Photovoltaics - Questions about Tax/Business

I already have an offer. 11T for 8.58 (26 panels). East/South roof 24 degrees. What do the panels weigh per m2? Do you know that? The structural engineer said I can load the roof up to 15kg/m2

Check the datasheet of a current panel. They are all similarly constructed and weigh about the same. IIRC around 20kg for 1x1.6m². Then add the substructure. That will be tight. Does your roof have so little reserve? The snow load, which will of course still be added, is significantly more.

In my opinion, a storage system is only worthwhile below 600€/kW capacity, and current storage systems are still well above that. That's why we don't have a storage system and will upgrade it sometime when the costs for storage have decreased.

That is a pretty good benchmark; I was actually thinking more in the range of around 500€. I myself always complained against storage systems and now have bought one myself. However, only because the risk with an investment of 4,400€ for 11kWh remains manageable. 15kg is too little for the panel, substructure, and snow load. But it's so little again that I can hardly believe it.

no without snow load, that comes on top again. And I suspect the 15 kg source only meant the module, so also without substructure. It's more about if a photovoltaic module weighs e.g. 20 kg, how much snow load is then left on the roof...

calculate 10-12kg/m² for the modules. It will be a tight box. You must not forget that the modules, unlike snow, also have suction load due to wind. Both were planned by the solar installer in our case.

Well, according to the construction performance description, the roof structure has an allowable snow load of 100 kg/m² (1.0 kN/m²). Now the question is how much snow load buffer is still needed at a 25° slope when 20 kg of modules and substructure are additionally on it. Should I best mount a hand broom on a drone already?

That the surplus electricity from photovoltaic systems will be purchased is uncertain for 2021, if not unlikely. Is a photovoltaic system worthwhile even without feeding in the surplus electricity? And what about the storage? Our builder said that it is currently not worth it and one should wait 1-2 years.