My brand new (last year, anyway) high efficiency water heater is direct wired. The plumbers connected it. I can't say I've ever seen a plug-in water heater (bigger than a few gallons).
What does this mean? Literally replacing all the overhead lights with a ceiling fan w/light attached?
All the overhead lights outside of the kitchen and showers were cheap "boob lights." The kitchen and shower lights are LED pucks that mount flush to a shallow box and kind of look like recessed lights. First we replaced all of the boob lights with wider LED panel lights with a warm color temperature. While doing this I noticed something about the light boxes in the centers of the living room and bedrooms: the boxes were mounted so they are centered over a joist, meaning you can screw a fan directly into the joist. They also had two hot conductors running from the switch box. One was colored red and the other was colored black. The red one was wired from the switch to the light, and the black one was capped at both ends. They were set up to have fans installed without any modification to the box.
https://en.wikipedia.org/wiki/Split-phase_electric_power
Three phase circuits are 120 degrees out of phase.
But completely agreed that three phase 400V seems crazy!
Ok, help from our new common friend:
Yes, your statement is essentially correct. In the United States, residential electrical supply is typically a single-phase, 240-volt system that is "split" into two 120-volt legs. Each of these legs are 180 degrees out of phase with each other, which allows for both 120-volt and 240-volt circuits within the home. This arrangement is often referred to as "split-phase" electricity. It's not technically two-phase because a true two-phase system would have two waves offset by 90 degrees, not 180.
In the US houses get 1 of the 3 phases. That phase is split in half, and so each phase is 180 degrees. This is different from 3 phase power where each phase is 120 degrees. 3 phase is good for a few things, but for a water heater it doesn't matter, and most of the things 3 phase is good for you today will run off of an inverter for speed control which in turn can run off of single phase (3 phase is still better but only because you can use smaller capacitors)
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.
More capable options exist if needed, but I have never seen them in a residential setting.
[0] The 30 indicates that it supports a peak wattage of 30.
The kitchen and laundry appliances are sometimes moved with the homeowner or tenant, but not the water heater. Also a plug can make it easier to pull out for cleaning.
On the upside, even a small studio apartment usually has enough space and an extra water hookup for at least a washing machine, so no dealing with other apartment residents or a public laundromat for laundry. Dryers are usually condensing; no need for an outside vent.
Until the last few years, short tenancies were unusual for Germans; in the little building we rented in before we bought our house, the other tenants had been renting there for 20-40 years! Given the terms of our contract, I gathered that they must have had very small, if any, rent increases written into their unrestricted contracts, and the only way to get them out was if the building owner decided to live in one of the units herself.
But I'll grant that appliances are probably moved more often than water heaters are.