Leon444 wrote: Yes, it is possible

another issue is the huge charges in C11 for the connected power

but this probably affects everyone and has nothing to do with PV.
This is what it is about changing the tariff to G11
before assembly of photovoltaics. Because mounting panels not on a building requires a permit. So since the building exists and the panels are mounted on the roof, then no energy supplier
has no right to deny the G11 tariff to a private recipient !!! This is why I referred to the topic about tariffs.
Added after 2 [minutes]: marcin55 wrote:
And how did you switch to G11 (or there G12W) what happened with the accumulated kWh?
Get it out of your head. Photovoltaics is for individuals, you must be
prosumer that all these regulations apply to you. Otherwise you have to apply for a license to trade in energy.