[thecal]

I've used these for over a decade with limited success. Their performance is very specific to your wiring and can be fouled up with lots of things. Mine was sometimes no faster than WiFi. MoCA (Ethernet over coax wiring like for cable/satellite TV) seems to work better.

[Lammy]

I had a lot more success with them after popping my electrical panel open and rearranging the relevant outlet circuits to all be on the same AC phase (making sure not to unbalance the amperage load since some were 15As and some were 20)

[function_seven]

I can't believe I haven't thought of that!

I'm using a pair of TPLinks to feed a wifi router on the opposite side of my house. The outlets are definitely on opposite phases, but the powerline adapters still work reasonably well. (~80Mbps). Now I'm realizing I should probably swap a couple of circuits and improve that connection.

[EricE]

It would be far easier to just get a phase coupler http://cache-m2.smarthome.com/manuals/4826a.pdf

But brute force works too :)