How that? If the energy demands of the base functionality already differs between a consolidated all in one and a decentralized BYOD solution, how is adding essentially the same number(s) to both sides of the inequality change that absolute difference?
I grant you that the relative difference between the solutions will get smaller, but I for one have to pay my absolute energy consumption, so X awatts more or less makes a noticeable difference to me.
Full disclosure, I am running a mixture of consolidated and decentralized:
bt homehub5a as bridged modem ~7W
turris omnia as dualband WiFi router ~8 W (running SQM/pakon IDS)
gigaset c610ipa, VoIP basestation ~1.4W
total: ~16-17 W
This already consumes more than a modern top of the line all-in-one modem-WiFi-router like a Fritzbox 7590 (estimated ~11-15W depending on usage patterns). I doubt that exchanging the omnia with a wired only router an a dual band AP would not add noticeably more to this difference...
(These are averaged numbers over multiple hours to days, so reflect the average consumption well. I prefer longer term averages over simply trusting idle power values taken from datasheets, but then I can measure longer term energy consumption reasonably well, instantaneous power less so).
Sidenote: Over here is an attempt to collect typical energy consumption numbers for devices in a home network, to allow better informed decisions when taking expected energy consumption into accpunt when designing/extending a home network.