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Myth of the Month: Don't Turn Off Your PC


save energyThis is the second in our series of articles surrounding Energy Following the Productive User.  See the first here:How Energy Efficient Is Your Video Conferencing?

During the course of our customer interactions, we’ve run across a few IT professionals who still adamantly subscribe to the theory that you shouldn’t power your computers down when they aren’t in use. They claim that computers that are left on at all times last longer than those powered down.

According to User Guide to Power Management for PCs and Monitors", Bruce Nordman, Lawrence Berkeley National Laboratory, January, 1997, LBNL-39466

"The belief that frequent shutdowns are harmful persists from the days when hard disks did not automatically park their heads when shut off; frequent on-off cycling could damage such hard disks. Conventional wisdom, however, has not kept pace with the rapid technological change in the computer industry. Modern hard disks are not significantly affected by frequent shutdowns."


Though this may have been a problem in the early days of computers, it has long since ceased to be a realistic concern. In fact, According to the United States Department of Energy, there are no computers on the market today that last long enough to be negatively impacted by turning your computer on and off.

The following is a quote from Rocky Mountain Institute Home Energy Brief #7 Computers and Peripherals:

“Modern computers are designed to handle 40,000 on-off cycles before failure, and you're not likely to approach that number during the average computer's five- to seven-year life span. In fact, IBM and Hewlett Packard encourage their own employees to turn off idle computers, and some studies indicate it would require on-off cycling every five minutes to harm a hard drive."

To put this in perspective, if your computer is used every day for 5 years before you upgrade or retire that computer, you would have to turn it off and back on 21 TIMES PER DAY to reach 40,000 on-off cycles.

What It's Really Costing You

Turn it Off from Nigel Upchurch on Vimeo.

Now that you know that powering your computers off when they aren’t needed isn’t going to harm your equipment, let’s look at what leaving them on is costing your enterprise.

Each computer and monitor that is powered down when not in use (nights, weekends, vacations, and holidays) will save your company money. The chart below shows you just how much, based on an estimated power cost of $.12 kWh, your company could be saving in energy costs EVERY YEAR. In most parts of the world, the cost per kWh is much higher than $.12.

Number of PCs and Monitors  - Assuming One Year at $.12 kWh







 $         34.09

 $ 34,090.00





This doesn't include the amount of money that it is costing to leave on other office equipment, such as: printers, copiers, VoIP phones, video conferencing, thin clients, wireless access points, network switches, and distributed office servers.


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