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Power Management Frequently Asked Questions

What is power management?

Power management is a process that allows monitors and computers (CPU, hard drive, etc.) to enter low-power states when sitting idle. The low power modes of inactive computers can involve reducing power consumption or spinning down the hard disk. Inactive monitors with enabled power management enter low-power modes by turning off monitor output. By simply hitting the keyboard or moving the mouse, the computer or monitors awakens from its low-power “sleep mode” in seconds.

Why should I use power management?

Easy money. Your organization can save up to $100 per computer by activating power management on both the monitor and computers.

How can I enable power management?

ENERGY STAR features — standard in Windows 95, 98, ME, 2000, and XP* and MacIntosh operating systems — place inactive computers (CPU, hard drive, etc.) and monitors into a low power sleep mode. The steps towards power management are:

I have my screen saver activated, do I need to activate power management?

Often including complex images and graphics, screen savers generally do not save energy. Screen savers were developed to prevent the permanent etching of a pattern on older monochrome monitors. Screen savers would prevent this by either blanking out the screen entirely or by displaying a constantly moving image. Modern display screens do not suffer so much from this problem so screen savers are used for entertainment. If you want to use your screen saver in conjunction with monitor power management, set the screen saver “wait time” to less than the period of inactivity before the monitor shuts off automatically. In addition, although an activated screen saver may not be “showing” on monitor display while the monitor is in a low-power sleep mode, screen savers do run in the background and certain complex screen savers have been known to not allow a computer (hard drive, CPU, etc.) to sleep and also cause the computers to use as much as twice the energy.

Do computers and monitors use more energy with power management activated due to power surges when cycling on and off?

Many believe that leaving lights, computers, and other appliances on uses less energy than turning them off and also makes them last longer. On the contrary, the small surge of power created when some devices are turned on is vastly smaller than the energy used by running the device when it is not needed. While it used to be the case that cycling appliances and lighting on and off drastically reduced their useful lifetimes, these problems have been largely overcome through better design.

From “Eleven Energy Myths: From Efficient Halogen Lights to Cleaning Refrigerator Coils”, Lawrence Berkeley National Labs

Does shutting off computers and monitors through power management harm computers?

“Modern computers are designed to handle 40,000 on-off cycles before failure, and you’re not likely to approach that number during the average computer’s five- to seven-year life span. In fact, IBM and Hewlett Packard encourage their own employees to turn off idle computers, and some studies indicate it would require on-off cycling every five minutes to harm a hard drive …”

(Source: Rocky Mountain Institute Home Energy Brief #7 Computers and Peripherals.)

Some users still are under the impression that shutting off your computer does more harm than good. Modern computers are designed to withstand frequent shut offs. Please see boxes below. “The belief that frequent shutdowns are harmful persists from the days when hard disks did not automatically park their heads when shut off; frequent on-off cycling could damage such hard disks. Conventional wisdom, however, has not kept pace with the rapid technological change in the computer industry. Modern hard disks are not significantly affected by frequent shutdowns.”

(Source: “User Guide to Power Management for PCs and Monitors”, Bruce Nordman, Lawrence Berkeley National Laboratory, January, 1997, LBNL-39466)

What are the ENERGY STAR requirements for computers and monitor power management capabilities?

Since 1994, EPA has defined ENERGY STAR specifications for computers and monitors that call for lower energy use and require that power management capabilities be enabled when shipped. ENERGY STAR-labeled computers are required to power down to 15 percent of their maximum power use. ENERGY STAR-labeled monitors are required to power down to 15 watts or less after 15 to 30 minutes of inactivity and down to 8 watts after 70 minutes of activity. A new ENERGY STAR specification for monitors that goes into effect on January 1, 2005 requires that the monitor only draw 4 watts or less in sleep mode. By January 1, 2006, the sleep mode is 2 watts or less. The new ENERGY STAR specification also includes specifications for active power use in monitors. Learn more about ENERGY STAR qualified computer monitors.

How can I tell if my computers or monitor is enabled for power management?

In Windows 95, 98, Millennium Edition, 2000, and XP users can check power management status directly through the control panel. Visit Enable Power Management Manually to see manual instructions on how to set these features. For the monitors, another way to tell is if the screen goes blank after a period of inactivity, monitor power management is enabled. For computers, the low hum of the hard drive will stop after a period of inactivity.

How can I tell if my monitor is in an energy-saving low-power mode? How long do I have to wait for my monitor to recover?

Some monitors signal low-power modes with an indicator light on their front. Newer monitors usually turn the power indicator light from green to amber when in a low-power mode. Monitor recovery time, which depends on monitor type, indicates the type of low-power mode. If recovery from the blank screen is instantaneous, the monitor is likely in the first power management mode, standby or sleep. If 10 seconds or so are required for recovery, the monitor is likely in the second, lower power, mode, suspend. Newer liquid crystal display monitors wake up even quicker, 1 to 2 seconds.

Does monitor power management affect receipt of e-mail or downloading of files from the Internet?

If monitor power management is enabled, the screen may go blank during long download sessions. However, this will not interrupt the download operation. Power management also does not affect receipt of e-mail, faxes, or phone calls.

Are computers and monitors with power management more expensive?

No. Computers and monitors with power management are not more expensive than equipment without power management capabilities.

What power management options are available for my Windows operating system?

The table below illustrates the different power management options in Windows.

  • Windows 95 allows the user to set periods of computer inactivity before the monitor enters standby (a first “sleep” mode that allows for quicker recovery), monitor turns off (a “suspend” mode that takes longer to recover) and hard drives turn off.
  • Windows 98 introduced system standby and eliminated the monitor standby setting. System standby allows the system devices, such as monitors and hard disks, to enter a low power state that allows for almost immediate recovery. Because standby does not save your desktop state to disk, a power failure while on standby can cause you to lose unsaved information.
  • Windows ME and Windows 2000 added the system hibernate feature, which saves everything in memory on disk, turns off the monitor and hard disk, and then turns off your computer. Upon reactivation, the desktop is restored exactly. It takes longer to bring your computer out of hibernation than out of standby.
  • Windows NT does not support ENERGY STAR power management features that can be activated through the Control Panel.


95 98 NT ME 2000 XP
Monitor Power Management
Turn Off Monitor Y Y N Y Y Y
Monitor Standby Y N N N N N
Computer Power Management
Turn off Hard Drives Y Y N Y Y Y
System Standby N Y N Y Y Y
System Hibernate N N N Y Y Y

The availability of these options depends on the compatibility of operating system (including APM/ACPI), BIOS, and processor hardware.

How can I save energy if power management is not possible on my monitor?

If power management is not possible, you can switch off the screen when not in use for prolonged periods. For conventional CRT-type screens, this will save about half of the power used by the computer. During non-use hours, such as nights and weekends, you can turn off both your monitor and your computer, which reduces energy use to near zero. Note that newer monitors have a separate wall socket for both the monitor and the computer, so both have to be turned off. In earlier computers, the monitor was usually connected to the computer’s power supply, so that the monitor was turned off when the computer was turned off. In addition, the switch on the front of the monitor may be only the standby power switch. Some monitors have their on/off switch on their back or side.

Take These Steps to Activate Power Management Organization Wide

Step 1: Estimate your savings and view case studies.

Step 2: Decide which is right for you: monitor only or both monitor and computer.

Step 3: Evaluate software options and choose a power management method.

Step 4: Inform employees with free educational materials.

Step 5: Activate power management. EPA provides free technical support.

Step 6: Earn public recognition through the Million Monitor Drive campaign.