OK I measured power consumption with powerTOP.
This is quite tricky, but essentially the baseline power consumption on battery at idle with nothing but USB-C cards (or no cards) installed was:
3.59 W minimum
With the card installed at idle:
6.3 W minimum
So 2.71 W idle.
With the card installed doing heavy 2.5 GbE transfers:
12.4 W maximum
So 8.81 W when being pushed hard.
I also forgot to mention - there is very little heat output. After a series of 2.5 GbE tests my IR thermometer (aimed right at the controller IC) measured 33.3°C in a warm room of 25.3°C, that’s a delta of only 8°C over ambient. On the case itself the warmest component was the steel network port casing, it measured 29.6°C so it obviously provided some heatsinking but was barely warm to the touch.