You could run cables down the roof and the outside outside of the wall which not particularly rare. Actually that's the case for one of the aerials on my roof. And piercing roofs isn't exactly uncommon. Aircon vents, chimneys, mountings for aerials etc. The thing with something like this is that it doesn't have to be an optimal solution which instantly solves all our problems, which is what a lot of people seem to demand when it comes to anything which is even vaguely green, it just needs to be cheap and easy and move us away from our reliance on fossil fuels. This, along with traditional solar, hydro, onshore and offshore wind, nuclear etc. all have their place.

ressources are not infinite and framing the problem as one of good being the enemy of perfect is disingenuous. Rooftop solar is a terrible idea when compared to the alternative - utility scale solar, installed at the right location, in the right way, with economies of scale; all while achieving everything you mentioned.

Rooftop solar has numerous problems, starting with structural considerations, scale, shading, imperfect angles, local grid congestion and so on. Why have everyone waste money on this when we could just install solar farms?

because even with the inefficiencies it more than pays for itself.

To bring it back: Governmental policy vs individual choice? If I, a consumer of electricity want to reduce my GHG impact, I can only lobby the source of my electricity so much. Rooftop solar might be less efficient than gridscale for the system, but it's something the individual can do.

Because we're not installing solar farms and are installing rooftop solar in many locations because land is limited and expensive and roofs aren't? Not everywhere has large amounts of empty land waiting to be built on

It’s not the holes for the cables that are the problem. It’s the anchor screws that mount the panels to the roof. If you’ve ever installed shingles on a roof you would know that you have to be careful to cover all of the nail heads with the next row of shingles and preferably use roofing tar as well to get a good seal. The anchor screws for solar are supposed to only go into the rafters below the roofing but anyone can tell you that is hard to do 100% of the time on an existing roof even if you are being meticulous and judging from the installs I’ve seen most solar installers aren’t.

> And are in the most difficult place for maintenance and cleaning, so those things will be neglected.

They don't need much service. And it's not like you need a helicopter to get there

> And you need to replace the roof? Now what?

That's one in 50 years event

Like yeah, if you have good amount of space that is otherwise unused go ahead, but realistically someone will want that space for a house or business, not a bunch of glassy squares, those can go on roof.

Or, in a utility solar farm, where they work well.

50 years? Where, Europe? With tile I’m guessing because in North America most people have asphalt roofs that need to be replaced every 15 to 20.

And get in the way of fire fighting[1].

[1]: https://brannredning.com/brann/brannen-asko-bygget/