Hello.
I have now also found something, at first there were lots of search results about what size makes sense etc.
As I see it, the southern roof surfaces (deviating by 60 degrees to the east or west) are suitable surfaces, these must be covered with 60% of the area.
Alternatively 0.06 kWp per m² of built-up land area
"The photovoltaic requirement is considered fulfilled if the photovoltaic system has an installed minimum capacity of 0.06 kilowatt peak per square meter of the built-up land area."
"The built-up land area includes the area where a building touches the ground with its exterior wall, as well as roof overhangs that protrude beyond it."
14x12.5m house, and 9.2x7m garage = 239.4m² x 0.06 = 14.4kWp
That already adds up to quite a bit, I would not have thought so