JFYI, for measuring power draw, you might be able to use `macmon`[0] to see the total system power consumption. The values reported by the internal current sensor seem to be quite accurate.
Very nice tip, thank you!
I measure around +11W idle. While running a speed test, I read ca. +15W.
Speaking of hardware, the RTL8159 (10Gbps) hit the market late last year and is said to consume only about 2–3W. It apparently runs very cool compared to older chips. (Though it would need to be bonded to reach 25Gbps ;-)