I placed 4 PDL's and was wondering about a consumption of 20MW ongoing.
After waiting a while and looking at the detailed info I saw that the PDL's have max ammo but do not stop draw power. Just turn them off stops the power drain.

They don't have targets to shoot but drain constantly 5MW each.
I tested this with other waepons of the mod and had the same effect.
Somehow the power accumulation do not stop.