12 AWG Copper vs Aluminum
At 12 AWG, aluminum wire carries 20% less current than copper but costs roughly 40-60% less per foot and weighs one-third as much. With copper prices rising, 12 AWG aluminum wire is increasingly common for feeders and service entrances where the cost savings are substantial.
Ampacity comparison
All values per NEC 2023 Table 310.16 for THHN insulation with 110.14(C) termination limits applied.
| Property | Copper | Aluminum |
|---|---|---|
| 90°C ampacity | 30A | 25A |
| Usable (after 110.14(C)) | 25A | 20A |
| Breaker | 20A | 15A |
| Conduit (EMT) | 1/2" EMT | 1/2" EMT |
Voltage drop comparison
Voltage drop at 20A load (limited by aluminum capacity) on 240V single-phase.
| Distance | Copper | Aluminum |
|---|---|---|
| 50 ft | 1.6% | 2.7% |
| 75 ft | 2.5% | 4.1% |
| 100 ft | 3.3% | 5.4% |
| 150 ft | 5.0% | 8.1% |
| 200 ft | 6.6% | 10.8% |
When to use each
Use 12 AWG copper when
- You need the full 25A capacity in a single conductor
- Terminal connections are standard (most residential equipment is copper-only rated)
- Space is limited and you need the smallest conduit possible
- Connections will not be accessible for periodic retorquing
Use 12 AWG aluminum when
- 20A is sufficient for your load
- All terminals are AL-rated (marked AL/CU or AL)
- Anti-oxidant compound will be applied at every connection
- Cost savings justify the extra installation care
What to buy
For 12 AWG branch circuits, buy NM-B (Romex) cable for in-wall runs or THHN conductors for conduit. Copper is standard at this gauge since the cost premium over aluminum is small and most devices are copper-rated only. Buy 10-15% more wire than your measured run length to account for routing and termination tails.
Common products for 12 AWG Copper circuits
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Detailed ampacity: 12 AWG copper, 12 AWG aluminum. Wire size lookup: 20A circuit.
Frequently asked questions
Is 12 AWG aluminum safe to use?
Yes, when installed correctly. 12 AWG aluminum carries 20A and is common in feeder circuits. Use AL-rated terminals, apply anti-oxidant compound, and torque connections to manufacturer specs. Modern AA-8000 series aluminum is engineered for building wire.
How much less does 12 AWG aluminum carry than copper?
12 AWG aluminum carries 20A vs 25A for copper, a 5A difference (20% reduction). To match copper ampacity, you typically need to go up 2 gauge sizes in aluminum.
What size aluminum equals 12 AWG copper?
To match 12 AWG copper (25A), check the 20A wire size guide for the exact aluminum equivalent needed.
Can I mix copper and aluminum in the same circuit?
Not directly. Copper and aluminum must not touch at connections due to galvanic corrosion. Use approved bimetallic connectors (like Alumiconn) or AL/CU-rated panel lugs.
NEC 2023 references verified April 2026