A little while ago, I was wondering to myself how much power the brain uses. Today, BoingBoing helped me answer that question:
The brain consumes 20 percent of your body’s energy, but what for? Turns out a third of the energy is spent on “housekeeping.”
I crossed check this and 20% appears to be dead on (see http://hypertextbook.com/facts/2001/JacquelineLing.shtml). As it turns out, it’s also about 20 Watts of power to run the brain (on a roughly 2000 food calorie diet).