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Your home electrical system: how long can it last?

Jim Mallery | Improvement Center Columnist | April 25, 2013

You probably don't think about the lifespan of the various components of your home's electrical system until the power goes out. If the rest of the neighborhood hasn't blacked out, it might cross your mind something in your house has failed.

Nick Gromicko of the International Association of Certified Home Inspectors (NACHI) has expanded on a report by the National Association of Home Builders (NAHB) and compiled a list of the life expectancies for key components of residential electrical systems. Following is a rundown on how long you might expect certain of these elements to last, based on data from both the NACHI and NAHB reports -- as well as what it might currently cost you to replace some of them.

Wiring

The most obvious component of your electrical system is the wiring. Both NACHI and NAHB charts agree that copper wiring can last 100 years or more. But the real life expectancy of your wiring is not in the copper; it's dependent on the wiring's insulation, and that lifetime can vary widely.

For instance, the ancient knob-and-tube form of wiring might be only 70 years old, but experts recommend it should be replaced if the insulation has become brittle. The industry began phasing it out in the 1930s.

Likewise, the wiring that succeeded knob-and-tube, two wires bundled in rubber and fabric, has also turned brittle, and you might see problems with it in homes built before 1960. That kind of insulation was replaced by an early version of thermoplastic insulation -- called NM for non-metallic. The modern formula for thermoplastic NM-B type wiring dates from 1984, when the insulation's heat resistance was increased; the best guess is that it will provide over 100 years of service, but it's a little early to tell.

Installation

Complicating estimates of lifespan is the assumption that the product was installed properly -- which isn't always the case.

In the instance of wiring, temperature has a considerable effect on the insulation, and it is possible some wiring has been installed in an unusually warm area. Also, a number of wires packaged in the same run, especially if the wires are carrying heavy electrical loads, can increase temperatures and reduce the insulation's lifetime.

Pinched wires also can be a danger of poor installation. If a wire staple was hammered too tightly, it may have pinched the insulation. It may not cause an immediate problem, but over several years with tiny vibrations in the house, the insulation can fail.

Service panels

The electrical service panel is the box that holds your circuit breakers. The panel takes the power line from the street and distributes the current to the circuits in the house. It has its own "main" breaker that cuts power to the entire house with the flip of the switch.

According to the NACHI chart, service panels have an average life expectancy of 60 years, though the lifetime of a panel can vary greatly. Corrosion from a humid location or excessive dust can shorten its life. While warranties are not necessarily good indicators of how long something will last, they can give you an inkling.

Two common brands of panel -- Square D and Cutler-Hammer -- make two grades of service panels, and in each case, the less expensive, residential version carries a 10-year warranty while the commercial brand carries a lifetime warranty. Square D's pricing for a 200-amp panel is $163/$261, and Cutler-Hammer's is $120/$171.

Breakers

The circuit breakers are more likely to fail than the panel. A breaker that is tripped often is more likely to fail, though most breakers nowadays are rated to work as switches. The NACHI chart says that ground-fault circuit interrupters and arc-fault interrupters have a life of about 30 years, though a 2003 report prepared for the United States Consumer Product Safety Commission says arc- and ground-fault breakers, as well as regular circuit breakers, have a lifetime of 30 to 40 years.

Common circuit breakers cost from under $5 to $10 (220-volt are typically more); ground- and arc-fault breakers can be $30 to $50. Cost is less of an indicator of longevity with breakers; the common brands are cheaper and the harder-to-find are more expensive. If you are looking for a breaker for a panel that is no longer in production, such as Zinsco or Federal Pacific, you could pay from $40 to over $100.

Receptacle GFCIs

Ground-fault interrupters also are made as receptacles, looking very much like a plug receptacle in the wall. These cost between $10 and $16, much less than the circuit-breaker style. They have a shorter lifespan, but their low cost makes them a popular option to the breaker.

Switches and receptacles

The NACHI chart says that lighting controls have an average life expectancy of 30 years, but of course, the lifetime of a switch is inversely proportionate to the frequency of its use. A little-used switch can last for ages; if used often, it will die much sooner. The same is true of a receptacle. If it constantly has a plug pushed in and pulled out, it is likely to fail much sooner. Cold and damp locations can also shorten their lifespan.

Cheaper switches generally tend to wear out sooner. You can buy your switches and receptacles for well under a dollar each from the bulk bins at your big box store, but don't expect them to sustain constant use. Better to pay three times the bulk price or more, and get a long-lasting, dependable switch.

Bulbs

The light-bulb technology is changing almost as fast as computer technology. The NACHI chart says the typical, standard incandescent bulb, now becoming obsolete, lives 1,000 to 2,000 hours. By comparison, the compact fluorescent bulb (CFL), according to the chart, should give you 8,000 to 10,000 hours of use; and the new kid on the block, the LED (light-emitting diode) bulb, should work for 30,000 to 50,000 hours.

A significant advantage of the CFLs and LEDs is their reduced energy consumption -- CFLs use a fraction of the energy of incandescent bulbs, and LEDs use maybe half the energy of CFLs.

With the longer lifespan of the current bulbs comes increased cost, but just as the fluorescent bulbs plummeted in price as they became more common, the price of LED bulbs also is falling. In the early days of LEDs, you might pay $60 for a bulb. Now, Costco is selling 60-watt replacement LED bulbs for $10 (25,000 hours projected lifespan, or 22.8 years); Costco has a 75-watt replacement Par38 flood bulb rated at 30,000 hours for $26. Home Depot and Lowe's charge around twice as much for bulbs comparable to Costco's, but they also carry a much wider selection of LEDs.

While the NACHI chart gives LEDs credit for 30,000 to 50,000 hours, many of the current LED bulbs are labeled at from 25,000 to 40,000 hours.

Accessories

Both the NACHI and NAHB charts project an average life expectancy of 10 years for the catch-all category of accessories. Here are some examples:

  • Timer: Your fan or heater in the bathroom may be on a timer. If it is a spring-loaded timer and you use it often, you may have to replace it after a few years. But if it is an electrical timer, it can have a longer lifespan. A spring timer will cost a few dollars; an electrical one, in the teens.
  • Sensor switch: A photosensitive switch, such as one that turns on an outdoor light at dusk, might have to be replaced after several years. They loose their sensitivity over time.
  • Alarms: A smoke alarm has to be replaced periodically; the U.S. Fire Administration says they have a lifespan of eight to 10 years. A carbon monoxide alarm has a lifespan of five to seven years; many carbon monoxide monitors are designed to alert you when they need to be replaced.

There is probably very little that's more basic to our home life than electricity: we depend on so much that runs on it. Have a qualified electrical contractor evaluate, repair or replace any worn components of your electrical system, and the only electrical failures you should ever have are the ones that are completely out of your control.

About the Author

Jim Mallery, a semi-retired journalist and onetime registered contractor, has extensive experience remodeling, repairing and rebuilding homes.