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: 1.72e-08 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: 2.65e-08 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	Al Amps	Cu Ω/km	Al Ω/km	Cu kg/km	Al kg/km
4/0	195A	150A	0.1608	0.2472	960.685	289.492
3/0	165A	130A	0.2028	0.3117	761.858	229.578
2/0	145A	115A	0.2557	0.393	604.181	182.063
1/0	125A	100A	0.3224	0.4956	479.137	144.383
1	110A	85A	0.4065	0.6249	379.973	114.501
2	95A	75A	0.5126	0.788	301.332	90.803
3	85A	65A	0.6464	0.9936	238.967	72.01
4	70A	55A	0.8151	1.2529	189.51	57.107
6	55A	40A	1.2961	1.9922	119.184	35.915
8	40A	30A	2.0608	3.1677	74.955	22.587
10	30A	25A	3.2768	5.0369	47.14	14.205
12	20A	15A	5.2104	8.009	29.647	8.934
14	15A	—A	8.2848	12.7348	18.645	5.618
16	10A	—A	13.1734	20.2492	11.726	3.533
18	7A	—A	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.