To test what sleep modes are enabled on your system, do the following:
In Win7, click Start, All Programs, and Accessories. Right-click Command Prompt and select Run as administrator. In the Command Prompt window, type powercfg -a and press the Return key.
There are six power modes, S0 (fully on) through S5 (fully off). Labels such as standby and sleep are used interchangeably by different vendors, so are not a precise guide to identifying the mode you’re using. To save power, you might use any of the following:
step 1: is closest to fully up and running — the PC simply powers down the hard drive and monitor. Hit a key, and the system is instantly ready for work.
step 2: is power standby mode — the PC is on and maintaining full power to the RAM, thus preserving your open applications and data, but the CPU is essentially inactive.
step 3: maintains just enough power to keep the information in RAM from being lost. Standby takes a bit longer to restart than does Sleep.
step 4: (Hibernate) saves the state of the computer system (running programs and applications to a file on your hard drive and then powers off. Because the PC’s state is saved on the hard drive, shutdown and restart take longer. But you’re using almost no power. (Modern PCs are almost never completely off.)
When my system fails to go to sleep, I run an energy report to let me know exactly what device is keeping the system awake. You can create the report with the following steps:
Launch the Command Prompt window as described above. Type in powercfg /energy and let the system run the test for 60 seconds.
Look for the test results in a file called energy-report.html, located in the c:\Windows\system32\ folder, and open it in a browser.
In that report, scroll down to the error section and you can see the sort of devices that are keeping your system from going to sleep. In my case it tends to be after I’ve connected USB devices (such as an iPhone or Zune) to my workstation. I have yet to figure out why it happens.
I have two techniques for forcing my errant PCs to sleep: I reboot the workstation (which is a pain), or I manually make the workstation go into sleep mode. There are three ways to do this in Win7, but the easiest is to hit the Windows key, click the right-arrow next to the Log off button, and select sleep mode. After that, automatic-sleep mode works as it should when I end my remote-access sessions.
I also fine-tuned my power requirements on the various Vista and Win7 computers, following these steps:
Click Start, Control Panel, and then Power Options. Choose Power Saver and customize the settings for the length of time you want the system to stay on after you’ve finished using the computer. Then go to the advanced power settings and select Hybrid Sleep. This mode of sleep ensures that I will not lose any documents I forgot to save.
You can see other custom settings as documented on the Windows 7 power-plan settings forum at Windows SevenForums.
For now, automatic-sleep mode is still so unreliable that I take the extra steps of forcing my computer into sleep even at the end of remote access. I’m hoping that the upcoming Windows 7 Service Pack 1 will help to solve my issues. Until then, the bother of sleeping is worth the power and cost savings I get.