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Save Energy at Your PC

Energy Scientists Propose Color-Coding Standard for PC Sleep Mode

June 1, 2005

Different computers use different indicator lights to signal that they are in energy-saving, or "sleep" mode. Users are often unsure if their PC is truly saving energy, rather than just turning its screen black. To reduce confusion, energy scientists proposed an industry standard, using green for "on," no light for "off," and amber for "sleep." Sleep mode can save up to $150 a year per computer.

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Science behind the news is funded by a generous grant from the NSF

BACKGROUND: After nine years of study, the Institute of Electrical and Electronic Engineers (IEEE) has published a new set of voluntary standards proposing a common set of names, colors and symbols for the power states of computers.

THE PROBLEM: Processing speeds for modern computers continue to increase rapidly, but it has also made the machines gluttons for electric power. And they rarely sleep: in a typical office, about two-thirds of computers operate on full power through the night. Leaving computers on constantly also increases heat gain, and hence the amount of cooling required, wasting even more energy. Many personal computers do feature an energy-efficient "sleep" mode, in which a computer shuts down disk drives, stops sending video signals to the monitor, and closes any idle circuits. But the terminology, symbols, and means of putting computers to sleep vary greatly among computer manufacturers, confusing the folks who buy and use them.

THE SOLUTION: The IEEE's proposed standard suggests three distinct states: on, off and sleep. An on-off switch with have a pictograph of a circle broken at the top by a vertical line; a sleep switch would have a crescent moon. Power lights should be steady green when the computer is at full operation, and amber during sleep mode.

BENEFITS: If adopted, the new standards could save consumers money on their electricity bills, and also spare them the confusion of figuring out the most energy-efficient model when purchasing a new computer. A typical desktop computer draws about 60 watts of power; a conventional CRT monitor adds another 50 watts. When in power-saving mode, however, a typical computer only draws about 5 watts. Over the course of a year, this translates into about $100 savings in electrical costs.

THE HUMAN FACTOR: When it comes to using the sleep mode, having an industry standard may not be all that keeps consumers form using sleep mode. Poorly written software, incompatible accessories, odd combinations of applications or other hitches can cause computers to freeze when powering up from sleep mode.

SCREENSAVERS: Approximately half the power of a personal computer is consumed by the monitor. Screensavers protect the monitor's screen, thus prolonging the life of the monitor, but they do not save on power.

IEEE-USA and the Human Factors and Ergonomics Society contributed to the information contained in the TV portion of this report.


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