Transmission infrastructure takes a lot of maintenance. Somebody's going to be paying for that, and nobody wants to lose money doing it. I don't know enough about the exact cash flows of the industry (and it probably is different for different utility companies), but there should be some reasonable way that individual solar (or wind, or whatever) power suppliers can pay their fair share of that.

As I said, I doubt that would be a very large number right now, but if it's true that huge numbers of such installations will someday come on line, they may one day be carrying most of that infrastructure burden.

The good news is that if millions of people are supplying power, even then the individual "cut" of the infrastructure costs still won't be all that large.

The only power company I have looked up information on is my own, Pacific Gas and Electric. It deals with a mixture of purchased power, and power generated by its own plants. As you say, the mixture probably varies quite a bit between companies, and it would be possible for a utility to deal mostly in distributing and maintaining power connections from other people's generators.

Such a company, ironically, might adapt most easily to distributing solar power from individual sources.