If you are sizing an aluminum feeder for a 100A subpanel, use #1 AWG aluminum. If you are pulling a 200A residential service entrance, use 2/0 AWG aluminum. For a 60A circuit (like an EV charger or small workshop panel), use #4 AWG aluminum.

Aluminum wire (typically XHHW-2, THHN/THWN-2, or SER cable) is the standard for modern feeders and service entrances due to its cost-to-weight ratio. However, sizing it incorrectly leads to melted lugs, nuisance tripping, or failed inspections. The chart and decision paths below are based on the NFPA 70 (National Electrical Code) Article 310.16, updated for current installation practices.

The Master Aluminum Wire Gauge Chart (NEC 310.16)

How to read this table: This chart displays the allowable ampacities for insulated aluminum conductors rated up to 2000V. You will see two primary columns: 75°C and 90°C.

The Golden Rule of Terminations (NEC 110.14(C)): Unless your breaker, lug, or terminal block is explicitly marked for 90°C (which is exceptionally rare in residential and light commercial gear), you must size your breaker and wire based on the 75°C column. The 90°C column is strictly reserved for calculating derating adjustments before you terminate the wire.
Table 310.16 Allowable Ampacities for Aluminum Conductors (Not more than three current-carrying conductors in raceway, 30°C ambient)
Wire Size (AWG/kcmil) 75°C Column (Termination Sizing) 90°C Column (Derating Base) Common Application
#8 AWG40A45ASmall branch circuits (rare for Al)
#6 AWG50A55A50A EV chargers, AC disconnects
#4 AWG65A75A60A subpanels, large EV chargers
#3 AWG75A85A75A feeders
#2 AWG90A100A100A feeders (with 90°C lugs)
#1 AWG100A115AStandard 100A subpanels
1/0 AWG120A135A125A feeders, mobile home services
2/0 AWG135A150A150A panels, 200A dwelling service*
3/0 AWG155A175A175A feeders
4/0 AWG180A205A200A non-dwelling feeders/services
250 kcmil205A230A225A services, large commercial feeders

*See NEC 310.12 for the dwelling service exception allowing 2/0 AL on 200A residential mains.

Quick-Jump: Most Queried Aluminum Wire Sizes

Bookmark this section for the most common jobsite scenarios. These assume standard 75°C terminations and an ambient temperature of 30°C (86°F) or less.

  • 200A Residential Service Entrance: Use 2/0 AWG Aluminum (SER or USE-2). Why? NEC 310.12(A) specifically allows 2/0 AL for 200A single-phase dwelling services, bypassing the standard 310.16 requirement of 4/0 AWG.
  • 100A Subpanel Feeder: Use #1 AWG Aluminum (THHN in conduit or SER cable). #1 AL is rated exactly 100A in the 75°C column.
  • 60A Circuit (EV Charger / Workshop): Use #4 AWG Aluminum. Rated for 65A at 75°C, it safely covers a 60A continuous or non-continuous load.
  • 50A Range or Hot Tub Disconnect: Use #6 AWG Aluminum. Rated for 50A at 75°C.

Decision Tree: Sizing Your Aluminum Feeder or Branch Circuit

Use this decision path to lock in your exact wire size. Do not guess; follow the load calculation to the terminal pick.

If Your Calculated Load / Breaker Size Is... And Your Installation Is... Then Your Exact Aluminum Wire Pick Is...
200 Amps Single-family dwelling service entrance 2/0 AWG AL (per NEC 310.12)
200 Amps Non-dwelling (commercial, detached garage subpanel) 4/0 AWG AL (per NEC 310.16 75°C col)
125 Amps Standard subpanel feeder 1/0 AWG AL (120A rating is insufficient for 125A breaker; must use 1/0 for 120A+ or upsize to 2/0 if exactly 125A breaker. *Correction: Use 2/0 AWG AL for a 125A breaker).
100 Amps Standard subpanel feeder (30°C ambient, ≤3 conductors) #1 AWG AL
60 Amps Continuous load (e.g., EV charger running ≥3 hours) #3 AWG AL (Wire must be rated 125% of continuous load = 75A)
60 Amps Non-continuous load (e.g., standard subpanel, welder) #4 AWG AL

Derating and Ambient Temperature Adjustments

The base ampacities in the chart above assume two things: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors (CCCs) in a single raceway. When real-world conditions violate these assumptions, you must apply derating factors using the 90°C column as your starting math baseline.

Real-World Derating Example: The 100A Conduit Run

Suppose you are pulling a 100A subpanel feeder through a conduit that already contains another circuit, resulting in four current-carrying conductors in the pipe.

  1. Identify the derating factor: NEC Table 310.15(C)(1) dictates an 80% adjustment factor for 4-6 CCCs.
  2. Check your base wire: #1 AWG AL in the 75°C column is 100A. But we must use the 90°C column for derating math. #1 AWG AL at 90°C is 115A.
  3. Apply the math: 115A × 0.80 = 92A.
  4. The Result: 92A is less than your 100A breaker. The #1 AWG wire is now undersized and will fail inspection.
  5. The Fix: Upsize to 1/0 AWG AL. 1/0 at 90°C is 135A. 135A × 0.80 = 108A. Since 108A is greater than 100A, 1/0 AWG AL is your legal, safe pick.
Ambient Temperature Warning: If your conduit runs across a rooftop or through a hot attic where ambient temperatures exceed 30°C, you must apply the temperature correction factors from NEC Table 310.15(B)(1). For example, in a 45°C (113°F) attic, you must multiply your 90°C base ampacity by 0.87.

What This Chart Cannot Tell You (And How to Fix It)

An ampacity chart is a thermal limit chart; it tells you the point at which the wire's insulation will melt. It does not account for voltage drop, physical pulling limits, or local amendments. Here is how to handle the blind spots.

1. Voltage Drop Over Distance

NEC 310.16 does not penalize you for distance, but physics does. If you are running a 100A aluminum feeder to a detached garage 150 feet away, #1 AWG AL will experience roughly a 4.5% voltage drop at full load. This exceeds the NEC informational note recommendation of 3% for feeders. The Fix: For any aluminum feeder run exceeding 100 feet, upsize by one AWG step (e.g., use 1/0 AWG instead of #1 AWG for a 100A run) to keep voltage drop under 3%.

2. Physical Pulling Tension and Bending Radius

Aluminum wire, particularly larger sizes like 4/0 AWG SER cable, is stiff and prone to work-hardening and cracking if bent repeatedly. The NEC mandates specific bending radii (typically 5 to 7 times the cable diameter depending on the jacket). The Fix: Use wide-sweep 90-degree fittings or pull boxes instead of sharp conduit bends. When terminating large aluminum wire into lugs, always use a calibrated torque screwdriver or torque wrench to the manufacturer's exact inch-pound specification to prevent cold flow and subsequent arcing.

3. Anti-Oxidant Compound Requirements

While modern AA-8000 series aluminum alloy wire is vastly superior to the problematic 1970s branch wiring, aluminum still oxidizes. The Fix: Always apply a UL-listed anti-oxidant compound (such as Noalox or Ideal No-Ox-Id) to the stripped aluminum conductor before inserting it into a mechanical lug. Note: Some modern torque-rated lugs come pre-filled with compound; check the manufacturer spec sheet before double-dosing, which can cause hydraulic lockout and improper seating.

4. Local AHJ Restrictions

Some local Authorities Having Jurisdiction (AHJs) prohibit the use of aluminum wire for branch circuits under 50A, or ban it entirely in certain residential applications due to historical biases. The Fix: Always verify with your local building department before purchasing aluminum for 15A, 20A, or 30A branch circuits. For feeders (50A and above), aluminum is universally accepted and is the industry standard.