The average human brain consumes energy at the rate of about 12.6 watts, which about 20% of the consumption rate for the whole body at rest, which is 63 watts.
The brain apparently has no switches and consumes energy at that approximate rate day or night, awake or asleep and possibly even during a coma.
I suspect some are "dim-wits," and as a result consume less than 12w of power....
—Resting metabolic rate: 1300 kilocalories, or kcal, the kind used in nutrition
—1,300 kcal over 24 hours = 54.16 kcal per hour = 15.04 gram calories per second
—15.04 gram calories/sec = 62.93 joules/sec = about 63 watts
—20 percent of 63 watts = 12.6 watts