

@just_an_average_joe
You are right that this setup needs a DC-AC inverter often sold together with the PV panel and the inverter is designed for this purpose. It sort of rides on the sine wave from the outlet. Yes, this only works on one phase while the building gets 3 phases, but practically it does not matter since the meter sums all three phases.
There was some debate over the technical standard and meter type, German bureaucracy and lobbying!
@bstix

We fought to make it legal and solar from the balcony just works. You plug the device into your regular 220V AC outlet.
Wikpedia has pictures https://en.wikipedia.org/wiki/Balcony/_solar/_power
In Germany you can buy those in home-improvement stores or online. Your local lidl or aldi might have one occassionally.
@bstix @just_an_average_joe