If you're forced to run your notebook without AC (on an airplane, for example), maximizing battery life is crucial. Like most of its predecessors, Windows Vista supports various power schemesVista calls them power plansthat specify different time intervals for when the notebook is plugged in and when it's on batteries. However, it's equally important to monitor the current state of the battery to avoid a shutdown while you're working.

Monitoring Battery Life

To help you monitor battery life, Windows Vista displays the Power icon in the notification area. When you're running on AC power, the Power icon also includes a plug. When you're on batteries, the Power icon displays without the plug, and is completely green. As your notebook uses up battery power, the amount of green decreases accordingly.

To see the exact level of battery power remaining, you have three choices:

• Open the Mobility Center (as described in the previous section) and examine the Battery Status display.

• Hover the mouse pointer over the Power icon. After a second or two, Windows Vista displays a fly-out that tells you the approximate time left on battery power and percentage of battery life remaining.

• Click the Power icon. Windows Vista displays a larger fly-out that not only shows you the approximate time left on battery power and percentage of battery life remaining, but also enables you to change the current power plan (Balanced, Power Saver, or High Performance).

Specifying a Power Plan

Windows Vista shuts down some system components in an effort to keep your battery running longer. This is controlled by your current power plan, a power-management configuration that specifies which components get shut down and when Windows Vista shuts them down. Windows Vista has three power plans:

• Power Saver Devices such as the screen and hard disk are powered down after a short idle interval. For example, on battery power, Windows Vista turns off the notebook screen after 3 minutes and the hard disk after 5 minutes.

• High Performance Devices are powered down only after a longer idle interval, which improves performance because you're less likely to have to wait for them to start up again. For example, on battery power, Windows Vista turns off the notebook screen and hard disk after 20 minutes.

• Balanced This is the middle road (more or less) between the Power Saver and High Performance plans. For example, on battery power, Windows Vista turns off the notebook screen after 5 minutes and the hard disk after 10 minutes.

The default power plan is Balanced, but Windows Vista gives you three methods to change it:

• Using the Mobility Center In the Battery Status section, use the drop-down list to select a power plan.

• Using the Power icon Click the Power icon, and then click the power plan you prefer.

• Using the Power Options window Double-click the Power icon to display the Power Options window, then click a power plan option.

Creating a Custom Power Plan

Vista's preset power plans are probably fine for most uses, but you might want to tweak some plan characteristics. For example, you might want a plan that never turns off the hard disk or that waits longer before turning off the display when the notebook is on AC power. For these and other custom plan settings, Vista gives you two choices:

• Create your own plan You can set up a new plan that specifies the intervals when Vista turns off the display and puts the computer to sleep both on battery and while plugged in. In the Power Options window, click Create a Plan to get started.

• Customize an existing plan This method gives you much more choice for your custom power plan configuration. In the Power Options window, click the Change Plan Settings link under the plan you want to customize. The Edit Plan Settings window enables you to change the intervals when the display is turned off and when the notebook goes into sleep mode. For more options, click the Change Advanced Power Settings link. This displays the Advanced Settings tab, which offers a wide range of power-management settings.

Configuring Your Notebook's Power Buttons

Most newer notebooks enable you to configure three "power buttons": closing the lid, using the on/off button, and using the sleep button. When you activate these buttons, they put your system into sleep or hibernate mode, or turn it off altogether. On some notebooks, there isn't a separate sleep button; you simply tap the on/off button quickly.

To configure these buttons for power management in Vista, open the Power Options window and click the Choose What Power Buttons Do link to see the System Settings window. Use the lists to configure the power button, sleep button, and lid switch for battery power and AC power.