Copper vs Aluminum Wire: Cost, Ampacity & NEC Rules
Copper vs Aluminum Comparison
| Property | Copper | Aluminum |
|---|---|---|
| Ampacity (6 AWG, 60°C) | 55A | 40A |
| Ampacity (1/0 AWG, 75°C) | 150A | 120A |
| Conductivity | 100% (baseline) | 61% |
| Cost per ft (1/0 AWG) | $3.00–4.00 | $1.50–2.50 |
| Weight per ft (1/0 AWG) | 0.36 lbs | 0.17 lbs |
| Thermal expansion | Low | Higher (requires AL-rated connectors) |
| NEC Branch Circuit Use | All sizes approved | Approved with CO/ALR devices |
Frequently Asked Questions
Is copper wire better than aluminum?
Copper has higher ampacity per gauge, better conductivity, and doesn't expand/contract as much. Aluminum is cheaper and lighter but requires larger gauge for the same current. For branch circuits (15-50A), copper is standard. For service entrance (100A+), aluminum is common and cost-effective.
Why is aluminum wire considered a fire hazard?
Older aluminum wiring (1960s-70s, AA-1350 alloy) had expansion/contraction issues that loosened connections, causing fires. Modern AA-8000 series aluminum wire with CO/ALR connectors is safe and NEC-approved. The old alloy was banned in 1978.
When should I use aluminum wire?
Use aluminum for: service entrance conductors (100A+), sub-panel feeders, and large commercial feeders. Use copper for: branch circuits (15-50A), receptacle connections, and any terminations not rated AL/CU.
Disclaimer: For preliminary design only. Verify against local codes and professional engineering requirements.