How to Put Your Mac in Sleep Mode Automatically

You can make your Mac put itself in Sleep mode automatically after a fixed period of time. If your Mac doesn’t detect any keyboard or mouse activity within the length of time you have designated, your computer will put itself into Sleep mode automatically.

To make your computer go to sleep automatically, you need to define the following:

The inactivity time: The inactivity time defines how long your computer waits before putting itself into Sleep mode. This time can be as short as one minute or as long as three hours.
The parts of your computer to put into Sleep mode: The two main parts of your computer that you can put into Sleep mode are the hard drive and the display (your computer screen). Because the hard drive and the display consume the most power, putting at least one or both of these parts into Sleep mode can dramatically reduce the amount of power your Mac consumes while it’s asleep.

To define how your Mac should put itself into Sleep mode automatically, follow these steps:

Choose the Apple key→System Preferences. In the System Preferences window, click the Energy Saver icon (the light bulb) under the Hardware category.

(If you’re using a desktop Mac, skip the next step.)
In the Energy Saver dialog box, click the Show Details button.

The Energy Saver dialog box expands to show you the computer and display sliders.
Drag the Put the Computer to Sleep When It Is Inactive For slider and the Put the Display to Sleep When the Computer Is Inactive For slider to any value between one minute and three hours.

When the computer sleeps, the microprocessor in your Mac goes into a special low-voltage mode. (If you never want your Mac to go to sleep, drag the slider all the way to the right over the Never option.) When the display sleeps, the video signal to the monitor is shut off. (If you never want your display to go to sleep, drag the slider all the way to the right over the Never option.)
Select (or deselect) the Put the Hard Disk(s) to Sleep When Possible check box and then click the Options tab to define additional options.

If you don’t want to define additional options, click the Close button, and you’re done! When you click the Options tab, the Options pane appears. When you put the hard drive to sleep, the hard drive stops spinning. Because spinning a hard drive burns up energy and wears out your hard drive, putting a hard drive to sleep can help the hard drive last longer.
Select (or deselect) one or more of the following check boxes.

(Some check boxes won’t appear, depending on the type of Mac you have.)
- Wake When the Modem Detects a Ring: Useful for remotely accessing a Mac over the telephone line. (This option appears only if you have a modem connected to your Mac.)
- Wake for Ethernet Network Administrator Access: Useful for letting a network administrator access and configure a Mac over a network. (Selected by default.)
- Allow Power Button to Sleep the Computer: Lets you put your Mac to sleep by pressing the power button. (Selected by default. This option appears only on desktop Mac computers.)
- Restart Automatically after a Power Failure: Makes your Mac restart if its power gets abruptly cut off. (Deselected by default.)
- Show Battery Status in the Menu Bar: Displays an icon (called a menulet) to show how much charge is left in your laptop’s battery. (This option appears only on laptop Mac computers.)
Click the Close button of the System Preferences window or choose System Preferences→Quit System Preferences.

Clicking the Close button or quitting System Preferences saves your changes.