Your Computer Needs Its Sleep

The Star Tribune's Fixit columnist, Karen Youso, has an upcoming article on "phantom load" -- the electrical power that is used by all the appliances in your house or office even when they're not turned on. I had emailed her a while back to ask about this, and just heard that she's got a story due to be published on April 19.

I've been wondering about this topic for a while. For instance, how much energy does a "sleeping" computer use vs. one that's turned off vs. one that's completely unplugged?

Karen was nice enough to send along a link to a study on standby power by Lawrence Berkeley Labs, which she used in writing her story. (This link goes to the study's data table, but be sure to click on the links on the left side of the page for more info.)

The frustrating thing about the Berkeley data is that the amount of power being used by different types of the same appliance varies pretty widely -- for instance, for desktop computers, the average draw while turned on was 73.97 watts, but one computer used as little as 27.5 and another as much as 180.83. Some computers used no power at all when off, while another used over 9 watts. In sleep mode, the average was 21.13, but one computer used 83.3 watts -- more than the average amount used by the desktop models when on!

And from the report, there's no way of knowing whether a specific model of a specific brand consistently delivers a certain power efficiency (say, a Mac vs. a bottom-of-the-barrel OEMed Windows box). A guy named Mr. Electricity says that in general, Macs use a bit less energy than PCs, laptops use less than desktops, and LCD monitors use way less than CRTs. The University of Pennsylvania has a chart that shows the draw for a range of Macs and PCs.

Of course, this isn't just (or even primarily) about computers. We've got lots of other appliances drawing power all the time, so much so that the Lawrence Berkeley folks report phantom load is estimated to use 5 - 10 percent of all electricity in the U.S.