Trying to consume less energy in a home office by putting workstations to sleep automatically seemed like the right thing to do.
But when two Windows 7 PCs developed insomnia, returning them to a greener state let me discover some interesting tricks and tips.
It started about five months ago. I looked at what we contributed annually to the local utility company and was not pleased. It was time to look at ways to cut our power consumption.
The first stepwas to calculate how much power we were actually using, in real numbers. To that end, I purchased a Kill a Watt device (info page), which tests and tracks the amount of energy computers and other household appliances use. Costing less than U.S. $30, this small box sits between an electrical device’s power plug and your wall outlet.
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I discovered that, on average, I spent about $200 a year just to power my office PC, monitor, and printer if I leave them on all the time. Enough to make researching energy-saving techniques worthwhile.
However, simply turning those devices off was not the perfect solution. Sometimes I’m out of my office and need to access my workstation PC. Rather than leave it on, I want it to wake up when I sign in remotely.
This capability is called Wake-on-LAN (WOL) — a technology found in most of today’s network cards and a key component to my energy-saving plans.
To determine whether your PC supports WOL, click Settings, Control Panel, and then Network Connections (or the Network and Sharing Center in Win7). Click Local Area Connection, Properties, and then Configure (near the box listing the network card name). There should be a Power Management tab; if so, look for a checkbox labeled Allow this device to wake the computer or something similar. (See Figure 1.) Checking the box should ensure that a received Wake-on-LAN network packet will power up the computer.
Figure 1. Check for Wake-on-LAN capabilities in your network card’s configuration settings.
Home Server wakes up your office network
Controlling when PCs wake up and go to sleep gets complicated when you want to remotely sign into more than one system on your network. One solution is a good remote-access application such as logmein.com. My solution was to purchase an HP server with Windows Home Server (WHS) installed. An accessory app, Wake on LAN Add-in for WHS (download page), lets me remotely access the server and use it to wake up the workstations; it costs U.S. $20.
While the wake-up part was relatively easy, getting the PCs to consistently and automatically go back to sleep proved far more challenging — nearly impossible, in fact — which was surprising, given Win7’s enhanced power-management controls.
According to the advice on many Web sites, disabling the network card’s Wake-on-LAN control is the best way to ensure a PC goes to sleep automatically — good advice for a simple home PC setup. But since I needed Wake-on-LAN for remote access and so that Windows Home Server could automatically back up my workstations each night, that trick was out.
I’ve also found that using USB devices can make the computer suddenly stop dropping into sleep mode even after going to sleep for weeks. My fix is to either reboot the system or manually put it to sleep.
When any PC’s automatic-sleep mode proves unreliable, my first step is to confirm that the BIOS is up-to-date. (Surprisingly, I’ve had to flash the BIOS on Vista and Win7 systems more often than on any preceding OS.) I next check that the network adapter drivers are current.
In the case of my Windows 7 machines, the last stop was the PCs’ power-management settings, where I selected the Power Saver option.
I also applied the hotfix described in Microsoft Support article 981112, which may fix a known sleep-mode problem — sleep mode and hibernation fail when you have Windows Media Player is installed and media-sharing is not turned on. (There’s a hotfix I didn’t need, but you might if you’re running Win7 and have a biometric device attached. According to MS Support article 975599, you could receive a system Stop error when you try to put the machine into sleep or hibernation.)
Discover what sleep modes your PC uses
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:
- S1 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.
- S2 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.
- S3 maintains just enough power to keep the information in RAM from being lost. Standby takes a bit longer to restart than does Sleep.
- S4 (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.)
Launch the Command Prompt window as described above. Type in powercfg /energy and let the system run the test for 60 seconds. (See Figure 2.)
Figure 2. You can generate a report of your Win7’s energy use with a Command Prompt control.
Look for the test results in a file called energy-report.html, located in the c:Windowssystem32 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.
Figure 3. Windows 7’s “energy-report.htmlText report” can tell you why your PC will not go into sleep mode.
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.
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Susan Bradley recently received an MVP (Most Valuable Professional) award from Microsoft for her knowledge in the areas of Small Business Server and network security. She’s also a partner in a California CPA firm and writes the Windows Secrets Patch Watch column.