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Copper vs Aluminum Wire

A side-by-side comparison of the two most common conductor materials. Copper has better conductivity; aluminum is lighter and cheaper. The right choice depends on your application.

Copper

Resistivity: 1.72 × 10⁻⁸ Ω·m

Density: 8,960 kg/m³

Temp coefficient: 0.00393/°C

Conductivity: 100% IACS (reference standard)

Advantages

  • Best practical conductivity (after silver)
  • Higher ampacity for the same wire size
  • More ductile — easier to work with
  • Better corrosion resistance
  • Standard for residential wiring (NEC)

Aluminum

Resistivity: 2.65 × 10⁻⁸ Ω·m

Density: 2,700 kg/m³

Temp coefficient: 0.00429/°C

Conductivity: ~61% IACS

Advantages

  • ~70% lighter than copper
  • Significantly cheaper per foot
  • Preferred for utility and feeder cables
  • Adequate for large-gauge applications
  • Standard for overhead power lines

Side-by-Side: Ampacity, Resistance & Weight

AWG Cu Amps (75°C) Al Amps (75°C) Cu Ω/km Al Ω/km Cu kg/km Al kg/km
4/0 230A 180A 0.1608 0.2472 960.685 289.492
3/0 200A 155A 0.2028 0.3117 761.858 229.578
2/0 175A 135A 0.2557 0.393 604.181 182.063
1/0 150A 120A 0.3224 0.4956 479.137 144.383
1 130A 100A 0.4065 0.6249 379.973 114.501
2 115A 90A 0.5126 0.788 301.332 90.803
3 100A 75A 0.6464 0.9936 238.967 72.01
4 85A 65A 0.8151 1.2529 189.51 57.107
6 65A 50A 1.2961 1.9922 119.184 35.915
8 50A 40A 2.0608 3.1677 74.955 22.587
10 35A 30A 3.2768 5.0369 47.14 14.205
12 25A 20A 5.2104 8.009 29.647 8.934
14 20A — 8.2848 12.7348 18.645 5.618
16 13A — 13.1734 20.2492 11.726 3.533
18 10A — 20.9466 32.1974 7.374 2.222

When to Use Which?

Choose Copper When:

  • Residential branch circuits (NEC standard)
  • Space-constrained installations
  • Connections to outlets and switches
  • Marine or corrosive environments
  • High-flex applications

Choose Aluminum When:

  • Service entrance cables (SE cable)
  • Large feeder runs (cost savings)
  • Overhead power lines
  • Utility-scale installations
  • Weight is a concern (long spans)

Important: When using aluminum wire, you must use AL-rated connectors and devices. Mixing aluminum wire with copper-only connectors is a fire hazard due to galvanic corrosion and different thermal expansion rates. Always follow NEC requirements for aluminum connections.

Related

Wire types and insulation ratings → Circuit breaker size chart → NEC Table 310.16 — conductor ampacity →