This HN thread is the first time I learned about 400 V to homes in Europe. My oven is 220 V. I just checked the manual. All my house is 220 V. I live in Italy.

Plugs are usually Shuko for high power appliances (washing machine) and two smaller pins for low power (phone chargers.)

By the way, Italy traditionally had a three pin in a line high power plug but more and more appliances are coming with Shuko plugs so wall socket are either bi-standard or just Shuko now.

The 400V is between phases. 230V is between a phase and ground. Ie, you get 3 wires (phases) of 230V from the 400V connection.

Btw, Europe standardized at 230/400V in the nineties. In Czechia we switched from 220V to 230V in 1993. Not sure when Italy did, but probably around the same time.

"Standardized". The allowable voltage for power is normally something like 6%. When they switched from the mis-mash of 220 and 240V to 230V, they specified the allowable voltage range was wide enough to encompass both of those, including the allowable voltage range for 240V. So largely it was just "Everything is 230V now, and try to make sure new stuff is actually 230V".

Yes. “Standardising” to 230V +/-10%, allows for 220/230/240V +/-6% (the previous standards used in different countries) to all coexist without actually changing any equipment.

My UPS most of the time reports just under 240v.