Copper vs Aluminium Conductors

Conductivity and cross-section

Copper has roughly 61% higher conductivity by volume than aluminium. To carry the same current, an aluminium conductor typically needs to be one to two sizes larger — for example a 4/0 AWG aluminium feeder to replace a 2/0 AWG copper one.

That larger cross-section drives up the outside diameter of the finished cable, which in turn affects conduit fill, tray loading, bend radius and gland selection. On a congested riser or a retrofit, the space penalty alone can rule aluminium out.

Terminations and long-term reliability

Aluminium forms a tenacious oxide layer and creeps under sustained mechanical load, so terminations require anti-oxidant compound, correctly rated AL/CU lugs and a documented re-torque regime. Copper terminations are far more forgiving.

Where a joint is inaccessible, safety-critical, or subject to heavy thermal cycling, copper's stability is usually worth the premium. Most of the connection failures we are asked to investigate trace back to aluminium terminations that were never re-torqued.

Total installed cost, not metal price

Aluminium is cheaper per kilogram and lighter per metre, which reduces both material spend and pulling labour on long runs. On a large outdoor feeder with generous containment, that can be decisive.

• Long, straight, accessible feeders with space to spare: aluminium often wins
• Branch circuits, panel interiors, control and instrumentation: copper
• Vibration, thermal cycling or corrosive atmospheres: copper
• Weight-limited structures and very long runs: model both options