OS X Mountain Lion 101: Power Nap

Many people have been asking about the PowerNap feature on OS X Mountain Lion. Basically this feature enables the Mac to be in sleep mode and still do a lot of stuff, like:

• Mail - receive new messages.
• Contacts - your Contacts update with any changes you may have made on another device.
• Calendar - receive new invitations and calendar updates.
• Reminders - reminders updates with any changes you may have made on another device.
• Notes - notes updates with any changes you may have made on another device.
• Documents in your iCloud account - iCloud pushes any edits you made to a document to your Mac notebook.
• Photo Stream - your Photo Stream updates with new photos from your iPhone, iPad, or iPod touch.
• Mac App Store updates - your Mac notebook can download updates from the Mac App Store.
• Time Machine backup - your Mac notebook can back up while it sleeps.
• Find My Mac - locate a lost Mac notebook even when it’s sleeping.
• VPN on demand - corporate email updates securely.
• Configuration profile - Macs in managed environments can receive configuration profile updates.

When plugged in to a power source:

• It can download software updates
• Make backups with Time Machine
• Perform Spotlight indexing
• Continue Mac App Store downloads 
• Updates Help Center

All this is done without having a single light or fan on.

But his feature isn't available for all Macs running OS X Mountain Lion. Models supported are:

• MacBook Air (Mid 2011 and 2012)
• MacBook Pro (Retina, Mid 2012) 

These Macs need to have OS X Mountain Lion and a separate firmware download installed in order to work. For the MacBook Air Mid 2011 you can download the firmware here, the Mid 2012 MacBook Air firmware can be downloaded here. The firmware for the MacBook Pro Retina is coming soon.