Pick the conductor by its job. Use copper for branch circuits and any small or tight termination — it's more forgiving and comes in small sizes. Use modern aluminum (AA-8000 alloy) for large feeders and service-entrance conductors, where its ~half weight and roughly one-third to one-half the cost win big; you just upsize about two AWG sizesfor the same ampacity. Both are safe and code-approved when installed to spec. The “aluminum is dangerous” reputation belongs to 1965–1973 solid AA-1350 branch wiring, not the aluminum feeders used today.
Choosing a conductor is two decisions — the material and the size. This page covers the material; once you've picked, size it with the free Wire Size Calculator, and for a service or subpanel, the subpanel and load calculators.
⚖️ Aluminum vs. Copper at a Glance
Head to Head
| Factor | Copper | Aluminum (AA-8000) |
|---|---|---|
| Conductivity | 100% IACS (reference) | ~61% IACS — upsize ~2 AWG |
| Weight | Heavier | ~half, for the same resistance |
| Cost per foot | Higher (volatile) | ~⅓ to ½ of copper |
| Small sizes | Down to 16–18 AWG | Uncommon below 6 AWG |
| Terminations | Forgiving | Need AL-rated devices/lugs + torque |
| Best for | Branch circuits, tight spots | Services & large feeders |
Both are code-approved. The choice is about circuit role, not safety.
📏 Sizing: aluminum runs about two sizes up
Aluminum carries about 61% of copper's current for the same gauge, so for equal ampacity you step up roughly two AWG sizes. From NEC Table 310.16 (75°C), the common service/feeder pairings:
- 100 A: 3 AWG copper ≈ 1 AWG aluminum
- 150 A: 1/0 copper ≈ 3/0 aluminum
- 200 A: 3/0 copper ≈ 250 kcmil aluminum
- 400 A: 600 kcmil copper ≈ 800 kcmil aluminum
Dwelling services use smaller numbers. NEC Table 310.12 (the “83% rule”) lets a 120/240 V dwelling service carry conductors rated 83% of the service — so a 200 A service uses 2/0 copper or 4/0 aluminum, and a 100 A service uses 4 AWG copper or 2 AWG aluminum. That's because a house rarely draws its full rating.
The upsize means bigger conduit and lugs, but the conductor is far lighter and easier to pull — a real advantage on long or parallel service runs. Let the wire size calculator handle the exact gauge in either metal.
🔩 Terminations: where aluminum needs care
Aluminum isn't hard to terminate — it's just unforgiving of the wrong parts or a sloppy connection. Three rules cover it:
- Aluminum-rated devices and lugs. Receptacles and switches must be marked CO/ALR; breakers and lugs must be marked AL-CU (or AL7CU/AL9CU). A device not so marked is for copper only (NEC 110.14, UL 486A-B / UL 498).
- Correct torque, with a calibrated tool. Aluminum “creeps” (cold-flows) under pressure, so an under-torqued screw works loose and an over-torqued one shears. NEC 110.14(D) requires torquing to the manufacturer's spec with an approved means.
- Oxide inhibitor when the maker calls for it. Aluminum grows an insulating oxide layer in air; antioxidant compound (Noalox, Penetrox) breaks and excludes it. It's required only when the connector's instructions say so — not universally.
Get those right and an aluminum feeder is every bit as reliable as copper. Get them wrong and you get the loose, hot connection that gives aluminum its bad name — which is exactly what happened in the 1960s.
🕰️ The “aluminum is dangerous” myth
The fear is real but misplaced. Between 1965 and 1973, with copper prices high, builders ran solid AA-1350 (utility-grade) aluminum for 15- and 20-amp branch circuits in an estimated two million homes. That old alloy crept and oxidized at receptacle and switch screws, loosening connections until they overheated. The CPSC found pre-1972 aluminum-wired homes were far more likely to have outlet connections reach fire-hazard temperatures than copper-wired homes.
Modern aluminum is a different alloy. Since the mid-1970s, aluminum building wire is AA-8000 series, engineered to creep and behave like copper at terminations (ASTM B800). It's UL-listed, NEC-recognized, and used mainly for feeders and services — not small branch circuits. The old-technology problem does not apply to it.
If you own a pre-1974 home, find out whether it has solid AA-1350 branch wiring — it affects safety, insurability, and disclosure at sale. The only permanent fixes the CPSC recognizes are a full copper rewire, COPALUM crimps, or AlumiConnconnectors. Ordinary wire-nut “pigtailing” is not a permanent repair and can make things worse.
🏗️ Where each is standard today
Copper
- 15/20 A branch circuits and lighting
- Small conductors (below 6 AWG)
- Tight, crowded, or critical terminations
- Corrosive, coastal, or damp locations
- Matching or extending existing copper
Aluminum (AA-8000)
- Service-entrance conductors & most 200 A services
- Large feeders — subpanels, detached buildings, EV
- Long or parallel runs (weight & cost)
- Mobile-home feeders
- Utility service drops
💰 Cost: aluminum wins big at large sizes
For the same ampacity, aluminum runs roughly one-third to one-half the cost of copper per foot, and the gap widens as conductors get larger. On a 200 A service, 4/0 aluminum is a fraction of the price of the equivalent copper — a difference that can run from a few hundred dollars on a short lateral to well over a thousand on a long run. That's why utilities and most service upgrades use aluminum, and why copper mainly earns its premium on branch circuits where the material cost is small.
Copper is volatile — re-price at purchase. Copper hit record commodity highs in 2026 and analysts disagree sharply on where it goes next. If copper retreats hard, the per-foot gap narrows and copper feeders get more attractive; when it spikes, aluminum's advantage grows. Always quote both metals the week you buy.
Prices last reviewed August 2026. Copper is a volatile commodity — it hit record highs in 2026 — so finished-wire prices move fast. Treat these as wide relative ranges, not quotes, and re-price both metals at the moment of purchase.
✅ The bottom line
Both metals are safe and code-compliant when installed correctly — this is a role decision, not a safety one. Default to copper for branch circuits (the savings from aluminum are negligible below ~60 A and not worth the termination fuss). Default to modern aluminum for service entrances and large feeders, where its cost and weight advantages are large — as long as you use AL-rated lugs, a calibrated torque tool, and any oxide inhibitor the maker specifies.
NEC table values here reflect the 2023 edition (75°C column); the core copper/aluminum ampacities are unchanged from 2020 through 2026, but adopted editions and local amendments vary — confirm with your AHJ, and have a licensed electrician verify service and feeder work. Size your run in either metal with the wire size calculator.
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