Which empty conduit is suitable for photovoltaics

It's a question of the system and the arrangement. Wiring requirements can certainly vary. As a rule, the proposed thin tubes are sufficient. If not, it was foolish not to have specifically informed yourself.

Yes, I wonder how one can recommend only one conduit for a carport with a gable roof.
There is a possibility that two strings are used due to east/west orientation.
Therefore, I said 2x M25.
In addition, there are electricians who prefer to run the grounding separately.

Better one conduit more, better a size bigger, than to regret it later.

Apart from that, there is also option B, to install the inverters on the carport and to supply the carport overall with only one "thick" underground cable from the house, to take e-mobility into account. This results in additional costs for a small sub-distribution at the carport, but only requires one line from the house to the carport.

It's a question of the system and the arrangement. Wiring requirements can certainly vary. As a rule, the proposed thin conduits are sufficient. If not, it was silly not to have looked into it specifically.

Very good point. I hadn't looked into it beforehand and just let the electrician do it. Result: a relatively thin empty conduit.

Since I later independently decided on a solution with only one string, it worked out. For a typical system, however, the empty conduit probably wouldn't have been sufficient despite "photovoltaic preparation."

Aside from that, there is also option B, which involves installing the inverters on the carport and connecting the carport overall to the house only with a "thick" underground cable to accommodate e-mobility. Additional costs arise for a small sub-distribution at the carport, but only one line is needed from the house to the carport.

An inverter or a wallbox requires a network connection. If you don’t have good Wi-Fi coverage there, install a separate thin conduit for network cables into the house.

Direct hit at East/West
So, 2 empty conduits. I only make the empty conduits for contingencies. I could imagine that at some point in the distant future there will be a requirement for photovoltaics, and then I wouldn’t have to tear everything up extensively. Currently, I will not implement a system, I would have to finance everything externally and then there is hardly any profit left. I have too many other projects to take on photovoltaics just for environmental reasons.

Argh, network cable needed? Then I would have to thread another cable through the multi-duct. The power cable for the shed is already in the same entry as the Telekom fiber optic cable. Hopefully that will still work additionally with the network cable without loosening the Telekom cable. At least the civil engineers warned against doing that afterward.

In case of uncertainty, I would simply overdimension, e.g. lay 2x HT10, you can always make use of that and it doesn't cost much more.

Is 5 x 10 mm NYM sufficient or should it rather be 5 x 16 NYM?