> Lack of distribution costs
What are the "distribution costs"? Presumably any cost besides the cost of infrastructure to connect to the grid are negligible, and you have to pay the infrastructure cost anyway (or rather, if you pay to over provision on production and storage such that you can be truly off-grid, then you're going to be paying far more than the infrastructure costs).
> Distribution of maintenance costs. Right now the biggest cost is installation. But it doesn't seem at all infeasible that this could be simplified to the point that it is something that people could easily install themselves.
I doubt it. First of all, making plans based on some unknown innovation seems, uh, unwise to put it nicely. Secondly, it's very unlikely that such an innovation would reduce the cost of rooftop solar but not farmed solar. Thirdly, such an innovation seems very unlikely since we already have ubiquitous tasks that every home needs (electrical, plumbing, roofing, dry-wall) for which we still hire professionals--the ubiquity hasn't manifested an innovation that lowers the technical barrier enough that we all do these things ourselves.
Moreover, economies of scale work in the other direction. It's much cheaper to maintain a single 1MW solar farm than it is to maintain 50 20KW rooftop installations.
However, we don't need to speculate about tradeoffs. According to https://www.solarreviews.com/blog/what-is-a-solar-farm-do-i-..., rooftop solar costs 2-3 times as much as farmed solar, so it seems the economies of scale dwarf any advantages rooftop solar might convey.
> Places like Germany already have somewhat significant contributions from rooftop solar.
If I'm understanding https://en.wikipedia.org/wiki/Solar_power_in_Germany correctly, solar only accounts for 8.2% of German electrical capacity and of that 14% comes from rooftop solar. So something like 1% of Germany's capacity comes from rooftop solar?