Dear Science: Is a “whole-house” surge protector a good investment? -- Buck R.

Dear Buck: The short answer is a qualified “yes”. Here’s an example. My wife and I lived for about 15 years in a desert region that experienced relatively few thunderstorms. Our house happened to be located higher than almost all houses near it. The residence did not have a whole-house surge protector. During those 15 years, nearby lightning strikes caused electrical energy surges on the power lines serving the house. These surges damaged beyond repair a washing machine and a dishwasher. Both appliances were only about halfway through their normal service life. It cost approximately $1500 (total) to replace them. A whole-house surge protector that cost about $500 (installed) would likely have spared those appliances. Assuming the depreciated value of the appliances at the middle of their normal service life was about $750, the protector would have saved about ($750 - $500 =) $250. If the appliances had been new when the surges occurred, the protector would have saved us $1000. If the surge had been larger and all the appliances in the house were new, the protector could have saved us $10,000.

Here’s a longer answer. Voltage spikes and why they matter. An electrical energy surge on a wire, characterized by a relatively large, short-duration (a few millionths of a second) increase in voltage along that wire, is called a voltage spike. Let’s assume for the sake of this discussion that the “wire” of interest includes the electrical power wiring and electrical devices in your house.

A voltage spike can enter residential wiring in two ways: it can come from the electrical supply lines or cables entering the building, and it can come from within the building. In a typical house, most voltage spikes are caused by devices inside the house that contain a relatively large electrical motors that cycle on and off, such as the motors in an air conditioner or refrigerator.

A voltage spike can cause extensive damage to household electrical devices. How often a voltage spike will occur, and what damage it will do when it does, depends on many factors, including the frequency and severity of thunderstorms, the relative elevation, the kind of electrical appliances, and the wiring configuration, at your site.

The circuit breakers in your house provide no protection against voltage spikes.

What is a surge protector? Almost all electrical/electronic appliances intended for residential use are rated to operate at approximately constant voltage. In a typical US house, that voltage is either about 120 volts, or about 220 volts, depending on appliance. A voltage spike, by definition, can exceed these ratings by hundreds to thousands of volts.

A surge protector is an electrical device that is designed to block, limit, or divert, within specified limits, otherwise damaging electrical energy that arises from a voltage-spike event on the wiring in your house. A whole-house surge protector is a surge protector designed to help protect against the electrical energy effects of voltage spikes that appear on electrical power wiring anywhere your house, regardless of where the spikes originate.

Twenty years ago, few household appliances could be damaged by typical electrical voltage spikes. Today, essentially every household appliance contains electronics (e. g., a “control board”) that can be destroyed by an electrical voltage spike. Replacing just the control board in a major modern household appliance such as a washing machine, electric oven, or dishwasher, for example, can cost $500 per appliance, per incident.

Including the labor of a licensed electrician, a whole-house surge protector costs about $500, installed. Under typical residential conditions, the protector will last at least 10-15 years, the nominal service life of most large residential appliances. If a whole-house surge protector on average saves at least one $1000-appliance every five years, therefore, the protector will more than pay for itself.

Is a whole-house surge protector enough surge protection in a typical residence? No. A high-quality whole-house surge protector is sufficient to protect the electronics in typical large household appliances such as washing machines, dishwashers, refrigerators, electric ovens and ranges, and air conditioners, from anything but a direct lightning strike on your house.

Computers, TVs, radios, and phones connected to external phone lines, in contrast, contain much more sensitive electronics and need special surge protection. You should use a separate surge protector specifically designed to protect sensitive electronics like these. Look closely at the protector’s specification before you buy. The device should be UL listed. The protector’s Joules rating should be more than 2000 joules and have a response time of less than a microsecond (less than 1000 nanoseconds). These devices are available at most hardware and consumer-electronics stores, cost $50 - $100 each, and typically contain several electrical outlets.

A surge protector will not protect your house from a direct lightning strike on your house or on an antenna connected to it. For further information, see or consult a licensed electrician.

Jack K. Horner, W0JKH, Systems Engineer
2130 Owens Lane
Lawrence KS 66046
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Voice: 785-424-7579