Photovoltaic system at the multi-family house. 100% approval from the homeowners' association?

This topic is really a point of contention, I see. It could cause major disputes within the community of owners....

Certainly. One will probably only be able to say more about some details after one or another court ruling. However, the law aims to facilitate such investments.

I find this an interesting question. How does it work in a building with 4 units, assuming the photovoltaic system came about?

In addition to the methods mentioned by , there is also the possibility, within the framework of §22 para. 5 WEG ("The condominium owners can decide on a different distribution of costs and benefits. By such a decision, no costs may be imposed on a condominium owner who is not required to bear costs under the preceding paragraphs."), to agree on a method to operate the system (financially) sensibly and "fairly."

Yes, if the roof is, for example, black or dark, it does not stand out. But if the roof - as usual - consists of red tiles, it stands out a lot! Cooler on the roof is nonsense. Modern roofs are well insulated. If anything, the roof sweats when there is no good air circulation under the photovoltaic system. So not only “advantages.” This topic is more than hot when several owners are involved. If everyone agrees, then all is ok. But if the majority is barely reached, and the “losers” have to pay for it (photovoltaic under a children's room, bedroom, for example, need little electricity, etc.), there will certainly be big problems. In new buildings, every owner knows what they are getting into. But in renovations, not. And whether such a system really “pays off in time” is also a question. Not all owners want to constantly invest...

If the roof, however - as usual - consists of red tiles,

Why is red normal? Nowadays black is normal. Clay roof tiles were classically untreated red in the past. But that was a long time ago.

Cooler on the roof is nonsense. Modern roofs are well insulated.

It is actually true that photovoltaics lower the temperatures on the roof.

If at all, the roof sweats when there is no good air circulation under the photovoltaics.

That is nonsense now ;)

This topic is more than hot when several owners are involved.

No one disputes that. But it is much easier to decide on photovoltaics than to prevent it.

But if the majority is barely reached, and the "losers" have to bear the consequences (photovoltaics under children’s rooms, bedrooms, for example, need little electricity, etc.), there will certainly be big problems.

Then the photovoltaic system in the community is the lesser problem if the community is that divided. In my opinion, that always degenerates into petty conflicts and often ends in people moving out. Aside from that, with such a tight vote, co-owners who do not want the system do not have to pay for it either (see our contributions on this). This ensures that the system can be installed on the roof in any case, but no one is forced to pay for it.

With new buildings, every owner knows where they stand. But with renovations, they don’t.

Yes, because the renovation is decided by the community and everyone knows what is being voted on. It is nothing different than a new building.

And whether such a system really "pays off in time" is also a question.

A multi-family house is usually a larger object. That makes a larger system possible. That lowers the prices. That means the system always pays off very early. I (and I speak from experience as a landlord of various apartments) would only want to implement extensive measures in one of my condominium associations with broad approval. Anything else only leads to stress.

That's exactly the problem.
Don't create stress!
That's probably why first getting an offer to see when the system "pays for itself."
For some, that's already an argument.
And then, where it will be installed.
The roof doesn't look nice after that.
It's a matter of taste...
And whether the funding will improve after the election must also be considered.

The roof doesn't look nice anymore then. It's a matter of taste...

Everyone probably feels differently about that. I associate a roof completely covered with photovoltaics with modern technology and clean energy, which I also find nice. But I also like wind farms in the landscape, which strangely are often vilified by others...

Yes, if the whole roof is nicely covered with it maybe. But if it's a mishmash with solar collectors, photovoltaic elements, and sometimes nothing in between... It then looks rather patched together. Definitely not a new building... In such a case, one probably has to offer something to the owner who is against it. A compromise, basically.