Although we are drifting far from the topic of storage, most of that has already been said. Economically and especially environmentally, it’s not really a good idea.
Regarding the north side: As mentioned, you have to calculate it concretely. My numbers were just an example. When you look around on the internet and some other forums, I also don’t think they are bad/wrong. Maybe your figures are net?
However, I never said that the north is cheaper because it is in the north, but simply as a "volume discount through synergy effects." I don’t find a 30% discount unreasonable when you look at how cheap photovoltaic modules are in purchase. Additionally, you could also factor in the effect that the 60/70% capping limit with north installation brings advantages for the south side.
For the environment, it applies that photovoltaics pay off environmentally after 5 years. On the north side, that’s about 7 years. I still find that pretty good!
We are probably getting a 45-degree roof, which corresponds to a disadvantage of over 50% on the north side; for that, you can really only do self-installation.
1. Difference between a pure "south system" and a combined north/south system results in a surcharge for the north expansion and therefore a separate kWp price for the north. The inverter may only need to be sized larger, grounding only one cable, additional cabling effort lower, volume discount on modules etc.
2. Capping limit is avoided
3. Yield in the north (or east/west), albeit low, is generated when almost nothing comes from the south, so it is mostly used by oneself (base load)! Especially in the morning and evening. This brings the actual return from not purchased kWh (I am not talking about 7-8 cent feed-in tariffs, those are also okay).
4. The system does not vanish into thin air after 20 years!
Notes: The autonomy rate shown on offers is usually nonsense (only considered economically), every!! profitability calculation from a solar installer was dismantled within minutes and clearly proven to be calculated incorrectly.
Nevertheless, almost every photovoltaic system (without storage) pays for itself; forget the 20-year "lifetime" (see above) .... It would have to be ridiculously expensive otherwise.
Outside of these purely economic considerations, of course there are also people who install photovoltaics on the roof for entirely different reasons ... :p
And people, please don’t constantly confuse kWp, kWh, kW ... ;)