Copper vs Aluminum Wire: Weight vs Performance
The eternal trade-off between conductivity, weight, and cost in electrical design.
Quick Answer
Choose Copper for most applications. It has the best conductivity per volume, resists corrosion, and is the standard for everything from electronics to building wiring.
Choose Aluminum when weight or cost is the primary driver (e.g., aircraft power feeders, long-distance utility lines), provided you use compatible terminals.
Head-to-Head Comparison
| Factor | Copper | Aluminum |
|---|---|---|
| Conductivity | 100% IACS | 61% IACS |
| Weight (Density) | 8.96 g/cm3 | 2.70 g/cm3 (70% lighter) |
| Size for Same Current | Standard | ~1.5x Larger Area (+2 AWG sizes) |
| Cost | Higher | 50-70% Less |
| Corrosion Resistance | Excellent | Needs protection (oxidizes) |
| Best For | General purpose, electronics | Utility lines, aircraft |
Physical Properties
| Property | Copper | Aluminum |
|---|---|---|
| Resistivity (Ohm m) | 1.72 x 10^-8 | 2.82 x 10^-8 |
| Density (g/cm3) | 8.96 | 2.70 |
| Melting Point | 1085 C | 660 C |
| Thermal Expansion | 16.5 um/(m K) | 23.1 um/(m K) |
Common Mistakes
Mixing Copper and Aluminum
Directly connecting Cu and Al wires creates a battery (galvanic cell) that rapidly corrodes the aluminum, leading to high resistance and fire. Always use rated bi-metallic connectors.
Ignoring Bend Radius
Aluminum is more brittle than copper. Because aluminum wires are larger for the same current, they require a significantly larger bend radius to prevent cracking.
Using Copper Lugs on Aluminum Wire
Standard copper lugs are not compatible with aluminum wire due to thermal expansion differences. Aluminum expands more when hot, and will deform inside a rigid copper lug, becoming loose when it cools down.
Frequently Asked Questions
Calculate Your Cable Weight
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