Metals used for Conductors

Copper

The most commonly used conductor in electrical wiring is copper. NEC 110.5 clearly states “Conductors normally used to carry current shall be of copper unless otherwise provided in the NEC. Where the conductor material is not specified, the material and the sizes given in the NEC shall apply to copper conductors. Where other materials are used, the size shall be changed accordingly.” In other words, copper is the default conductor material unless explicitly stated otherwise.

Copper is the most common form of electrical wiring for several reasons. First off, copper is very malleable and ductile. This means that it can easily be shaped and rolled during the production process which is very useful when creating the stranded copper that comprises wiring.

The second reason that copper is commonly used in electrical wiring is it is highly conductive. Copper has the second highest conductivity (behind only silver) of an element due to the fact that virtually all valence electrons take part in conduction. Since electricity is essentially the flow of electrons from a negative charge to a positive charge, this makes copper very useful as a conductor.

As noted above, copper is the second most conductive element. Silver is the most conductive material but due to its price, copper is is best suited for electrical wiring. In fact, copper is much less expensive than silver. As of this writing, copper is sold for approximately $1.50 per pound whereas silver costs $21.00 per ounce or $336.00 per pound. The price of silver makes it unfeasible to use it in residential and commercial construction which leaves copper as the best alternative.

Aluminum

Aluminum is the second most commonly used conductor in electrical wiring. In some ways it has advantages over copper. It is lighter and more flexible than copper. This obviously has its advantages during the production phase and also during the installation of the electrical devices.

Aluminum is also cheaper than copper. As of this writing it is approximately $.67 per pound versus $1.50 per pound for copper.

One of the cons to using aluminum is that aluminum requires a heavier wire gauge than copper. For example: to power a 60amp device, #6awg copper is required. But if aluminum is used, the wire size jumps to #4awg which is a bigger wire. This makes the copper aluminum price very close.

Even worse, aluminum has been stung by a stigma created in the 1960’s which is why copper is more commonly used. At that time, the price of copper spiked so it became more common for aluminum to be massed produced and installed in homes for all wiring --- branch circuits and the main feeder. Despite the fact that producers and electricians knew that a heavier gauge wire would be required, nobody realized the problem with connecting aluminum wire to the copper terminals of the power receptacles. The dissimilar metals would overheat and caused house fires which in turn branded aluminum as dangerous.

During the 1970’s, provisions were made industry-wide to correct the issue with the terminals. Today, Aluminum is primarily used for main feeders only. And, it is still more affordable than copper.

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