My ESXi box draws 20 watts at idle with 3 Windows VMs and 3 Linux VMs.

Guess which of those VMs draws the most power (hint: it's not Windows).

Power draw depends on more than the base OS, what it does matters so much more. Which is why my one Linux VM draws the most power - it gets used for some intense tasks with ffmpeg.

Interestingly, I've found little power draw difference using ffmpeg on Windows or Linux. Both will max CPU while converting and take a similar amount of time.