Naps are a great source of comfort for some.  The biggest question being how long should I nap and what benefits are derived from these naps.  Here are some guidelines:

10 to 20 minutes
This power nap is ideal for a boost in alertness and energy, experts say. This length usually limits you to the lighter stages of non- rapid eye movement (NREM) sleep, making it easier to hit the ground running after waking up.

30 minutes
Some studies show sleeping this long may cause sleep inertia, a hangover-like groggy feeling that lasts up to 30 minutes after waking up, before the nap’s restorative benefits become apparent.

60 minutes
This nap is best for improvement in remembering facts, faces, and names. It includes slow-wave sleep, the deepest type. The downside: some grogginess upon waking up.

90 minutes
This is a full cycle of sleep, meaning the lighter and deeper stages, including REM (rapid eye movement) sleep leads to improved emotional and procedural memory (i.e. riding a bike, plating a piano) and creativity. A nap of this length typically avoids sleep inertia, making it easier to wake up.