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McGarry and Madsen's home inspection blog for buyers of
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Can old electrical wiring increase my electric bill?
Sunday, December 30, 2018
Copper wire, with the insulation intact, can last 100 years and longer if left undisturbed and in a dry location. The age of the wiring itself does not usually cause problems, but the things that have happened to it since the home was built can make the wiring inefficient and, as a result, raise your electric bill in several ways:
- A house with 60 or 100-amp service from the 1950s or earlier were not designed for the higher electricity usage of today. Kitchen circuits, in particular, were not intended to be connected to multiple countertop appliances. Large window air conditioners plugged into a regular wall receptacle are another example. The wiring is undersized for the amperage of the appliances, which raises the resistance to the flow of electricity and costs more.
- Squirrels or rodents in the attic gnaw on wires, which creates hot spots and sometimes arcing, both of which will raise your bill and are a safety problem.Also, people climbing around in the attic and moving boxes around can damage wiring over time, especially near attic hatch openings, like below.
- Many homes built before 1950 have wiring with cloth insulation that becomes brittle and flakes off with age. The knob-and-tube wiring (see What is "knob and tube" wiring?) at the top of this page is one example, and another one is shown below inside a panel. Deterioration of the insulation creates potential for arcing and electrical leakage.
- Faulty wiring, switches, and receptacles added over the years by a handyman or homeowner can have excessive resistance at the connections and overly long circuit runs, both of which increase electric usage.
- Moisture intrusion from a long-term roof or wall leak, or a flooding event, corrodes electric connections and fixtures—again, reducing efficiency and safety.
A licensed electrician can advise you on any uprgrades of your wiring that might be necessary to improve the system’s efficency and safety. And, although all of these problems with older wiring may increase your electric bill, other defects may be the culprits. See our blog post What could cause an extremely high electric bill? for more.
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