About how to troubleshoot power plans in Windows 7

High performance

The High performance power plan maximizes the brightness level and can increase the computer's performance. The tradeoff is reduced battery life and more heat generation because of more power use by the CPU, by the LCD, and by devices. The CPU fan will run faster and more frequently. This power plan is great for the prompt response that you want for gaming or for video editing. Opportunity cost is a key issue with customers. The High performance power plan requires more power per transaction, increases heat generation, and puts increased demand on moving parts such as fans.

Advantages

• The display is brighter. (This is helpful for outside use.)

• The computer operates at a very high level of performance.

Disadvantages

• There is the potential for more heat generation.

• Processor performance is not optimized during short idle periods.

• The CPU fan spins up more frequently.

Balanced

The Balanced power plan scales the performance level to match the current workload. This plan provides an optimal tradeoff between power consumption and performance on mobile PCs and on desktops and is the default setting.

Power saver

The Power saver power plan saves power by reducing system performance and screen brightness.

Advantages

• Battery life increases because of reduced power level.

• Screen brightness is reduced automatically.

• The CPU and hardware are set to aggressively take advantage of downtime.

• A mobile PC or a desktop computer consumes less power and generates less heat.

Disadvantages

• Applications may run slower or start slower.

• The screen may not be bright enough for outside use.

PowerCFG

PowerCFG is a powerful command-line tool that helps in diagnosing power-management issues. Frequently, a user may prefer not to wake the computer by using the mouse or is not sure why a computer woke. You can disable and enable devices by using the PowerCFG tool. Or, you can use the Power Management tab in the properties of the device in Device Manager to select the Allow this device to wake the computer check box. Additionally, the PowerCFG tool can be scripted for domain use.

The following are the more common commands that can be used to identify sleep states and default settings:

• POWERCFG -L or POWERCFG -LIST
  
  Use this command first. This command lists all power plans in the current user's environment. The power plan that is listed with the asterisk (*) is the active power plan.

• POWERCFG -Q or POWERCFG -QUERY
  
  Use this command second. Then, you can determine the exact settings that are applied. This command lists the contents of the power plans. To redirect the listing to a file, use a command that resembles the following:

  Powercfg -Q >c:\test.txt

• POWERCFG -DEVICEQUERY wake_armed
  
  Use this command to determine the devices that are set so that the user can wake the computer.
  
  For a mobile PC, this command may show devices similar to the following:

  • Standard 101/102-Key

  • Microsoft Natural PS/2 Keyboard with HP QLB

  • Synaptics PS/2 Port TouchPad

  
  For a desktop computer, this command may show devices similar to the following:

  • HID-compliant mouse (002)

  • Broadcom NetXtreme Gigabit Ethernet

  • HID Keyboard Device (002)

For more information about the PowerCFG options, run the POWERCFG /? command. Or, visit the following Microsoft TechNet website:

Powercfg Command-Line Options

Tips for troubleshooting

The following are tips that you have to consider when you troubleshoot power plans in Windows 7:

• What is the purpose of the computer? Is this a mobile PC that experiences little high-end use? Is it a datacenter-class server that has mission-critical SQL installed? Or, is it something in between?

• Does the computer have the latest BIOS installed? This is important when you investigate power issues.

• What are the BIOS settings that are available? Examine the BIOS options. Frequently, a user may have changed settings that affect the operating system. OEMs may expose the _OSC ACPI method to enable an operating system to adjust BIOS settings. For example, the DC mode for a mobile PC may set the CPU performance P-STATE level. The operating system would be unable to change this if the BIOS vendor did not let the operating system take ownership of this resource. The OEM may also adjust the BIOS and hardware so that regulatory requirements are compliant with set standards. In these cases, changing the settings may not be an option. These settings may not even appear in the Power Management console.

• Have the default settings for the power plan changed? To determine this, use the POWERCFG -Q command. If the default settings are changed, reset the current power plan. Frequently, a user or the system administrator may adjust the power plans. Remember, Group Policy may be enforced; changing a power policy that is controlled by Group Policy lasts only until the user logs on again. An administrator may completely block changes, or items from the list may be removed from use. The administrator should be consulted on these issues, and you must connect as an administrator when you use Remote Desktop to make changes. The key point to remember is that not all power policies are appropriate to all users and to their specific equipment.

• Power plans can be customized by an administrator, by a power application, or by Group Policy. Check these items before you continue to troubleshoot. Before you start any diagnostics or restore the power plans by using the Restore default settings for this plan option, you should capture the current settings by using the POWERCFG –EXPORT command. You can also click Create a power plan and then adjust the customized plan settings. If the power plans become corrupted, you can restore the power plans to default settings. This action will overwrite all default schemes.
  
  To restore the power plans to default settings, follow these steps:

  1. Click Start.

  2. In the Search programs and files box, type cmd.

  3. Right-click CMD, and then click Run as administrator.

  4. At the command prompt, type powercfg -restoredefaultschemes, and then press ENTER.

  5. At the command prompt, type exit to exit the Command Prompt window.

  6. Restart the computer.

• Does the computer have an OEM-supplied power-management application that is installed? If this is the case, look for updates, or test by disabling it. Many times, the OEM may augment the power-management policies by customizing the policies for their specific device. Contact the manufacturer when the power-management application is not working correctly.

• Review Windows Update. The Windows Update service is a key item to review. Also, make sure that you search the Microsoft Knowledge Base for known issues. Windows Update may have updated drivers available that may be relevant to your current issue. Many times, updated drivers are listed in the "Optional" section of Windows Update.

Frequently asked questions

Q1: Why does my computer wake every day at 12:48 and then run a diagnostic tool?

A1: To determine why this occurs, use the -WAKETIMERS option to determine what is currently set. Scheduled tasks are one of the primary items that the -WAKETIMERS option will show. To use this option, run the following command:

POWERCFG -WAKETIMERSNote If your computer is from an OEM, the results of this command may resemble the following:

Timer set by process_name\Device\HarddiskVolume2\Windows\System32\svchost.exe expires at 12:48:06 AM on 9/15/2010.
Reason: Task Scheduler will execute '\OEM\OEM Assistant Application\First Boot' task.

Q2: How can I determine all the available sleep states?

A2: Use the -AVAILABLESLEEPSTATES option. To do this, run the following command:

POWERCFG –AVAILABLESLEEPSTATESExample 1

The following is an example of the sleep states on a mobile PC from an OEM:

The following sleep states are available on this system: Standby (S3) Hibernate Hybrid Sleep

The following sleep states are not available on this system:

Standby (S1)

The system firmware does not support this standby state.

Standby (S2)

The system firmware does not support this standby state.
Example 2

The following is an example of a case in which the sleep states are disabled. This example was created by removing the current video driver and by using the VGA driver. The VGA driver does not support sleep states and does not poll the device for supported sleep state support. Windows polls not only the driver but also the BIOS before it enables any sleep states.

The following sleep states are not available on this system:

Standby (S1)

The system firmware does not support this standby state.

An internal system component has disabled this standby state.

Standby (S2)

The system firmware does not support this standby state.

An internal system component has disabled this standby state.

Standby (S3)

An internal system component has disabled this standby state.

Hibernate

An internal system component has disabled hibernation.

Hybrid Sleep
Note Do not forget to check the Power Options item in Control Panel and in the computer's BIOS, because available sleep states can be enabled or disabled in these locations.

Q3: Why did the battery life on my mobile PC that has a VGA display decrease after I upgraded to Windows 7 from Windows XP?

A3: This is a common issue in which the display is using the default VGA driver. This driver is not optimized for the video card and will consume more power. To resolve this issue, update your video card driver.


Q4: Why can't I see some power-management settings?

A4: Windows 7 cannot display power-management settings that the computer does not support.


Q5: How can I determine whether Group Policy is in effect and is forcing or recommending a particular power plan?

A5: Use the Gpresult command. This command shows what power options are applied. For more information about the Gpresult command, visit the following Microsoft TechNet website:

GpresultThe power plan can also be configured by using policy preference. Additionally, tracing can be enabled to troubleshoot preference issues that are related to power options.


Q6: How can I set a power plan in place without a restart?

A6: Use the POWERCFG -SETACTIVE {GUID} command. For example, run a command that resembles the following:

POWERCFG -SETACTIVE 8c5e7fda-e8bf-4a96-9a85-a6e23a8c635cThen, run the POWERCFG /L command to view the change in real time. The following is an example of what you see when you run the POWERCFG /L command:

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)

Q7: My computer is running slow on the "Power saver" power plan, and the battery is draining faster than I expect. What can I do? Can I diagnose what is occurring?

A7: To diagnose the problem, create a power report. To do this, follow these steps:

1. Click Start.

2. n the Search programs and files box, Type cmd.

3. Right-click CMD, and then click Run as administrator.

4. At the command prompt, type powercfg -Energy -output c:\temp\energy.html, and then press ENTER.

5. In the Temp folder, open the Energy-report.html file. This report uses a 60-second run. However, the report time is configurable. Review this document for errors and warnings. The informational section provides a detail of the Power Policy plan and the computer's configuration during the test period.

The following example shows several ways to optimize battery life. The report provides the results that let you make informed decisions. You can work through each error and warning to help optimize the computer.

Power Efficiency Diagnostics Report
Computer Name computer_name
Scan Time date time
Scan Duration 60 seconds
System Manufacturer OEM_name
System Product Name product_name
BIOS Date date
BIOS Version version_number
OS Build build_number
Platform Role PlatformRoleMobile
Plugged In true
Process Count 72
Thread Count 742
Report GUID {GUID}
Analysis Results

Errors

• Power Policy: Dim timeout is disabled (On Battery)
  The display is not configured to automatically dim after a period of inactivity.

• Power Policy: 802.11 Radio Power Policy is Maximum Performance (On Battery)
  The current power policy for 802.11-compatible wireless network adapters is not configured to use low-power modes.

• Power Policy: Dim timeout is disabled (Plugged In)
  The display is not configured to automatically dim after a period of inactivity. Average Utilization (percent) 7.38

Warnings

• Power Policy: Disk timeout is long (On Battery)
  The disk is configured to turn off after longer than 30 minutes. Timeout (seconds) 2400

• Power Policy: Display timeout is long (Plugged In)
  The display is configured to turn off after longer than 10 minutes. Timeout (seconds) 900

• Power Policy: 802.11 Radio Power Policy is Maximum Performance (Plugged In)
  The current power policy for 802.11-compatible wireless network adapters is not configured to use low-power modes.