Energy Saver Preferences on Your MacBook
The Energy Saver pane of the Hardware section of the System Preferences window is where you can help extend the life of your MacBook battery by getting familiar with Sleep mode.
Move the Computer Sleep slider to specify when Mac OS X should switch to sleep mode. The Never setting here disables sleep mode entirely. To choose a separate delay period for blanking your monitor, drag the Display Sleep delay slider to the desired period. You can also power down the hard drive to conserve energy and prevent wear and tear (an especially good feature for laptop owners).
If you want to start or shut down your laptop at a scheduled time, click the Schedule button. Mark the desired schedule (the Start Up or Wake check box and the Shut Down/Sleep check box) to enable them; then click the up and down arrows next to the time display to set the trigger time. Click OK to return to the Energy Saver pane.
Some of the settings can toggle events that control Lion’s sleep mode, including a network connection by the network administrator (Wake for Network Access). If you want the display to dim before your Mac goes to sleep, enable the Automatically Reduce Brightness before Display Goes to Sleep check box.
You can also set Mac OS X to restart automatically after a power failure, which is a good idea if you’re sharing music or files with others. By default, the Battery Status icon is shown in the Finder menu bar — however, you can click the Show Battery Status in the Menu Bar check box to deselect it and hide the Battery Status icon if desired.
Mac laptop owners can set two separate Energy Saver configurations by clicking one of the two tabs at the top of the pane:
Battery Power: Applies when their MacBook is running on battery power)
Power Adapter: Kicks in when the laptop is connected to an AC outlet
Your MacBook will automatically switch to the proper configuration when you plug or unplug your laptop.