Just like it did earlier this week for the 2011 and 2012 MacBook Airs, Apple, today, has released a new firmware update for the 15-inch MacBook Pro with Retina display to enable the PowerNap feature. PowerNap allows your Mac to update iCloud files, emails, software updates and more while in sleep mode. Users can get the update via the Mac App Store software update section.
After updating users will see the following option in System Preferences:
Full PowerNap info below: