This depends entirely on the size of your house. We're easily covered by a single wifi router. We also don't have easy to rewire walls... (Yay 1910 era construction. :) )
If your 110V wiring is vintage 1910, you should consider rewiring anyway. I was involved in renovating a 1923 building, and the old wiring was neat, but terrifying. Pulled it all out, didn't even want to think about anyone trying to run power through it.
Yeah, we've already upgraded the electric. Definitely could have rerun ethernet then, but did not want to deal with moving any outlets. (Or, really, thinking about the problem hard. We have barely 1000 sq ft, so not hard to cover with wifi.)
Fair. My point is a lot more valid if you are tying to put something that needs a lot of space, like hvac. Wires are probably not that difficult to get in.
