Connect WW treatment to existing heating

Boiler is not the same as a tankless water heater.

When renting out an apartment, remember that the tenant either needs their own heating or, if it is central, heat meters are necessary. Allocation of heating costs purely based on living area, housing units, etc. is not acceptable.

I can only agree with Alex85 on that. You need the heat meters for the heating.

And I also find warm water from a properly dimensioned central heating system much more practical for the kitchen than a boiler / instantaneous water heater.

Thank you up to this point!

I will discuss this with the installer and I also need to see where I will install the heat meter for the rental apartment. Because the central heating is basically "one" for both living areas, so not separated. The current tenant hasn't been interested in this for 30 years; she is moving out now anyway, as we are renovating.

All costs should/must then be separated: water, electricity, heating.

Boiler is not the same as a tankless water heater.

Strictly speaking, yes (and I should be the least likely to "complain," since I myself pay attention to the difference between knee wall and dwarf wall), but here I really meant a boiler that we had above the sink. However, in "common parlance," I have indeed heard "boiler" used for both. All the more reason, I suppose, to point out the difference.