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PC power management refers to software-based mechanisms for controlling the power use of Personal computer hardware. This is typically achieved through software that puts the hardware into the lowest power demand state available, making it an aspect of Green computing.

A typical office PC uses about 90 watts when active (approximately 50 watts for the base unit, and 40 watts for a typical LCD screen); and three to four watts when ‘asleep’. Up to 10% of a modern office’s electricity demand can be due to PCs and monitors.

While most PCs allow low power settings, there are frequently situations, especially in a networked environment, where processes running on the computer will prevent the low power settings from taking effect. This can have a dramatic effect on energy use that is invisible to the user. Operational testing has shown that on any given day an average of over 50% of an organization's computers will fail to go to sleep, and over long periods of time this affects over 90% of machines. This leads to most computers having the option of customizing power management systems and has created a market for third-party power management software to further control a computer’s power use.

Windows 'Insomnia' (Sleepless PCs)

The Windows power management system is based upon an idle timer. If the computer is idle for longer than the pre-set time, then the PC may be configured to sleep or 'hibernate'. Windows uses a combination of user activity and CPU activity to determine when the computer is idle.

Applications can temporarily inhibit this timer by using the 'SetThreadExecutionState' API. There are legitimate reasons why this may be necessary such as burning a DVD or playing a video. However, in many cases applications can unnecessarily prevent power management from working. This is commonly known as Windows 'Insomnia' and can be a significant barrier to successfully implementing power management.

Common causes of this so-called 'insomnia' include:

• Legacy or non-power management aware applications
• Open file handles on remote computers
• Faulty mice which can cause cursor movement even though the user is not present. (This makes the operating system believe that a user is present.)
• Scheduled maintenance tasks causing significant CPU activity
• High network activity

Software solutions

Operating systems have built-in settings to control power use. Microsoft Windows supports predefined power plans and custom sleep and hibernation settings through a Control Panel Power Options applet. Apple's macOS includes idle and sleep configuration settings through the Energy Saver System Preferences applet. Likewise, Linux distributions include a variety of power management settings and tools.

There is a significant market in third-party PC power management software offering features beyond those present in the Windows operating system. Notable vendors include 1E's 'NightWatchman', Data Synergy's 'PowerMAN', Faronics' 'Power Save', Verdiem's 'SURVEYOR'.

Some studies have suggested that power management tools can save on average 200 kg of CO₂ emissions per PC per year and generate $36 per PC per year in energy savings. This makes power management software an attractive option for large companies.

See also

• IT energy management
• Advanced Configuration and Power Interface

References

1. ^ Sleepless of Seattle; Why Windows Power Management Doesn't Always Work, Mark Blackburn, Strategy Analyst, 1E, January 2009.
2. "SetThreadExecutionState Function". Microsoft. Retrieved 7 June 2010.
3. "Windows 10 help". Microsoft. Retrieved 9 April 2015.
4. "Use the Energy Saver settings on your Mac". Apple. Retrieved 9 April 2015.
5. "Power management". ArchLinux. Retrieved 9 April 2015.
6. "Power Management Software for Windows Workstations". Archived from the original on 5 December 2010. Retrieved 23 September 2010.
7. "Energy Star Commercial Packages List".
8. The Headmasters' and Headmistresses' Conference. "HMC: A Practical Guide to Sustainable Building for Schools". Archived from the original on 15 March 2012.
9. "PC Power Management Solutions". 26 May 2009.
10. "University of Oxford Low Carbon Project: Energy and the networked computing environment".
11. Bisetty, Krisendra (29 April 2008). "Powering down and ramping up" (PDF). Business in Vancouver. Vancouver, BC, Canada. p. B3. Archived from the original (print) on 6 January 2010. Retrieved 28 March 2014.
12. Francis, Russ (29 September 2005). "B.C. Hydro adds energy-efficient software to online catalogue". ITBusiness.ca.
13. "How Dell Does IT: Energy Efficiency, Dell Cuts energy costs by up to 40% with a new power management plan". Retrieved 27 June 2009.
14. "OK Computer: EMA in Practice - article, The Environmentalist, Issue 77, 5 May 2009, Institute of Environmental Management and Assessment".

• Personal computers
• Sustainable technologies
• Computers and the environment
• Power supplies