Over the life of a building wire system, copper can also be the most economical conductor.

Copper used in building wire has a conductivity rating of 100% IACS[10][25] or better. Copper building wire requires less insulation and can be installed in smaller conduits than when lower-conductivity conductors are used. Also, comparatively, more copper wire can fit in a given conduit than conductors with lower conductivities. This greater “wire fill” is a special advantage when a system is rewired or expanded