Computer Protection for Those Powerless Moments

Devices that guard your computer and data in a blackout are worth the money -- even if you don't live in the Golden State

By Stephen H. Wildstrom

Computers like few things less than an abrupt loss of power. At best, the operating system is unable to do the cleanup work normally done during an orderly shutdown, which can be especially serious with Windows NT or 2000. At worst, loss of power while the computer is writing a file on your hard disk can lead to serious data corruption. With rolling blackouts becoming a way of life in California, and perhaps elsewhere soon, power protection for your computer has never been more important.

The best way to defend your PC against the vagaries of electric utilities is an uninterruptible power supply. Despite its name, a UPS isn't intended to keep your computer running come what may but to give it a chance to shut itself down properly when the power fails, avoiding damage or data loss. The better units also regulate power to protect against voltage spikes or sags and to filter out electronic noise in the power supply.

UPS systems come in three flavors. The simplest provide just 5 to 15 minutes of standby power, kicking in when line voltage drops below a trigger level (duration depends on capacity, load, and temperature). An optional data link to a PC can allow the computer to shut itself down in the event of power failure. The most sophisticated units run your equipment off batteries all the time, constantly recharging the batteries from line current. These provide the cleanest power and eliminate the risk of your equipment failing in the few milliseconds that elapse between when line power goes and the batteries can kick in on a standby unit. A middle-ground solution gives full-time power conditioning but keeps the batteries offline until the power fails.


  Liebert Corp., which is best known for industrial-strength power conditioning and cooling systems for computer rooms, offers UPS systems of all three types for home or office use through its Web site ( I tried a PowerSure Proactive, a power-conditioning offline unit. You plug the unit into the wall, fire it up, then plug in your computer and other equipment (up to the wattage limit) into the four standard, three-prong outlets on the back of the UPS.

My only complaint is Liebert doesn't provide a universal serial bus alternative to the old-fashioned serial cable that notifies the PC of a power failure. These days, a PC can have up to 128 USB connections (even though most don't have that many) while free serial ports are hard to come by. The PowerSure Proactive comes in three models, ranging from 210 watts for $119.35 to 420 watts for $250.80. The standby-only PowerSure Personal line ranges from $77.38 for a 180-watt model to $108.12 for 300 watts. The top-of-the-line Interactive series, which provides online battery power, ranges from $295.90 for 450 watts to $826.10 for a 1,600-watt monster.

Although the Liebert PowertSure was the only unit I actually tested, quality UPS gear is sold by a number of manufacturers, including American Power Conversion ( and Tripp Lite ( In an uncertain world, a UPS can provide cheap insurance for you computer and, most important, your data.

Wildstrom is Technology & You columnist for BusinessWeek. Follow his Flash Product Reviews, only on BW Online

Edited by Beth Belton

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