@CaribConsult 

Form the information I got the powerline devices will need a SNR of about 50 to 60 dB. If the SNR ends up being lower then that will affect speed and can also prevent adapters from communicating.

If the noise is too great alternatives such as range extenders may be better or a Deco mesh network.

@Tony Thanks very much for replying to my post. Obviously noise is a factor and we have quite a bit of it from the various inverters, gateway, Tesla PW and Enphase Envoy (a PV monitor...works nicely) and a peek inside the Gateway reveals at least two sets of ferite cores at different locations, and I put a pair on the feed to the Envoy to improve its powerline communications with the 21 inverters on the roof. Lots of signaling going on. 

I have an EOP setup of 4 TP Link 500Mbps units, and they seem to stay connected, althought throughput speeds can be anywhere from ~50Mbps to ~200+Mbps. Not exactly fibre optic, but plenty fast enough to allow the Tesla and the Envoy to report to their respective companies so I can monitor behavior with a website or a phone app.  No video or gaming or any of that high volume stuff is going over the EOP net, only data, and staying connected is the main objective.  They seem to be doing that. Do you have any idea how to measure S/N ratio on a powerline? I have a pocket scope. Do you know how this is done?  Thanks for your input

@CaribConsult 

I checked with one of our testers and you can measure the noise with a Oscilloscope which is not cheap.

A alternative is to use the powerline utliity app, and monitor the link rates, if the rates are consistant then you are good. If the link rates change values dramatically then that line has too much noise.