Power Nap

Power Nap, available on Mac computers with flash memory (not for Mac computers with a hard disk or solid-state drive), lets some Mac computers stay up to date even while they’re in sleep. When the Mac goes to sleep, Power Nap activates periodically to update information. The information that’s updated depends on whether your Mac is running on battery power or plugged into a power adapter.

When your Mac is in sleep and using battery power, Power Nap:

• Checks for new messages in Mail

• Updates events in Calendar

• Updates other iCloud events

When your Mac is plugged into a power adapter, Power Nap can also do Time Machine backups.