Electrical power surges are unexpected, unwanted, and often uncontrollable. Power surges can wreak havoc with your expensive electronics unless you take steps to protect your property. Here’s what you need to know.

A power surge is a sudden, temporary increase in current or voltage. Normal voltage for residential use in the United States is 120 volts, with an acceptable range of 114 to 126 volts. If the voltage rises above this range, it can cause damage to appliances and equipment. A surge protector is designed to prevent a surge from destroying electronic devices.

Surge protectors send surplus voltage to ground. In other words, they try to stop the voltage from going over 120 volts. Surge protectors are not failsafe. One large surge can destroy the protector and you may not know that your equipment is no longer protected.

We strongly discourage buying a basic surge protector. We recommend, at the minimum, a power strip with a UL rating of 1449 and a good warranty, preferably one with an audible alarm.

If you choose a power strip with an indicator light, place it where the light is visible, and make sure it is lit every time you sit down at your computer or turn on the device you are protecting. If the light is out, your surge protector has done its job and has given its life to save whatever is plugged into it. NOW THAT THE LIGHT IS OUT, IT IS NO LONGER A SURGE PROTECTOR; it is an extension cord and needs to be replaced.

Why do surges occur?

The most familiar source of surges is lightning, though it is actually one of the least common causes. When lightning strikes near a power line, telephone line or coaxial cable, the electrical potential can be measured in millions of volts. If a surge is caused by a lightning strike it is likely that most surge protectors will be overpowered.

The first line of protection from a lightning strike is an effective ground on your house wiring. Adding quality surge protection before your electrical panel and then a surge protector for expensive equipment are the second and third lines of defense. Protecting your telephone lines and coaxial cable is also necessary.

Most household voltage fluctuations are caused by high-power electrical devices operating within the home. These appliances, such as air conditioners and refrigerators, cause energy dips that a UPS (uniform power supply) can protect against. Large appliances require a lot of energy to switch on and turn off components like compressors and motors. This switching creates sudden, brief demands for power, which upset the steady voltage flow in the electrical system. While these variations are nowhere near the intensity of a lightning surge, they can be severe enough to damage components immediately or gradually over time, and they occur regularly in most household electrical systems.