Photovoltaic system: Costs, saving potential? - Experiences?

That is exactly why I wrote "building law-related". I would now guess that the development plan is 30 years old; back then, photovoltaic modules on the roof were about as popular as satellite antennas on the balcony of a rental apartment. Nowadays, (also due to the further development of module aesthetics) you really can’t seriously score points with design appeal anymore, and the regulatory authority is likely to see it that way too. And we haven’t even touched on the current energy/climate discussion yet.

Unless we are talking about a building gap between listed half-timbered houses, I wouldn’t have a crippled, expensive botched system installed for that reason, but rather drop by the office very politely.