We legalized these in Belgium last year.
I bought a 1600Wc + 1.9KWh kit (Ecoflow Stream) for +/- 1300€ last summer. It took us about 2h to install (we had to setup a new plug outside), and I already saved 200€+ since July. I am expecting to save about 350€ per year.
Also, as u/jstch said, it's extremely fun to setup and generate your own power!
A 3.7 year ROI would be incredible (and fairly uncommon AIUI)
South facing?
And how does it work there?
You have special electric meter and you are distributing solar power into the grid outside of your household?
Or you don't distribute electricity into the grid?
Did you need to get it certified? I think the limit for DIY balcony panels here in Belgium was about 800W.