Those at Energy Star recommend that you turn your computer off at night, for maximum energy savings. “We are all about energy savings, and when you shut off your computer at night, you save the most energy,” says Craig Hershberg, program manager for office equipment and consumer electronics. “Every little bit helps. It all adds up.”

However, here are some consumer “myths” that are worth addressing:


  • Turning your PC off uses more energy than leaving it on. Not true. The small surge of power you use when turning it on—which varies per PC make and model—is still much smaller than the amount you use in keeping it on for lengthy periods.
  • Turning your PC on and off wears it out. A decade ago, there was something to this, but not today, say Hershberg and others. It used to be that PC hard disks did not automatically park their heads when shut off, and that frequent on/off cycling could damage the hard disks. Today’s PCs are designed to handle 40,000 on/off cycles before a failure, and that’s a number you likely won’t reach during the computer’s five-to-seven-year life span.


Lab tests done by Dell show that a PC running Microsoft Office Small Business 2007 uses 42.7 watts, McCall says. If it runs continuously at that rate for 365 days, at 7 cents per kilowatt-hour, the power consumption costs would be $26.18 for the PC and $45.99 for a regular monitor, for a total of $72.17 for the workstation.

Flat-panel monitors use less energy (22 watts when left on, 3.3 watts in “sleep” mode) than regular monitors (75 watts when left on, 5 watts in “sleep” mode), McCall says. So the same workstation with Microsoft Office running for a year would use $39.67 in power with a flat panel.