Well my upstairs and downstairs are on different breakers but I am in UK.

From what I read at the time was that as long as the whole system is part of the same consumer unit then everything would be ok.

I have a pair to get from one side of the room to another then one in each of the bedrooms for my wife and myself with no detriment.

I suppose the sensible advice would be for everyone who is interested to give it a go. It has been running without issue for me for nearly two years now.

Power line adaptor. I have them in my house and zero loss in speed/latency/dither. Your house electrics have to be ok though.