Single-family house photovoltaic system with 30KW

I would be interested to know how one can prove that these do not belong to the spouses jointly but separately.

It’s quite simple: The system must be registered with the grid operator by the operator. This documents who the operator is. The operator is also clearly identified in the MaStR.

Thank you very much for your answers. I have decided to install 25kWp initially. Can you say something about the inverters and battery storage? Huawei SUN 2000-17K-MB0 => 25.5 kWp inverter => approx. 2000 € Huawei LUNA2000-15-S0 => 15 kW battery storage => approx. 5520 € Possibly an alternative?

For the precise dimensioning of the components, I can highly recommend Photovoltaik-SOL as a 30-day demo version. This allows for excellent simulation of photovoltaic modules (orientation, tilt, arrangement, strings), inverters, and storage.