@IrelandRocks Your proposed setup is fine. (I don't know what was going on with @ROBERTOJONES) One thing though - you'll be switching off your existing router's WiFi. You're replacing the WiFi...

@grizzo All Deco models are compatible with each other. https://www.tp-link.com/au/support/faq/2248/

@Cazmunich I also have brick/concrete, but 2 floors. I got some Ethernet cables run in the roof and down the outside for the ground floor and plugged the Deco's into those - works great. (Before that...

You are putting an ethernet cable through the wall between the old and new sections? Then yes. This has nothing to do with the power circuits....

There is one main SSID and another for guest. That's it.

@alawy103 Strange. Some kind of incompatibility with your router?