Windows 8 has built-in utility called PowerCfg; when troubleshooting sleep problems, I find its little-known switch -Energy invaluable.
Topics for Windows 8 PowerCfg -Energy
- Using PowerShell to Run PowerCfg -Energy
- Examining the Energy-report.html
- PowerCfg -Energy Analysis Results
- Troubleshooting Sleep Problems with PowerCfg
Guy’s Rule for Laptops Notebooks and Tablets
Every mobile computer exhibits at least one of these Power Management issues.
- Won’t awaken up from sleep or hibernation.
- Suddenly wakes up for no apparent reason.
- Refuses your attempt to set: Sleep, Hibernate or Standby.
- Battery life does not come close to manufacturer's claim.
The old-fashioned way was to run built-in Windows utilities is by launching a 'DOS box' with cmd.exe; the modern way is execute all command-line programs through PowerShell. PowerCfg with PowerShell seems particularly apt.
Here is an example:
PS C:\WINDOWS\system32> PowerCfg -Energy
Enabling tracing for 60 seconds…
Observing system behavior…
Analyzing trace data…
Energy efficiency problems were found.
Note 1: When you run the command, scroll down to the bottom, observe a note saying:
See C:\WINDOWS\system32\energy-report.html for more details.
Note 2: The energy-report.html file is created in the current directory, and not necessarily in the \windows\system32 folder.
Encouraging computers to sleep when they’re not in use is a great idea – until you are away from your desk and need a file on that remote sleeping machine!
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Here are more details about sleep from the resultant energy-report.html.
Platform Power Management Capabilities:
Supported Sleep States
Sleep states allow the computer to enter low-power modes after a period of inactivity. The S3 sleep state is the default sleep, and only consumes only enough power to preserve memory contents and allow the computer to resume working quickly.
S1 Sleep Supported true
S2 Sleep Supported false
S3 Sleep Supported true (Sleep)
S4 Sleep Supported true (Called Hibernate)
Very few platforms support the S1 or S2 Sleep states.
The energy-report.html is even color coded. Here is an example of a service that is preventing your computer from sleeping.
System Availability Requests:System Required Request
The service has made a request to prevent the system from automatically entering sleep.
Requesting Service defragsvc (Defrag)
This warning could explain why the battery life is shorter than advertised.
Power Policy:Disk timeout is long (Plugged In)
The disk is configured to turn off after longer than 30 minutes.
Timeout (seconds) 1860
Note 3: When working with PowerCfg I like to have the Device Manager open so that I can check the 'Power Management' tab of the mouse, keyboard and other devices that could bring the computer out of its slumber.
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- I find PowerCfg quicker to use troubleshooting than the Control Panel’s Power Management GUI.
- This utility can also be used in Windows 7, but not Server 2008.
- The report reveals vital information on which devices are supposed to wake the computer.
- PowerCfg helps you to understand the inter-relationship between the sleep components.
- Experiment with PowerCfg led me to investigate group policies that were controlling sleep settings.
Computer Configuration\System\Power Management. (See screenshot right)
Researching More Switches with PowerCfg /?
For troubleshooting power-related problems there are several other useful switches to see the full list try: PowerCfg /?
/LASTWAKE Reports what woke the system from the last sleep.
/WAKETIMERS Enumerates active wake timers.
/BATTERYREPORT Generates a report of battery usage.
Note 4: As with many command-line utilities you could use the /forward slash instead of the -dash. Incidentally, the help file shows the /, where as most people perfer the -dash as used with PowerShell's parameters.
Refining PowerCfg -Energy
Research other switches reveals that -Energy itself has modifies such as -Trace and -XML (creates energy-report.xml instead of .html). There is also a -Duration to adjust the time it takes to analyze your computer's settings.
Example of a Battery Report
Battery ID Sony Corp.
Manufacturer Sony Corp.
Long Term 1
Design Capacity 57720
Last Full Charge 57720
Sleep Mode v Hibernate
When you close a laptop's lid the operating system cuts the power to all unneeded parts of the machine, thus conserving power. In this sleeping mode, there is a trickle of power to the RAM so that it can restart the disk and monitor when a user presses a key. (S3 mode in BIOS)
In the case of hibernation, the disks have to spin-up and the operating system must read the hiberfil.sys file, hence you can detect an appreciable delay before the machine is ready to accept user input. (S4 mode in BIOS)
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Here are ideas to troubleshoot common sleep or premature awakening problems using PowerCfg and its switches.
Problem 1: Access Denied
The most common problem is access denied despite being and administrator, and using 'Run as Administrator'.
Solution 1a: Create another Administrator, logon as that account.
Solution 1b: Run scannow /sfc the PowerCfg.exe maybe corrupted.
Problem 2: Windows 8 Won't Sleep
This /Requests switch will display what's blocking sleep. Once you have identified the component try:
PowerCfg /Requestsoverride Driver "Legacy xyz" System
Problem 3: Computer Wakes Randomly
Solution 3 and 3a:
# Also remove the # and try:
# PowerCfg /DEVICEQUERY wake_armed
Problem 4: Could not open the NT Kernel Logger
I once had a message saying that PowerCfg could not run, because the logger was already running.
Solution 4: Close Performance Monitor.
Summary of Windows 8 PowerCfg -Energy
Windows 8's PowerCfg has a useful switch called -Energy. This technique is invaluable for troubleshooting sleep problems, particularly on Windows laptop or notebook or tablet mobile computers.
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