Well, I just measured my 286. I give that it's not yours so the result won't be the same but it still says something. It idles at ~29W and consumes up to 37.5W while spinning up the hard drive. The config is as follows:
Octek Fox II 286 board (very small, heavily integrated Headland chipset) with a Harris 20MHz CPU
4MiB SIMM RAM
Cirrus Logic GD-5402 512kB VGA
Gravis Ultrasound Classic 3.74 (I know it's crazy but there are a few games and demos that can use it in a 286 😁)
ES688 for real OPL3 music and SB compatibility (yes, it has the Yamaha chip)
Standard ISA I/O card (probably Winbond based)
1.2M+1.44M FDD
840MB Quantum HDD
HP PS/2 keyboard
The power supply is a rather modern (for an AT PSU) 200-watt DTK piece. The other parts are relatively recent too and probably consume less power than old bulky hardware with a hundred logic chips on the mobo and the cards and an oldschool hot 286 (the 20MHz Harris CPU is definitely much cooler than, say, a 10MHz Intel one) yet I wouldn't think a more oldschool 286 could draw more than ~1.5x of this config. The only way to seriously outdo it would be a huge MFM hard drive. What does that sideboard do btw?
On a side note, the original IBM PC power supply was rated for 63 Watts and AFAIK it could cause problems with a combo of expansion boards and MFM drives.
Shame on us, doomed from the start
May God have mercy on our dirty little hearts