Photovoltaic system offer for our single-family house

I wouldn’t fully agree with that… regarding the feed-in tariff

You don’t have to. But having 11 months more or less, so almost a whole year, does make a difference. But everyone can decide that for themselves. It was just a recommendation. ;)

fully north-facing, or at least a full string (usually around 20 modules). With the low roof pitch, it's worth it.

Up to what roof pitch is it worth it with the north-facing roof?

That depends, as so often, on many factors. The most important is the purchase price. Specifically, only the one that comes "only for additional north" on top. And that is often not even that high, since the inverter hardly gets any more expensive, the electrician not at all, the paperwork neither... You basically just have to coax it out of the solar installer, preferably by having them make a clearly itemized offer and then only add the roof mounting, modules, and substructure.

In short: Up to 25° I would install immediately. In the south up to 30°. If north is not exactly north but rotated 20° toward east or west, a few more degrees are also possible. And if you build yourself (for €700 per kWp) then practically every north roof.

If you want, you can also recalculate it on that one EU website, which must not be named: Everything from 700 kWh/year per installed kilowatt is worthwhile.

Heat pumps further increase the benefit of north as well, since winter foul weather delivers the same (low but helpful) yield regardless of orientation.

Another advantage: Those who really have a proper, shade-free south roof often run into the 70% curtailment. As soon as a north roof share is added, nothing is curtailed anymore.

much has already been said. Especially the utilization of the north side. At 25°, I wouldn’t hesitate for a second. SolarEdge always costs more. The wiring effort is higher, more electronics on the roof. The very long warranty with SE often does not justify the extra cost. And I also see no added value in the monitoring of individual modules that is possible with SE. The 5 lonely modules on the north side, of course, run with SE; with "normal" inverters such a short string usually doesn’t start, especially on the north side. But since I would "fully" utilize them anyway, that argument falls away. ;)

Hi guys, first of all I want to thank you all for the many helpful comments. As a layperson, you just hope that the solar installer / electrician knows their craft and offers / sizes everything correctly, but apparently that is not the case ;) I will read through everything again calmly over the weekend, but here is what I am already taking away: - rather leave out the storage - rather fill the roof completely - definitely cover the north side of the roof more than currently planned --> is that correct? PS: Our house roof is actually oriented almost exactly north/south... the deviation is about 7-8 degrees...

Oh, and one more thing I wanted to add: according to the development plan, photovoltaic / solar as an independent roof surface is even explicitly allowed... but somewhere I read that you should still use tiles and then install the system on top. Deliverer, however, wrote something about metal instead of tiles. That would practically be a photovoltaic roof surface, more or less?