I’m actually using powerline adapters, what you are talking about right now, but it’s not amazing. It’s decent, and much cheaper than coax. It’s a decent solution, but it is very limited by range. The best usage of it would be to have a short powerline adapter bridge to a better area for a wireless access point / router. Which is what I’m using it for.
The problem with the powerline adapter is that it loses a serious amount of performance the further away you go from the source powerline adapter. If there is a high-bandwidth isp connection, it’s not a huge issue, but with a low bandwith connection, like I have, it just becomes not great. Better than just have wifi in a bad area, but not great. Also they really don’t take well to having multiple powerline adapters running on the same power network. That’s why I wanted to try cable, since it preserves much more of the connection, and doesn’t run on the power infrastructure in my house, which isn’t that great.