> In theory you could build them to be safe, but often they aren't. I showered with a tank-based electric shower today: you fill the tank, plug it in until it's hot, unplug it, step underneath, and open the valve.
Do any homes have things set up like most homes in the United States - that is, a central water heater of 40 gallons or more that supplies all taps in the house?
Something else we have here, but aren't as common, are "instant on" heaters; they come in two fashions:
1) Tankless - basically similar to the "electric showerhead", except much higher wattage and installed usually below the sink for both sink and shower usage (if in a bathroom). Water flows in and thru a very tiny holding tank, is rapidly heated, then passed to the tap.
2) Recirculation - in this system, the hot water side of things is basically connected in a loop fashion to the main water heater, and is circulated with a pump. The main water heater, IIRC, can also be smaller. The lines are also all insulated. Hot water is circulated around, turn it on, there it is.
In the usual system, though, you turn on a tap and wait for it to "warm up"; our American wastefulness in action I guess (but technically, at least in most non-rural areas, that water goes down the drain and into the sewer system, where it is taken back to the water purification plant, and is essentially turned back into drinking water - while it doesn't all return, due to evaporation, leaks, etc - the majority I would surmise does, so while still wasteful, it isn't as terrible as you might imagine - but you do still have to pay for that extra water, which is where it does hit ya).