PC power management

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. 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 lowering power demand. This is commonly known as Windows 'Insomnia' and can be a barrier to successfully implementing power management. Common causes 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.