You may have noticed that after installing Windows 7 on your portable computer, it will no longer automatically wake from sleep for scheduled events such as:

  • Windows Updates
  • A scheduled TV recording in Media Center
  • Scheduled backups, defrag, etc.

This is because starting with Windows 7, the default power management behavior for notebooks is to not automatically wake up the system for an scheduled event or task.  This was done to preserve battery life by not having the notebook wake up during an inopportune or unexpected time for a scheduled event while on battery.

This behavior can be changed to enable wake timers using either of the following methods:

  1. Under Control Panel->Power Options->Change Plan Settings->Change Advanced Power Settings->Sleep->Allow Wake Timers, set both On Battery and Plugged In to ‘Enable’.
  2. From an elevated command prompt, use the PowerCfg.exe tool to change the power policy:
    1. powercfg -setacvalueindex SCHEME_CURRENT SUB_SLEEP bd3b718a-0680-4d9d-8ab2-e1d2b4ac806d 1
    2. powercfg -setdcvalueindex SCHEME_CURRENT SUB_SLEEP bd3b718a-0680-4d9d-8ab2-e1d2b4ac806d 1
    3. powercfg -setactive SCHEME_CURRENT

Note: #1 enables for AC power, #2 enables for DC (battery) power

For desktop computers running Windows 7, this is not an issue as the default value for the Allow Wake Timers setting is Enabled.