Power management settings control the behavior of a computer in different power use situations, such as when it is plugged in or running on a battery. Although all computers should be configured with power management settings to save energy, power management settings on laptops help to balance performance against energy usage. In some cases, you'll want to reduce laptop responsiveness and overall performance to increase the battery life, enabling the laptop user to run the laptop on battery for longer periods of time. In other cases, you might want to ensure moderate performance and a moderate battery life or you might want to ensure maximum performance regardless of how this impacts battery life.
In Windows Vista, the core aspects of power management are streamlined significantly and are managed using power plans. Like power schemes in earlier versions of Windows, power plans are collections of power management settings that control power usage and consumption. A laptop can have multiple power plans, but only one can be active at any given time. In addition to power plans, most laptops have preset behaviors for when the laptop is closed, for when the power button is pressed, and for when the sleep button is pressed. Typically, closing a laptop's lid puts it into sleep mode, pressing and holding the power button shuts down a laptop, and pressing the sleep button puts it into sleep mode. Through system-wide settings for power options, you can customize the power button and password protection on wake behavior to meet the needs of individual users or groups of users.
On laptops and Tablet PCs, the notification area of the taskbar includes a Power icon. Moving the mouse pointer over this icon shows the battery state and the power plan you are using. You can right-click the Power icon to display a shortcut menu with options for quickly accessing the Power Options utility and Windows Mobility Center. Windows Vista has three default preferred power plans:
Balanced A power usage plan that balances energy consumption and system performance. The processor speeds up when more resources are used and slows down when less are needed. This is the default power plan. Use this plan for users who work with a wide variety of applications, including those that are moderately graphics intensive, such as Microsoft PowerPoint, and those that are not graphics intensive, such as Microsoft Word and Microsoft Outlook.
High Performance A high-power usage plan that optimizes the computer for performance at a direct cost to battery life. This plan ensures that you always have enough power for using graphics-intensive programs or playing multimedia games. Use this plan when performance is essential and users work primarily with graphics-intensive applications or applications that perform complex arithmetic calculations.
Power Saver A low-power usage plan designed to reduce power consumption. This plan slows down the processor to maximize the battery life. Use this plan for users who work primarily with non–graphics intensive applications, such as Microsoft Word and Microsoft Outlook.
Power plan settings are divided into two general categories: basic and advanced.
Basic power settings control when a computer turns off its display and when it turns off. By default, with the Balanced plan and the Power Saver plan, Windows Vista turns off the display after 20 minutes of inactivity and puts the computer in sleep mode after an hour of inactivity. With the High Performance plan, Windows Vista turns off the display after 20 minutes of inactivity but never automatically puts the computer in sleep mode.
Advanced power settings determine precisely whether and when power manageable components on a computer are shut down and how those components are configured for performance. Following are the advanced power settings you can configure:
Additional Settings\Require A Password On Wakeup Determines whether a password is required when a computer wakes from sleep. You can set this option to Do Not Lock Console When System Wakes or Require A Password On Wakeup.
Hard Disk\Turn Off Hard Disk After Determines whether and when a computer's hard disk is turned off to conserve power. Use a setting of Never to disable turning off the hard disk. Use a specific value in minutes to determine how long the computer must be inactive before the hard disk is turned off. Windows Vista provides a combo box for setting numeric values. Clicking and holding the up or down arrow enables you to rapidly scroll through values. If you scroll down from 1, the next value is Never. You can also type values directly. If you enter a value of 0, this is interpreted as Never.
Wireless Adapter Settings\Power Saving Mode Specifies the power saving mode to use with any wireless adapters connected to the computer. You can set this option to Maximum Performance, Low Power Saving, Medium Power Saving, or Maximum Power Saving.
Sleep\Sleep After Determines whether and when a computer enters a sleep state to conserve power. Use a setting of Never to disable this feature. Use a specific value in minutes to determine how long the computer must be inactive before the computer enters a sleep state.
Sleep\Allow Hybrid Sleep Specifies whether the computer uses Windows Vista's sleep mode rather than the sleep mode used in earlier versions of Windows. You can set this value to On or Off. Windows Vista's hybrid sleep mode puts the computer in a low power consumption state until the user resumes using the computer. When running on battery, laptops and Tablet PCs continue to use battery power in the sleep state, but at a very low rate. If the battery runs low on power while the computer is in the sleep state, the current working environment is saved to the hard disk and then the computer is shut down completely. This final state is similar to the hibernate state used with Windows XP.
Sleep\Hibernate After Determines whether and when a computer hibernates to conserve power. When a computer goes into hibernation, a snapshot of the user workspace and the current operating environment is taken by writing the current memory to disk. When a user turns the computer back on, reading the memory from disk restores the user workspace and operating environment. In Windows Vista, this setting isn't normally used because the standard configuration is to sleep after a period of inactivity. Use a setting of Never to disable this feature. Use a specific value in minutes to determine how long the computer must be inactive before the computer hibernates.
Sleep\Allow Programs To Prevent Sleep Determines whether programs can prevent a computer from entering sleep mode. If you set this option to Do Not Query Applications And Services, applications and services with active processes do not prevent the computer from entering sleep mode. If you set this option to Query Applications And Services, applications and services with active processes can prevent the computer from entering sleep mode.
Power Buttons And Lid\Power Button Action Specifies the action to take when someone pushes and holds the computer's power button. You can set this option to Sleep, Hibernate, or Shutdown.
Power Buttons And Lid\Start Menu Power Button Sets the default action for the Start menu's power button. Use this setting to override the computer's default action. You can set this option to Sleep, Hibernate, or Shutdown. You cannot, however, use an option that is not supported by the computer.
PCI Express\Link State Power Management Determines the power saving mode to use with Peripheral Component Interconnect (PCI) Express devices connected to the computer. You can set this option to Off, Moderate Power Savings, or Maximum Power Savings.
Processor Power Management\Minimum Processor State Sets a minimum performance state for the computer's processor. To save power and reduce energy consumption, lower the permitted minimum performance state. But you lower the performance state at a direct cost to responsiveness and computational speed. For example, a value of 5% would lengthen the time required to respond to requests and process data while offering substantial power savings. A value of 50% helps to balance responsiveness and processing performance while offering a moderate power savings. A value of 100% would maximize responsiveness and processing performance while offering no power savings.
Processor Power Management\Maximum Processor State Sets a maximum or peak performance state for the computer's processor. To save power and reduce energy consumption, lower the permitted maximum performance state. But you lower the performance state at a direct cost to responsiveness and computational speed. Although reducing the maximum processing power to 50 percent or below can cause a significant reduction in performance and responsiveness, it can also provide a significant power savings.
Display\Turn Off Display After Determines whether and when a computer's display is turned off to conserve power. Use a setting of Never to disable this feature. Use a specific value in minutes to determine how long the computer must be inactive before the display is turned off.
Display\Adaptive Display Specifies whether Windows Vista automatically adjusts when the display is turned off based on mouse and keyboard usage. You can set this option to On or Off.
Multimedia Settings\Media Sharing Action Determines whether media sharing can prevent a computer from entering sleep mode. If you set this option to Prevent My Computer From Sleeping After A Period Of Inactivity, the computer will not enter sleep mode when sharing media with other computers or devices. If you set this option to Take No Action, the computer can enter sleep mode after an appropriate period of inactivity regardless of whether media is being shared with other computers or devices.
As you can see, the advanced power settings control every facet of power management. The differences in the advanced settings are what really set the power plans apart from each other. For example, while the High Performance plan ensures performance by allowing the computer's processor to always run at 100 percent power consumption, the Power Saver plan reduces energy consumption by configuring the processor to use a minimum power consumption rate of 5 percent and a maximum rate of 50 percent. The Balanced plan, on the other hand, configures the processor to use a minimum power consumption rate of 0 percent and a maximum rate of 100 percent.
When configuring power plans, it is important to allow components to turn off after periods of inactivity. Turning off components separately enables a computer to progressively go into sleep mode. When a computer is fully in sleep mode, all power-manageable computers are switched off so that the laptop uses less power. When the computer is brought out of sleep mode, the components, such as the monitor and hard disks, are turned back on, restoring the user workspace. You should configure sleep mode so that when a laptop is running on batteries, it goes into power conservation mode when the user is away from the laptop for a relatively short period of time, such as 20 or 30 minutes.
Because a computer can have multiple power plans, each plan can be optimized for the way a laptop is used at a particular time. You can configure multiple power plans for different situations. At home or in the office, laptops might need different power management configurations than they do when users are giving presentations. In one case, you might want to configure the laptop to quickly conserve energy when running on batteries. In another case, you might want to ensure that the laptop never turns off its hard disk or wireless adapters.
Although computers can have multiple power plans, only one can be active at any given time. To select or optimize a power plan, follow these steps:
Click Start and then click Control Panel.
In Control Panel, click System And Maintenance and then click Power Options.
As shown in Figure 1, you can specify the power plan to use by selecting it in the Preferred Plans list.
Figure 1: Choose a power plan.
Click Change Plan Settings for the plan you want to work with. This displays the Edit Plan Settings page, shown in Figure 2.
Figure 2: Configure power plan settings.
Use the Turn Off Display list to specify whether or when the computer's display automatically turns off. Choose Never to disable this feature.
Use the Put Computer To Sleep list to specify whether or when the computer automatically enters sleep mode. Choose Never to disable this feature.
If you want to configure advanced options, click Change Advanced Power Settings. Use the settings in the Power Options dialog box, shown in Figure 3, to configure the advanced settings. Click OK.
Figure 3: Use the Power Options dialog box to configure advanced power options.
Click Save Changes to save any changes you've made.
In addition to the preferred power plans included with Windows Vista, you can create power plans as needed. To create a power plan, follow these steps:
In the left pane, click Create A Plan. This displays the Create A Power Plan page, shown in Figure 4.
Figure 4: Create a power plan.
To prepopulate the power plan settings, select the preferred power plan that is closest to the type of plan you want to create.
In the Plan Name field, type a descriptive name for the plan and then click Next. This displays the Edit Plan Settings page.
Click Create to create the plan. The Power Options page is displayed with updates to include the plan you created as a new preferred plan that replaces the plan you selected while creating the plan. You'll find the original preferred plan under Additional Plans. Click the Expand button on the right to display the plan.
The plan you created is selected by default. Click Change Plan Settings for this plan to display the Edit Plan Settings page and then click Change Advanced Power Settings to display the Power Options dialog box.
After you configure the advanced power options as appropriate, click OK and then click Save Changes to save any changes you've made.
System-wide settings for power options enable you to customize the way the power button and password protection on wake works. You can configure the power button so that when it is pressed, the system shuts down, hibernates, or enters sleep mode. You can configure the computer so that when it wakes from sleep, a password is either required or not required to unlock the screen.
To set system-wide power settings, follow these steps:
In the left pane, click Choose What The Power Button Does.
Use the When I Press The Power Button list to specify whether the computer should shut down, sleep, or hibernate when the power button is pressed. (See Figure 5.) You cannot, however, use an option that is not supported by the computer.
Figure 5: Set the power button and password protection on wake behavior.
Use the Password Protection On Wakeup options to specify whether the computer requires a password on wakeup. It is a good idea to prompt for a password to help ensure the security of the system.
Click Save Changes when you are finished making changes.
Windows Vista includes the Power Configuration (Powercfg.exe) utility for managing power plans from the command line. You can view a list of options for this utility by typing powercfg /? at a command prompt. The parameters you'll work with most often include:
-a Lists the available sleep states on the computer
-d [guid] Deletes the power plan specified by the globally unique identifier (GUID)
-h Toggles the hibernate feature on or off
-l Lists the power plans configured on a computer by name and GUID
-q [guid] Lists the contents of the power plan specified by the GUID
-s [guid] Makes the power plan specified by the GUID the active power plan
-setabsentia [guid] Makes the power plan specified by the GUID the power plan to use when no one is logged on
By default, Windows Vista computers use hybrid sleep instead of hibernate. Hibernate should not be configured without first determining compatibility.
The following is a sample listing returned by typing powercfg–l at a command prompt:
Existing Power Schemes (* Active)-----------------------------------Power Scheme GUID: 381b4222-f694-41f0-9685-ff5bb260df2e (Balanced)Power Scheme GUID: 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c (High performance)Power Scheme GUID: a1841308-3541-4fab-bc81-f71556f20b4a (Power saver)Power Scheme GUID: c1d97820-3148-42a9-a587-75d618a9bb2b (Graphics Department Plan) *
The active plan is marked with an asterisk. From this listing, you can determine that a computer has four power plans and the active power plan is the Graphics Department Plan.
If you want to configure power plans or modify power settings using powercfg, you'll need to do this using an elevated command prompt. When a parameter requires a GUID, the easiest way to obtain this value is to type powercfg–l at an elevated command prompt and then copy the value for the appropriate power plan. For example, if you wanted to make the Balanced plan the default for the computer in the previous example, you would type the following at an elevated command prompt:
powercfg -s 381b4222-f694-41f0-9685-ff5bb260df2e
In Group Policy, you'll find policy settings for managing power plans under Computer Configuration\Administrative Templates\System\Power Management. Under Notification Settings, you'll find policy settings that enable you to configure low battery and critical battery alarm actions. Under Button Settings, Hard Disk Settings, Processor Settings, Sleep Settings, and Video And Display Settings, you'll find separate policy settings for when the computer is plugged in and when the computer is running on battery power. To apply a policy setting, enable the policy and then select the appropriate action.
Through Group Policy, you can also specify an active power plan. How you work with Power Management policies depends on whether you want to use a default power plan, an updated preferred plan, or a custom power plan that you've created. If you want all computers that process a particular policy to use one of Windows Vista's default power plans, follow these steps:
After you open the Group Policy object that you want to work with for editing, expand Computer Configuration\Administrative Templates\System\Power Management.
Double-click Select An Active Power Plan.
Select Enabled and then use the Active Power Plan list to select the plan to use. The options are High Performance, Power Saver, and Automatic. If you choose Automatic, Windows Vista uses the Balanced power plan in most cases.
Click OK.
If you want all computers that process a particular policy to use an updated preferred plan or a custom power plan that you've created, follow these steps:
Double-click Select A Custom Active Power Plan.
Select Enabled and then in the Custom Active Power Plan (GUID) text box, type the GUID of the power plan to use.
To determine the GUID of a power plan, get a list of the power plans configured on a computer by typing powercfg −l at an elevated command prompt.
Alarms determine whether a laptop sounds an alarm or displays a warning message when its battery reaches a certain level. You can configure two levels of alarms for laptops: Low Battery Alarm and Critical Battery Alarm. The Low Battery Alarm is meant to alert the user when the battery power level is nearly depleted. The low-power state is activated by default when the battery has 10 percent or less power remaining. The Critical Battery Alarm is meant to alert the user when the battery is about to fail. The critical-power state is activated by default when the battery has 3 percent or less power remaining. On a battery with a three-hour life, 3 percentage points is about 5 minutes of usage.
An alarm action associated with each alarm enables you to dictate what specific actions the operating system should take when an alarm level is reached. You can also configure the computer to run a program when an alarm occurs. This is useful if you need to run a cleanup script or another program that helps maintain the system and the user's data. Because there are different considerations for configuring the alert levels, I'll examine each separately in the sections that follow.
As stated previously, the low battery notification is a warning that the system is getting low on power. When entering the low-power state, the system notifies the user with either a text prompt alone or a text prompt and an audible alarm. In some cases, you might want to configure the computer to go a step further and enter standby mode in addition to or instead of giving a warning.
To configure the low battery notification and actions, follow these steps:
After you open the Group Policy object that you want to work with for editing, expand Computer Configuration\Administrative Templates\System\Power Management\Notification Settings.
To set the low battery notification action, double-click Low Battery Notification Action. Select Enabled and then use the Low Battery Notification Action list to select the desired action, such as Sleep. Click OK.
To specify when the low battery alarm is triggered, double-click Low Battery Notification Level. Select Enabled and then use the Low Battery Notification Level combo box to set the appropriate alarm level. Click OK.
The default low battery alarm level is based on the total battery life and is 10 percent. On most systems, this is an appropriate value. However, I've found that on some systems, especially those with poor batteries, this isn't enough, and then I increase the level to between 12 and 15 percent. In contrast, on energy-efficient systems or those with two batteries, the default value is often too much. Here, I adjust the level so that the user is notified when about 20 minutes of battery power remains.
By default, users are notified when a computer's battery runs low. If you want to disable user notification for a low battery condition, double-click Turn Off Low Battery User Notification, click Enabled, and then click OK.
Critical battery alarms are designed to ensure that systems enter an appropriate mode prior to running out of power. When entering a critical-power state, the system notifies the user and then enters sleep mode. In sleep mode, the computer's power-manageable components shut off to conserve power. I often configure the low-power alarm so that the computer enters sleep mode. I then configure the critical-power alarm to have the computer enter hibernation mode or shut down. This takes power management to the next level and helps preserve the system before power is completely exhausted.
To configure the critical battery actions, follow these steps:
To set the critical battery notification action, double-click Critical Battery Notification Action. Select Enabled and then use the Critical Battery Notification Action list to select the desired action, such as Hibernate or Shut Down. Click OK.
To specify when the critical battery alarm is triggered, double-click Critical Battery Notification Level. Select Enabled and then use the Critical Battery Notification Level combo box to set the appropriate alarm level. Click OK.
The default critical alarm level is based on the total battery life and is 3 percent. In most cases, this value is appropriate. However, if you plan for the computer go into hibernation or shut down, you might want to reduce this value. You also want to take into account the battery life. If a computer has a long battery life, the default typically is too high, but if a computer has a short battery life, it might not be high enough. I usually set the critical power alarm so that the alarm action is triggered when there are 6 to 8 minutes of power remaining.
