After nearly four years in AA, I finally devised a concept of "higher power" that doesn't involve a deity, the group, the "fellowship", nature, the cosmos, the laws of physics, or any other person.
As a committed atheist since the age of 4, I have always known that things were "up to me", and that I could not/would not get help from some power that was "higher" or "greater" than myself.
So one day, in a meeting, while someone was discussing his higher power, I suddenly realized that when I am sober and sane, I am my own higher power; that when I am using (and by implication, not sane,) that I am my own "lower power".
This concept dovetails neatly into the idea that things were always up to me. I decided to have children; I decided to divorce; I decided to pick up a drink; I decided to drink while drunk; I decided that I was powerless over alcohol; and I decided to go to AA.
When I am sober and sane I am my own higher power.