There were Government Programs like 20 years ago calles something like 10.000 roof program, after that came 100.000 roof program

and so on
For green enthusiasts and finance guys I think it wasalways a financial benefit to install a rooftop solar sytem for like at least 10m² ( just guessed that)
Also liek 10 years ago the government and the KfW did renew a deal for which you got a credit to be able to pay for a whole system on your roof ( like 20k€) and with the back then guranteed payment for each kWh you deliver into the power grid you got paid money, that was guranteed by government at the beginning ( guessed 0.30€/kWh ) So after say 15 years you will make plus overall and that was guranteed as well, you only had to do the math.
That is why a lot of people did actually get a solar system on their roof, just like my parents did. Then what happened now is, there are too many of those system, so govermnet has to pay too much money for the injected power, so they cut down on the guranteed

money you get.
Solar power is not paying for itself either, big companies going bankrupt, since china is manufacturing way cheaper, and so on simple capitalism

but what stays are the solar systems on the roofs, which actually work pretty fine, no doubt about that, and gladly we still got some big solarinverter companies producing in germany as well like sma.
Thats the story behind it, from my memory, I am sure a lot of people have deeper inside and some of my figures are not right, but overall thats the impression
