How much electrical power is required to operate the human brain?

The energy output of the resting adult human body is equal to the power of a 100 W electrical light bulb. Remarkably, the brain alone consumes 20% of the body's chemical energy, even though it accounts for only 2% of the body's mass. Metaphorically speaking, we all have a 20 W light bulb burning in our head, even when we lie still in complete darkness doing physically nothing.