For a standard 200-amp residential dwelling service, the NEC (Article 310.12) mandates a minimum of 2/0 AWG aluminum. For a 100-amp subpanel feeder, use 1 AWG aluminum. For a 60-amp dedicated circuit like an EV charger or subpanel, use 4 AWG aluminum. These baseline picks assume standard 75°C terminations and no extreme ambient temperature derating.
Aluminum is the undisputed king of feeder and service entrance conductors due to its cost-to-weight ratio, but sizing it incorrectly leads to overheated lugs, voltage drop, and failed inspections. Below is the definitive reference for sizing aluminum conductors, built directly from the National Electrical Code.
How to Read This Aluminum Wire Size Chart
This chart is derived directly from NEC Table 310.16 (formerly 310.15(B)(16)) for aluminum conductors. Before you pick a row, you must understand which temperature column applies to your installation. Under NEC 110.14(C), the ampacity of a wire is limited by the lowest temperature rating of any connected termination, conductor, or device.
| AWG / kcmil | 60°C (Amps) | 75°C (Amps) | 90°C (Amps) | Common Application |
|---|---|---|---|---|
| 8 AWG | 30 | 40 | 45 | 30A-40A branch circuits (rare for Al) |
| 6 AWG | 40 | 50 | 55 | 50A range/dryer circuits |
| 4 AWG | 55 | 65 | 75 | 60A subpanels, EV chargers |
| 3 AWG | 65 | 75 | 85 | 75A continuous loads |
| 2 AWG | 75 | 90 | 100 | 100A dwelling service (310.12) |
| 1 AWG | 85 | 100 | 115 | 100A subpanel feeders |
| 1/0 AWG | 100 | 120 | 135 | 125A feeders, 150A dwelling service |
| 2/0 AWG | 115 | 135 | 150 | 200A dwelling service (310.12) |
| 3/0 AWG | 130 | 155 | 170 | 150A subpanel feeders |
| 4/0 AWG | 150 | 180 | 205 | 200A commercial feeders |
| 250 kcmil | 170 | 205 | 230 | 200A subpanel feeders |
| 300 kcmil | 195 | 240 | 265 | 225A feeders |
| 350 kcmil | 225 | 260 | 290 | 250A subpanel feeders |
| 400 kcmil | 245 | 285 | 320 | 300A service entrance |
Quick-Jump Sizing: Common Feeder and Service Scenarios
Stop guessing between dwelling service exceptions and standard feeder rules. Use this decision tree to lock in your exact wire size based on your specific panel and breaker configuration.
| Installation Scenario | Breaker / Load | Concrete Pick (Wire Size) | NEC Reference |
|---|---|---|---|
| 200A Main Residential Service | 200A Main Breaker | 2/0 AWG Aluminum | 310.12(A) Dwelling Exception |
| 200A Subpanel Feeder | 200A Breaker | 250 kcmil Aluminum | 310.16 (75°C Column) |
| 150A Subpanel Feeder | 150A Breaker | 1/0 AWG Aluminum (if load <120A) or 3/0 AWG | 310.16 / 240.4(B) |
| 100A Subpanel Feeder | 100A Breaker | 1 AWG Aluminum | 310.16 (75°C Column) |
| 100A Main Residential Service | 100A Main Breaker | 2 AWG Aluminum | 310.12(A) Dwelling Exception |
| 60A Subpanel / EV Charger | 60A Breaker | 4 AWG Aluminum | 310.16 (75°C Column) |
Applying Derating Factors: When the Base Chart Fails
The ampacities in the chart above assume an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway. If you are running feeders through a hot attic or bundling multiple circuits in a single conduit, you must apply derating factors from NFPA 70 (NEC) Tables 310.15(B)(1) and 310.15(C)(1).
How to calculate derated ampacity:
- Start with the 90°C column value for your wire size. (This is the only time you use the 90°C column).
- Multiply that value by your derating factor (e.g., 80% for 4-6 current-carrying conductors).
- Compare the result to the 75°C column value.
- Your final allowable ampacity is the lower of the two numbers.
Worked Example: You are pulling four current-carrying conductors (two hots, two neutrals for a multi-wire branch circuit or two separate 120/240V feeders sharing a neutral) through a conduit in a 40°C (104°F) attic. You want to use 2 AWG aluminum for a 90A load.
- 2 AWG at 90°C = 100A.
- Conduit bundling (4 conductors) = 80% factor.
- Ambient temp (40°C for 90°C rated XHHW-2) = 0.91 factor.
- Math: 100A × 0.80 × 0.91 = 72.8A.
Because 72.8A is less than your 90A load, 2 AWG aluminum is too small under these conditions. You must upsize to 1 AWG or 1/0 AWG and recalculate.
What This Chart Cannot Tell You
An ampacity chart is only half the battle. If you ignore the physical and electrical realities of aluminum wire, your installation will fail inspection or, worse, cause a fire at the termination lugs.
1. Voltage Drop Over Distance
NEC Table 310.16 does not account for voltage drop. Aluminum has roughly 61% the conductivity of copper, meaning it suffers from voltage drop much faster over long runs. For any feeder run exceeding 100 feet, you should upsize the wire by at least one AWG/kcmil step to keep voltage drop under the recommended 3% limit for feeders (NEC 210.19 Informational Note). If you are running a 200A subpanel to a detached workshop 250 feet away, 250 kcmil will result in severe voltage drop; you will need to step up to 350 kcmil or 400 kcmil aluminum.
2. Conduit Fill Limits
Aluminum wire is thicker than its copper equivalent. When sizing your PVC or EMT conduit, you must consult NEC Chapter 9, Table 1. You cannot exceed 40% conduit fill for three or more conductors. Because aluminum requires a larger AWG for the same ampacity, you will frequently need to bump up your conduit diameter (e.g., moving from 1.5-inch to 2-inch PVC) to accommodate the physical bulk of the aluminum insulation.
3. Termination Torque and Oxidation
Aluminum is highly susceptible to thermal expansion and oxidation. If you strip an aluminum wire and shove it into a lug without preparation, it will loosen over time, leading to high-resistance arcing and melted panelboards. According to manufacturer specifications from companies like Southwire and standard industry practice, you must:
- Wire-brush the exposed aluminum conductor to remove factory oxidation.
- Apply a UL-listed anti-oxidant compound (like Noalox or Penetrox) to the bare strands immediately before insertion.
- Use a calibrated torque screwdriver or torque wrench to tighten the lug to the exact inch-pound specification printed on the breaker or panelboard label (NEC 110.14(D)). Guessing the tightness by hand is a guaranteed way to fail an inspection or start a fire.
