Turn Power Nap on or off on Mac
Power Nap lets Mac computers stay up to date even while they’re sleeping. When your 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 (a Mac laptop) or is plugged into a power adapter (a Mac laptop or desktop computer).
When your Mac is asleep and using battery power, Power Nap does the following:
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 activities such as downloading software updates and performing Time Machine backups.
If your Mac supports it, Power Nap is on by default when your Mac is plugged into a power adapter. You can easily change Power Nap settings.
Turn Power Nap on or off for a Mac laptop
On your Mac, choose Apple menu > System Settings, then click Battery in the sidebar. (You may need to scroll down.)
Click Options, click the pop-up menu next to Enable Power Nap, then choose an option.
Turn Power Nap on or off for a Mac desktop computer
On your Mac, choose Apple menu > System Settings, then click Energy in the sidebar. (You may need to scroll down.)
Turn on Enable Power Nap.
Note: This option is only available on Intel-based Mac computers.