Hihi, that's more questions than I thought of myself while I was thinking about what the follow-up article about the electrical appliances might look like... Well, I don't have time for that at the moment anyway: too many comments to answer... ;-))

The system is ‘off grid’, there is a socket in the basement that has its own fuse and is supplied with power when the rest of the country is in the dark... ;-)
However, I have switched off the 40% battery reserve, which was set as fixed for emergencies, for the time being. I don't believe in the big blackout. We used to get candles out of the drawer when the power went out...

We have a 5 kW battery. We'll see if it's enough first. Such deals (buy cheap electricity, sell expensive) are not possible in Germany at the moment. The selling price is far below the cheapest purchase price (which is monitored by the state).

Yes, we have to register (which has already been done). However, with a system under 30 kWp you do not have to pay taxes as a ‘businessman’. Here you have to register any system over 500 Wp if you feed electricity into the socket.

The ‘tool shed’ doesn't even have lighting... But I'm working on it and will wish for a huge mobile battery for Christmas... ;-)))