Electrical Capacity of Wires

A wire's electrical capacity is measured by how much current it is capable of carrying without overheating and is a function of diameter, or gauge. The larger the gauge, the more current a wire can safely carry.


An electrical wire's carrying capacity is a function of it diameter.

Current does not actually flow through a wire, but rather along it surface.  As such, the larger a wire's gauge, the greater its surface area and the greater its electrical capacity.

Stranded wire, by virtue of its having more combined surface area, has a greater capacity than solid wire of the same diameter. 


As electricity travels along a wire's surface, it faces resistance and loses energy.  The longer the distance, the larger the wire's gauge must be to increase the capacity enough to have a sufficient amount of current reach the end of the wire.


The longer period of time a wire carries a load, the greater the amount of energy it will release as heat.  Wires that carry a steady charge, for devices like lamps and refrigerators, are required to be of a larger gauge than wires used in applications that carry intermittent loads, such as water pumps or garbage disposals.

Photo Credits

  • electric outlet image by Dawn Williams from Fotolia.com