Well, when I look at your contract terms, everything is excluded except for a wood-burning stove that you are allowed to operate as a secondary energy source (you could clarify, for example, to what extent it may be a water-based one with which you can heat the domestic water tank, or just do it ) Everything else, if I read it correctly, will not be allowed... Moreover, it wouldn’t make sense anyway since you would be buying a double heating system that would also have to be integrated into the heating system, which they will not tolerate; although you wouldn’t be working in their heating circuit because it usually only consists of heat exchangers with two separate circuits between theirs and your water circuit, it would still have to be properly integrated by the heating technician, and normally only their installer is allowed to do that. I would, because it can’t be helped, accept it like that and just put a regular wood-burning stove in the place, which I would have installed anyway; at least that doesn’t cost as much as a water-based one.