Copper vs Aluminum for Electrical Conductors

## Electrical Properties | Property | Copper (C11000) | Aluminum (1350-H19) | |----------|----------------|--------------------| | Conductivity | 101% IACS | 62% IACS | | Resistivity | 1.72 microohm-cm | 2.83 microohm-cm | | Density | 8.93 g/cm3 | 2.70 g/cm3 | For equal resistance per unit length, an aluminum conductor has 1.6 times the cross-sectional area of copper but weighs only 48% as much. ## Conductor Sizing To carry the same current, aluminum conductors must be upsized by approximately two AWG sizes compared to copper. This means aluminum requires larger conduit and terminations. ## Thermal Expansion and Oxidation Aluminum's CTE (23.1 x 10^-6/degree C) is 35% higher than copper's (17.0 x 10^-6/degree C). Under cyclic loading, aluminum connections can loosen. Aluminum also forms an insulating oxide (Al2O3) that must be broken through at every connection with anti-oxidant paste. Modern aluminum connections use compression connectors, anti-oxidant compound, higher torque values, and AL-CU rated devices. ## Cost Copper costs approximately 8-10 USD/kg; aluminum costs approximately 2-3 USD/kg. For equal conductivity, an aluminum conductor costs roughly 40-50% of the copper alternative. ## When to Choose Each **Choose copper when**: Space is limited, the circuit is small (branch circuits under 100 A), termination reliability is critical, or specifications require copper. **Choose aluminum when**: The circuit is large (feeders above 100 A), weight must be minimized (overhead lines, aerospace), cost savings are significant at scale, and proper aluminum-rated terminations are used.