The perfect nap length is considered to be at least 90 minutes.
A nap of between 14 to 20 minutes is called a power nap which helps refresh you when you need a quick nap.
However if you need a longer nap to give you more energy then taking a nap of at least 60 to 90 minutes will help recharge you.
While the kids are at school I will try to take at least a 90 minute nap in the afternoon about a few hours before the kids get back from school.
Without the nap I would be too exhausted once my kids get home.
I also have a 2 year old boy who takes a nap for 90 minutes as well and I try to get a nap during that time too when he's asleep.
Once he wakes up I cannot get any rest.
I love my kids but they are exhausting.