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Computer Power Awareness: Use It when You Need It

Most of us at SLAC need computers many hours of the day, but how often do you think about the energy to keep those bits of information flowing?

On a recent sample survey to determine what office equipment was present and powered on at SLAC, my colleague Rohendra Atapattu and I discovered that more than 70 percent of the roughly 400 desktop computers observed were powered on (not in sleep or hibernation) after working hours.

A desktop computer uses approximately 74 watts of electricity. So if the computer is left on continuously for a year, that equates to more than 648,000 watt-hours or 648 kilowatt-hours. So for each computer that is left on or does not have the capability to be put into sleep or hibernation mode, SLAC incurs a cost of $40 per year. If you consider that there are roughly 3,275 computers on site, the annual cost to operate 70 percent of them continuously is more than $91,000 (2,100,000 kilowatt-hours). If you consider that most office computers are idle for about 12 hours each weekday and 24 hours on weekend days, the annual savings could be $62,000 (1,400,000 kWh) or a CO2 reduction of about 315 metric tons.

On the same survey we also noticed that roughly 60 percent and an additional 15 percent of computer monitors were in sleep mode or fully on, respectively. Monitors powered on—even with screen savers—consume roughly 55 watts. Those in sleep mode consume about 1 watt (new flat panels). There are roughly 3,700 monitors at SLAC (on average 15 percent more monitors per workstation than computers). As with the computers, shutting computer monitors off when not used for those extended hours would save SLAC $10,000 (170,000 kWh) annually or a CO2 reduction of about 78 metric tons.

Additional money could be saved by turning the monitor off when you leave for lunch, meetings or other events. When you come back, just switch it back on and it instantly is viewable.

We are working with the Office of the Chief Information Officer on a plan to create groups of computers specially configured to optimize power consumption while still allowing the security updates to take place. More detailed information will be forthcoming.

You may also contact us, SLAC Facilities Energy Program Engineers Ted Schnipper and Rohendra Atapattu, on this issue or other energy savings ideas and suggestions. We encourage your input.

Oh by the way, please take a look at this short video. It should provide some interesting insight.

—Ted Schnipper
SLAC Today, May 10, 2011