With a bit of tweaking, I figured that enabling power management on
on "Audio codec":

	echo '1' > '/sys/module/snd_hda_intel/parameters/power_save';

helped a little bit.  But not that much.  Now on 4.14.33, I get 10h,
while on 4.16.1 I get 5h.

There is something else.

By the way, how do I make the above /sys/ tweak permanent on GuixSD?

-- 
Pierre Neidhardt