Photovoltaic system 120 sqm living area - cover the entire roof?

I tried it but found that the tilt of the north side (rel to the irradiation direction!!!) would have to be entered as negative.

Are you sure? That would be unfortunate, then nothing would be right. But PVSOL comes to almost the same result, as do the solar installers who work with it.

That is so unusual that I am interested in your calculation method. How do you calculate? What assumptions do you make?

Variant: Everything that goes on the roof: south side, 30 degrees, 36 sqm
2400 annual self-consumption, mostly in the mornings and evenings, no consumption during the day
The photovoltaic system with battery costs all in 25K, according to the calculator produces 8000, calculated as 6/7 of that, making a theoretical output of 6800.
I can theoretically feed in 4400
I calculate operating costs as 2% of the investment per year
Feed-in can cover the operating costs
I would have canceled the self-consumption after 20 years
If the system lasts until then or nothing else happens

Doesn't pay off for me. Or am I making a thinking error?

The advisor immediately dismissed a smaller system just for self-consumption.
The most expensive thing is the person. And whether he screws on 1 or 8 modules doesn’t make much difference... but it would have cost around 15.

Thank you for the overview. I did not quite understand the parameters.

2400 Eigenverbrauch Jährlich, meistens morgens und Abends, kein Verbrauch Tagsüber

2400 kWh is a low annual consumption. Congratulations. Your house has a base load that runs continuously, but it should be quite low given the annual consumption.

Die Photovoltaik Anlage mit Batterie kostet all in 25K, schafft laut Rechner 8000

Does that mean 8 kWp? What capacity does the battery have? The battery could quickly be oversized with such low consumption. 25k seems quite high to me, even if the parameters are not entirely clear. That seems to be the first sticking point.

6/7 davon gerechnet, macht eine theoretische Leistung von 6800.

Is that your conversion from kWp to annual yield? I don’t understand the 6/7.

4400 kann ich theoretisch einspeisen

Are you calculating the 6800 minus the 2200 here? You won’t cover 100% of your own consumption. Better calculate with 75%. What feed-in tariff are you expecting? What purchase price are you calculating with?

Betriebskosten rechne ich mit 2 % des Invests pro Jahr

You can do that. For the modules, 20 years are usually no problem; for inverters and batteries, that is not a given.

Is that your conversion from kWp to annual yield? I don't understand the 6/7.

85% is the usual value for conversion in Germany from kWp to kWh.

The photovoltaic system with battery costs all in 25K

That is definitely way too much for 8 kWp + a sensible battery.
A sensible battery for the system would be max 5 kWh.
Realistic price (net)
8 kWp system 10k
5 kWh battery 6k

Calculate the profitability with these parameters!

85% is the usual value for conversion in Germany from kWp to kWh.

Recommend using the PVGIS data for the calculation.

These are values that the solar technician once told me. One big factor was the labor cost, handling fees. Yes, everything calculated on an annual basis. 6/7 are for me the actual watts that I would get. Car manufacturers also state 5 liters for city driving, but in reality, it's a bit more. I once heard 6/7 somewhere as well. Covering self-consumption was the basis for the solar technician and the calculation, hence the battery. Ok, assuming I invest 16K, then the system - based on the same expected performance - is paid off after 16 years.