There was a time when, cost permitting, electricians would choose copper wire over aluminum in virtually every situation. While copper wire, which features better conductivity and more secure termination points, was believed to be far superior to aluminum, limitations in availability made the much more reasonably priced aluminum an almost inevitable competitor.
Weight is the primary reason that utility companies use aluminum wire for power distribution. Aluminum is much lighter than copper, and therefore requires fewer supports for the large wires necessary for distribution. Its weight also makes aluminum wire easier to work with in longer-length runs than heavier copper conductors.
Copper conducts electricity better than aluminum, which means that smaller copper conductors can be used to provide the same power capabilities as would thicker aluminum conductors. This fact often allows for the use of smaller conduit with copper conductors, which is of great benefit in situations where space is an issue.
Prior to improvements and the introduction of aluminum alloys, exposure to the elements caused aluminum to oxidize, creating problems with points of connection. For this reason, copper used to offer a much more secure and longer lasting connection, but improvements to aluminum conductors have greatly reduced the likelihood of problems at termination points.
Cost is the biggest reason that aluminum conductors came to light as an alternative to copper for electrical wiring. Even though the cost of raw materials constantly fluctuates with availability, aluminum wire is consistently less expensive than copper to complete a given job.
The National Electrical Code (NEC) ultimately determines what type of wire can be used for which applications. An electrician's or technician's preference doesn't mean anything if the NEC determines that one type of wire is suitable for a particular application and another is not. Some devices are only approved with terminations for copper wire, and in these instances aluminum conductors are not an option.
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