The power nap is a short nap usually 20-30 minutes in a dark quiet environment designed to provide a brief rest without entering deep sleep. A long nap can cause the sensation of grogginess or disorientation upon awakening (called sleep inertia in medical lingo) that can actually interfere with mental and motor performance up to several hours after awakening. We usually don’t enter deep sleep within 20 minutes of napping unless we are extremely sleep deprived or have a sleep disorder such as narcolepsy.
Power naps have been shown not to interfere with the circadian rhythm as long as they are not too close to bed time. Also, they have been shown not to effect total sleep time during the night’s sleep.
Where and how to power nap? At your desk, in your parked car, on a sofa, in a comfortable armchair, or in an Energy Pod (made by Metronaps). This is an example of the perfect nap environment: very comfortable, dark, and quiet.