The History of Electrical Wiring in the U.S.

Surge protector with multiple plugs.

This type of overload due to an old home not having enough outlets is dangerous.

Electricity has been a standard part of almost every U.S. home for nearly 100 years. Significant strides have been made over the years to make electricity in homes safer and more reliable. However, as a home inspector, you will likely encounter some old electrical systems that do not conform to modern codes.

While these may still function adequately, you should note on your report any potentially unsafe conditions, including age, wear, and method of installation.

Cloth-Covered Wiring

Today, wires are insulated with plastic or rubber. Many years ago, cloth was used. While this may seem strange today, This Old House confirms that if the wiring is covered and in good condition, it is not considered hazardous. Cloth wiring is often connected with ceramic or porcelain knobs or tubes, which also are safe if they are in good condition. You may, however, note such observations on your report so that the potential homeowner is aware of the situation.

Aluminum Wiring

You may also find some old homes with aluminum wiring instead of copper. While aluminum wiring was considered safe at the time it was installed (1965-1973), the Consumer Product Safety Commission now says it can cause fires more frequently than copper wiring.

Short of rewiring the entire house, which is not practical, the CSPC recommends replacing the ends of each aluminum wire with copper, so that only the copper part is exposed. This too, however, is expensive and labor-intensive, so at the very least, recommend the homeowner retrofit each switch and receptacle with a variety that works better with aluminum, thus better protecting the connection and the home.

Ground Wire

One of the biggest problems with old wiring is the absence of a ground wire. Ground wires became standard in electrical system installations in the 1960s. They are important because they reduce the risk of electric shocks.

Obvious evidence of the lack of ground wiring is the presence of two-hole outlets versus three-hole outlets. The third hole is for the ground connection.

Recommend any two-hole outlets be rewired and replaced with three-hole versions.

Electrical outlet.

Outlets that may come into contact with water should be equipped with GFCIs.


The absence of GFCIs — ground fault circuit interrupters — can also pose risks. These types of outlets with a red reset button are often installed in places like bathrooms and kitchens where, if they were to get wet, the danger of electric shock would greatly increase. The GCFI cuts off the electricity when the circuit gets wet or overloaded.

If GCFIs aren’t installed on outlets or the main box, recommend they be placed at least in bathrooms and kitchens, and possibly in garages or outdoors as well.


Another problem you’ll see with homes wired many years ago is the dearth of available outlets. Homes constructed in the 1940s, 50s, and 60s typically had a couple of outlets per room. Homeowners were expected to have a clock and a lamp plugged in and not much else.

Today homeowners still often plug in clocks and lamps, but also TVs, stereo equipment, electronics chargers, computers, printers, electric blankets, and more. Add to that the appliances you only plug in when you use them — hair dryers, irons, blenders, etc. — and you need even more outlets.

Although this isn’t a code violation, having too few outlets can lead to an unsafe situation if the new homeowner is forced to use lots of power strips or extension cords to operate their appliances and electronics. If a home is lacking in outlets, recommend more be installed.

ICA’s home inspection courses teach you everything you need to know about electrical wiring and inspecting homes. To learn more about our home inspection courses, check out our website today.

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