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PC Energy Savings Guideline

UH has over 10,000 networked personal computers to support teaching, research and administration. PCs and other electronic office equipment, such as printers and scanners, collectively consume significant amounts of energy. Fortunately, there are ways that personal computers users can conserve energy and save money, without major impact to operations.

A desktop personal computer with LCD monitor uses about 1080 kWh per year if left on 24/7 and would cost UH $225* to run. (*Energy rates are expected to increase.) Turning off the computer when you leave for the day, would save about 65%. UH could save $1.57 million a year in energy costs (based on 10,000 units at $0.23 per kWh). Energy estimates depend on computer specifications, duration of use, as well as type of use.

Factors that Affect Energy Use

(adapted from Saving Energy, http://michaelbluejay.com/electricity/computers.html)
 

More Energy   Less Energy
Ready to be used  Sleep / Standby
Desktop      Laptop
CRT monitor LCD (flat panel display)
Faster processor    Slower processor
Older processor (Pentium, G3/G4/G5) Newer processor (Core Duo)
PC    Mac
Heavy use Light use
(processor-intensive task) (e.g. email, word processing)
On the Internet  Offline

 

Modern computers are designed with energy-saving components and come with advanced power management. Power management, standard in Windows and Mac operating systems, can put inactive monitors and computer systems (CPU, hard drive, etc.) into low-power "sleep" mode. Moving the mouse or touching the keyboard "wakes" up the monitor and computer in seconds. Power saving settings can be adjusted to meet your needs.

A desktop computer when shut down uses 3-5 watts; when it is idle, it uses an average of 89 watts. A laptop computer when shut down uses 3 watts; when it is idle, it uses 15-25 watts.* By putting your computer to sleep when it's inactive, considerable energy savings can be realized.

*from Dell on Dell: Energy Efficiency

Recommendations for PC Energy Savings
  •  Turn off computers when you are done for the day.*


*Exceptions: if software updates and backups are done after work hours, consult with your departmental IT staff. Leave your computer on if you need to access it remotely.

  • Set power management options to automatically put your computer to sleep/standby mode after 15 minutes or less of inactivity.*


* If nothing else, set power management for monitors. Set hard drive power management after consulting with your departmental IT staff as applications may be affected.


   Recommendations for Power Management
   (adapted from MIT for use at UH, http://web.mit.edu/ist/initiatives/it-energy/guidelines.html)

   Configuring Power Management for Personal Computers http://www.hawaii.edu/askus/926


   WINDOWS XP (Start > Control Panel > Power Options)

   Desktop Computers:
   Monitor - turn off after 10 minutes of inactivity
   Hard disk - turn off after 5 minutes of inactivity
   System standby - after 1 hour of inactivity
   System hibernation - never

   Laptop Computers (plugged in):
   Turn off monitor - after 10 mins
   Turn off hard disks - after 20 mins
   System standby - after 1 hour
   System hibernates - never

   Laptop Computers (on battery):
   Turn off monitor - after 5 mins
   Turn off hard disks - after 10 mins
   System standby - after 1 hour
   System hibernates - after 2 hours

   WINDOWS VISTA (Start > Control Panel > System and Maintenance > Power Options)

   Desktop Computers:
   Monitor - turn off after 10 minutes of inactivity
   Hard disk - turn off after 5 minutes of inactivity
   System standby - after 1 hour of inactivity
   System hibernation - never

   Laptop Computers (on battery):
   Display - turn off after 5 minutes of inactivity
   Put computer to sleep - after 15 minutes of inactivity

   Hard disk - turn off after 5 minutes of inactivity
  
   Laptop Computers (plugged in):
   Display - turn off after 10 minutes of inactivity
   Put computer to sleep - after 1 hour of inactivity

   Hard disk - turn off after 20 minutes of inactivity
  
   MAC OS (System Preferences > Energy Saver)

  
Desktop Computers:
   Put the computer to sleep when it is inactive for: 1 hour
   Put the display to sleep when it is inactive for: 15 minutes
   Do not check the box for "Put the hard disk to sleep when possible"

   Laptop Computers (on power adapter):
   Put the computer to sleep when it is inactive for: 1 hour
   Put the display to sleep when the computer is inactive for: 15 minutes
   Do not check the box for "Put the hard disk to sleep when possible"  

   Laptop Computers (on battery):
   Put the computer to sleep when it is inactive for: 15 minutes
   Put the display to sleep when the computer is inactive for: 5 minutes
   Check the box for "Put the hard disk to sleep when possible"

  • Avoid using screen savers.

They waste energy and do not save the screen. A screen saver requires that the PC and monitor be at full power. Some graphics-intensive screen savers may burn twice as much energy. Screen savers may prevent the computer from entering sleep mode. You only save energy if the monitor goes dark by going to sleep. Modern CRT and LCD screens are not prone to "burn in" from phosphor burn as older monitors.

  • For desktop computers, use LCDs instead of CRT monitors.

LCDs use less energy (30-35 watts) than CRT monitors (80 watts).

  • Use a laptop computer, if possible. They are more energy-efficient than desktop computers.

A desktop computer when idle uses an average of 89 watts. A laptop when idle uses 15-25 watts. (Dell on Dell: Energy Efficiency)

Please consider your work requirements and budget when purchasing computers. Laptops cost more, have less expansion/upgrade options, and are more prone to theft/security issues than desktop computers.

  • Purchase Energy Star-rated computers when possible.

Energy Star is a joint program of the US Environmental Protection Agency and the Department of Energy to help us save money and protect the environment through energy efficient products and practices. From July 20, 2007, Energy Star's new specifications for computers went into effect. Only the most energy-efficient computers will qualify for the Energy Star label.

   http://www.energystar.gov/index.cfm?fuseaction=find_a_product.showProductGroup&pgw_code=CO

FAQ

(adapted from http://www.energystar.gov/index.cfm?c=power_mgt.pr_power_mgt_faq)

 

1. Why should I use power management features?

You can save up to $75 or more per computer by activating system standby or sleep mode features. You save energy, reduce carbon dioxide emissions and help prevent global warming.

2. My screen saver is activated. Do I need to activate power management features?

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 time after which the monitor enters sleep mode. If your screen saver appears but your monitor never enters sleep mode, your screen saver may be the culprit: try disabling it.

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

In reality, 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.

4. Can sleep features wear out hardware by forcing the computer to turn on and off several times a day?

"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."

 

Technical Considerations
  • Your computer will not go to sleep mode if programs are running in the background.

  • If your computer is too old (> 5 years old), it may not have power management capabilities.

  • If you run special applications which require the computer not to be in sleep mode, please do NOT turn on power management for the hard drive.

  • See case studies of businesses, universities and schools that have activated system standby.
    http://www.energystar.gov/index.cfm?c=power_mgt.pr_power_mgt_ss#uwi

 

Software

Edison for Windows, free for individuals to manage their own PC, free from Verdiem for Windows 2000/XP/Vista/7
Edison for Windows

EZ Wizard tool for individuals to manage their own PC, free from EPA, for Windows 2000 and XP
http://www.energystar.gov/index.cfm?c=power_mgt.pr_power_mgt_ez_wiz

EZ GPO network management tool for system/network administrators to centrally manage computers, free from EPA
http://www.energystar.gov/index.cfm?c=power_mgt.pr_power_mgt_ez_gpo

Resources

Energy Star
http://www.energystar.gov/

MIT
http://web.mit.edu/ist/initiatives/it-energy/guidelines.html

Ohio State University
http://www.ohio.edu/sustainability/greenpc/

Microsoft
http://www.microsoft.com/whdc/archive/winpowmgmt.mspx

Saving Electricity
http://michaelbluejay.com/electricity/computers.html

Climate Savers
http://www.climatesaverscomputing.org/learn/energy-saver-guide/

Save and Go Green: Computer Energy Saving
http://www.paystolivegreen.com/2008/08/save-and-go-green-computer-energy-saving/

10 Computer Energy Saving Tips: Go Green
http://computers.toptenreviews.com/economy/10-computer-energy-saving-tips-go-green.htm

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Article ID: 925
Created: Thu, 17 Jul 2008 2:26pm
Modified: Thu, 10 Nov 2011 9:13am