It appears to me that in France, the heating of most domestic hot water is done in a hot-water tank, using off-peak electricity. We have one such in our house, a fairly new one, since the old one was getting past it, and was scruffy into the bargain. This new heater heats the water to about 65 degrees, and you can't adjust the temperature. It's a treatment against legionella, a rather nasty bacterium that dies at temperatures over 60.
Water expands when it is heated (one of the reasons that sea levels are rising) and water sanitation authorities get worried by the possibility that heated water gets into the drinking water pipes. I'm not sure why this is a concern, it might be a legionella thing again, but in any case to prevent this from happening, the cold water inlet to the heater must be fitted with a non-return valve. And the trouble with this is that if the expanding water can't escape, the pressure builds up until something bursts, so the tank has also to be fitted with a pressure-release valve, and a water trap connected to your waste water disposal pipes. Here is a picture of my water heater with the gubbins fitted. The heater is mounted on what the French insist is a tripod (trépied) even though it has four legs.
As an alternative, you could connect in an expansion vessel that keeps a near-constant water pressure as the water expands. The people who sell these they tell you that the traditional system wastes up to 200 litres of water a year. Doesn't sound very much to me, and it wouldn't cost much either, unless you've heated it, and the system is designed to only waste the cold (or perhaps lukewarm) water.
Anita doesn't like water coming out of the taps at 65°C. It's too hot to keep your hand in. So today I fitted a temperature regulator that mixes cold water in with the outgoing hot, to cool it. Seems to work so far. We will see tomorrow what it does to the shower, or shaving water temperature.