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Published: Saturday, 6/25/2005

On-off debate is on-off again

Leave the computer on constantly. Modern electronics devices were made to run 24/7 without "burning out." Turning a computer on and off shortens the life of the monitor and electronic parts inside the box.

No, no, no. Turn if off when you're away for even a couple of hours. You'll save hundreds of dollars on electricity, and those on-off cycles won't shorten the life of a modern computer.

That debate has simmered for years, with conflicting advice and theories from amateurs and experts alike.

Everyone agrees that computers and monitors can gobble up plenty of electricity. Look at a typical personal computer with a 17-inch monitor. It's using about as much elecricity as four 40-watt light bulbs.

Many households have two or more computers. Offices may have hundreds. In addition to direct use of electricity, computers and monitors produce heat. Home and office air conditioning systems consume electricity in removing the heat.

I've always taken a middle-of-the-road approach.

When I'm working from a home office, for instance, the PC goes on around 6 a.m. and off around 11 p.m. after I make a final e-mail check. One home PC, however, ran almost constantly from 1995-2003 and never needed repairs. It got shut down every few weeks to clear junk from the random access memory (RAM) chips, and allow the diagnostic self-tests that occur during startup.

The debate dates to the early days of personal computers in the 1980s. Experts thought that excessive switching increased the stress on electronic components. Turn it on, and tiny parts and connections between parts expand as the system warms up. Turn it off, and the parts contract as the system cools down.

Some even compared it to the winter freeze-thaw cycles that crack highway pavement.

However, there was little scientific information available on the issue.

Computers and monitors have changed since then, and are among the most reliable of all devices. If a computer works the first day, it probably will run so long that you wish it would die so you have an excuse to buy a new one.

Scientific information on the on-or-off question is available. One good source is a review of the research done by Oregon State University


The results, in brief, conclude that you can save money on electricity without shortening a computer s life with this approach:

Turn your monitor off if you will be away for 15 to 30 minutes or longer. Shut down your computer at the end of the day, unless there s a good reason to keep it on.

What s the risk of doing so?

Consider, for example, the risk of damage to the hard disk drive, which is the most vulnerable component in most computers. An average computer could be turned on and off 4 times a day, 5 days a week for 20 years before the hard disk drive is likely to fail, the review stated.

Michael Woods is The Blade s science editor. His column on computers and technology appears each Saturday.

Contact him at: mwoods@theblade.com.

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