A nap, a siesta, a power nap, the concept stays the same: dozing off briefly by day to carry on afterwards with more energy.
Siesta or power nap
A siesta and a power nap are not the same. A power nap is short and strong: an energy boost. A siesta lasts two to three hours. People confuse them regularly.
What a power nap yields
Dozing for 15 to 20 minutes benefits concentration, memory and the immune system. NASA research showed this. Pilots who took a short nap during long flights performed measurably better on attention and reaction speed.
The timing
The trick is in the timing. Waking in a light sleep phase gives the energy boost. Waking in the wrong phase gives grogginess. That is why a nap that is too long has the opposite effect.
No replacement
Three power naps are no replacement for one night's sleep. At night you sleep deeper and more efficiently. A nap is a temporary measure. Not a remedy for structural sleep deprivation.