There is no concept of "Warmmiete" in NLD as far as I know. When you rent an apartment, you simply arrange your own water/gas/electricity/Internet connections yourself. And when you leave the rented place, you simply stop the contracts (or notify them of a move elsewhere) and the next renter chooses their own providers again. In turn, the energy provider has always a direct relationship to the person/family/entity who lives in the dwelling. Of course there may be some exceptions, but I never heard of them. This is how it works "normally".
@FailForward @isotopp That explains it. Long story short: The NL compensation model doesn’t work in DE.