Save Money With Power Management

Windows provides several levels of power management, all designed to cut power usage during periods of inactivity. Here is a description of the various power options and our recommendations.

Windows comes with several pre-defined "power schemes" accessible via the Power Options item in the Control Panel (we'll describe Windows XP, though other versions are similar). Most of these recommendations are for desktop PCs rather than laptops; for the latter you can adjust the settings to be more aggressive to gain improved battery life. The options in Windows are:

  What It Does Recommendation
Turn off monitor Puts monitor in sleep mode For desktops, set long enough so the monitor does not constantly turn off and on, especially for CRT (tube) monitors. Try 20-30 minutes for an office PC.
Turn off hard disks Hard disk stops spinning Even more than monitors, you do not want the hard disk repeatedly spinning up and down during the day. Try a setting of 1-3 hours.
System standby Puts the system in sleep mode Sleep mode means the drives, monitor, and CPU turn off but the motherboard stays on and contents of memory (RAM) are maintained, for "instant wake up" capability. An office PC can usually be set to 2-3 hours without turning off during the workday. Once asleep, PCs usually cannot be backed up by an overnight tape backup.
System hibernates Contents of RAM are saved to disk and PC is turned off Pinnacle of power saving. Enables quicker boots, so may be useful instead of turning one's PC off at night (see below). Must be set longer than standby mode; however, if you plan to be gone for a long time (say, overnight) consider disabling standby mode and using hibernation instead. In hibernation, PCs cannot be backed up by an overnight tape backup.

Power Saving Notes

Note that options such as "turn off monitor" do not actually turn the monitor off...the monitor will enter a sleep mode where it uses a small amount of power to watch for a wakeup signal from the PC. During vacations or long periods consider turning the monitor off manually, or unplugging it, to achieve maximum power savings. Likewise, modern PCs do not fully shut down; most have a rocker switch on the back of the power supply that can be turned off to completely power down a computer.

Newer PCs often save more power than their older counterparts, despite having faster electronics. One reason is that as manufacturing improvements shrink chip sizes, a CPU needs less power to produce the equivalent speed. Also manufacturers such as AMD are designing some amazing power saving capabilities into their newer CPUs. In a few years flash memory-based drives should become more common, further lowering power usage.

Hibernation Notes

To allow hibernation in Windows XP, open the Power Options dialog, click the Hibernate tab, and check the "enable hibernation" box. You can also use the Advanced tab to change the power button on the front of the PC to cause it to hibernate instead of shutting down, saving bootup time. Some device drivers and programs do not like hibernation mode; in particular we know of a common CPU temperature monitoring program that sounds a false alarm after the system wakes up (closing the program and immediately starting it up again reveals the alarm was mistaken).

To manually hibernate one's PC once hiberation is enabled, click Start, then Turn Off Computer. When that dialog box appears, hold down the Shift key and watch the "Standby" option turn into "Hibernate."

To turn on a PC that is in hibernation mode, press the power button.

August 2007

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