How much larger must aluminum wire be compared to copper wire to achieve the same conductivity?

Aluminum wire must be significantly larger than copper wire to achieve the same conductivity due to the inherent differences in their electrical properties. Specifically, aluminum has a lower conductivity than copper—approximately 61% that of copper. Therefore, in order to compensate for this lower conductivity, the diameter of aluminum wire needs to be increased.

The factor by which aluminum must be larger than copper to achieve the same conductivity is approximately 1.66 times. This means that if you have a certain gauge of copper wire, you would need an aluminum wire that is roughly 1.66 times the cross-sectional area of the copper to ensure they can carry the same amount of current without overheating or causing losses.

Understanding this ratio is essential for linemen when selecting wire types for electrical installations, as it impacts not only the performance of the electrical system but also the physical size and weight of the materials being used.