Photovoltaic system: Advantages and disadvantages, experiences, worthwhile?

Thanks first of all for the clarification. I had no idea that the batteries are so expensive. What capacity do you need for a single-family house with 150 sqm that makes these things so expensive? On the internet, I find lithium batteries ranging from... to... - at first glance, they don’t seem that much more expensive compared to the photovoltaic system. Unfortunately, we cannot rely on any own contribution for the photovoltaic system. In other words, a photovoltaic system with KFW funding: you can do it - battery: better to stay away? Actually, my primary concern is self-consumption; I didn’t know anything about taxes on feed-in until now - is it mandatory to feed in?

One must say, the hotter it is, the more inefficient the system becomes. I have read from many that the best month in 2018 was May. All other months, especially the weeks with 30 degrees, were worse on average.

My July was even better, although the diagram only shows the sold kWh... I always read from the bidirectional meter...

Photovoltaics in EL is of course cool, since the material basically costs nothing. But climbing around on the roof was still too risky for me... If you're doing it in EL anyway, why did you build it so "small"? What is that? 7 kWp? you don't have to feed in, but then it becomes a very expensive hobby. Taxes on the feed-in are irrelevant now or what do you mean?

For me, paying taxes means that I have to pay money on the generated electricity, even though I could use it "free of charge" for my own consumption without having to buy any from the supplier. Then I would be taxing the self-generated electricity, meaning paying money on top and then paying twice because I still have to buy some. I probably don't know enough about it. Maybe it makes sense to have another conversation with the architect and energy consultant here.

Well, they usually have little knowledge about that. With regular taxation, that's correct, you have to pay 19% on your self-used electricity. But there is also the small business regulation, where you don't have to do that.

Photovoltaics in EL are obviously cool since the material basically doesn't cost anything. Climbing around on the roof was a bit too risky for me... If you're already doing it in EL, why did you build it so "small"? What is that? 7 kWp? You don't have to feed in, but then it becomes a very expensive hobby. Taxes on feed-in are not relevant now, or what do you mean by that?

6.24 kWp My former schoolmate has a company that designed the system for me. I bought the material there. He said you don't necessarily need more; price/performance-wise this size is absolutely sufficient... you can always do more, but the wallet has to cooperate too.