Is PoE more efficient than plugging in adapters for each network device?
And at what scale does it start to matter?
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From my perspective; I’m going for a 3 node mesh router, plus 2 switches, and was considering if in 5 years time the electricity difference would be less than the extra upfront cost. The absolute max length of cable would probably be around 30m
Considering the PoE switch is also powered by an adapter, I’d say no. Your have the same efficiency from the AC-DC conversion plus line losses.
Converting power once vs X times definitely has an efficiency factor.
Really depends. If you have 1 device that uses 10W with 90% efficiency, you lose 1 W. If you have 10, 1W devices with 90% efficiency, you lose 1 watt.
It is less efficient if X device has lower efficiency or if you have DC/DC converters in series (which is likely with PoE), but likely it is negligable difference.