. They're on a separate circuit with a 16 amp fuse. It's 2200W I believe. The breaker has never tripped.

400V is just not very common for residential in the Eastern Europe, maybe in your country you have instant electric heaters and other powerful appliances. My dad has recently upgraded his house to 400V 3 phase though, although he didn't need it but it's nice to have.