Some good info from the Symantec site: BJ
Whether caused by blackouts, faulty wiring, or a bolt of lightning shaking hands with your wires, power surges can be damaging - even deadly - to your computer. When the voltage on a power line running into your house exceeds the amount the line can handle, the electricity looks for other routes. Often it chooses the cord running into your computer or other appliances. Your computer is then overloaded with electricity -- zapping its memory or melting the components inside.
Preventative Options
Surge suppressors and uninterruptible power supplies (UPS) are two options for power surge protection. To use, simply plug them into the wall outlet. Your computer, modem, phone or other components then plug into the device. Both surge suppressors and UPSs have pros and cons, mainly regarding cost and efficacy.
Surge Suppressors
Surge suppressors are the basic form for protecting your computer against errant electricity. The suppressor maintains a constant flow of power to the computer, suppressing damaging voltage surges. The suppressor may operate by absorbing the surge, blocking the surge, or a combination of the two.
Surge suppressors are the less expensive choice for protection. But many of the surge suppressors available in retail stores are little more than a power strip. When browsing your choices, compare ratings. The $10 power strip probably won't adequately defend your $2,000 computer. A quality surge suppressor costs $25 - $50. Remember your initial investment, and spend as much as you think it's worth to protect.
Uninterruptible Power Supply (UPS)
UPSs go one step further than surge suppressors by preventing surges and keeping your computer running in the event of a power shortage so that you can shut it down properly, preventing damage and data loss. UPSs contain an internal battery that charges itself when there is power, in preparation for when there is not. When shopping for a UPS, it's important to choose one with the right VA (volt-ampere) rating for your equipment. The average desktop requires 200 - 300 VA.
There are two basic types of UPSs:
Standby UPS. In the event of an outage, the UPS switches to a battery that delivers full power. The battery is charged by electricity during normal operation. With this type of UPS, there's a millisecond lag during the switch between electricity and battery, but it usually doesn't affect the computer. The standby UPS provides the minimum level of surge suppression at an economical price.
Online UPS. This type of UPS eliminates the lag during switchover, maintaining power steadily. The online system also diverts a steady stream of electricity to charge its battery. The online UPS is considerably more expensive than the standby.
UPSs are an excellent way to protect your system against power surges. They are more expensive than good surge suppressors, starting around $75 - $100, but they offer better protection and more options.
Protecting Your Computer
When you begin searching for the right surge protection, remember that retail methods are not invincible. A higher end UPS will protect your computer against most of the surges home computer users encounter. But if your house is struck by lightning, there's probably little that any surge protector or UPS can do to buffer that voltage.
As you are browsing the different options, strengths, and costs available, check the specifications on the packages and see how the devices measure up on the following:
UL 1449 rating. This is the guarantee that the surge suppressor meets the specifications of Underwriters Laboratory. The suppressor should meet or exceed the UL 1449 rating. If it's not marked on the surge protector, look for another device.
Clamping voltage. This is the point at which the surge protector starts suppressing electricity. The lower the clamping voltage, the better the protection. Look for one with a clamping voltage of 400 volts or less.
Response time. This is the time it takes for the suppressor to act. For the best protection, look for a suppressor that provides a response time of less than 10 nanoseconds.
Energy dissipation. This is the amount of electricity a suppressor can absorb before it blows. A good suppressor can absorb around 200 to 400 joules before it fails and passes the surge to the electrical ground.
Three-way protection. This is the number of wires the surge suppressor protects. The cheaper suppressors guard against surges in only the current-carrying wires. For added protection, use a three-way protection suppressor, which protects from surges that come through the ground wire.
Extra jacks. Because strong power surges can follow any path to your PC, you need to be sure that all components are protected. Look for a model that has jacks for your phone and coaxial cable jacks if you have a cable modem.
Damage Control
In spite of good equipment and best intentions, calamity sometimes strikes. If you are prepared for it, you can minimize the impact a power surge has by backing up your computer. While you may not save your hard drive, you might save the information on it such as documents, spreadsheets, financial records, email, address book, calendar and other important data. Backing up your computer protects all the hours of work you've spent in front of it. While you can buy a new hard drive, you can't buy new account information or irreplaceable email.
