When sizing feeders or service entrance conductors, the aluminum wire amp chart is your single source of truth. Governed by NEC Table 310.16, this chart dictates the maximum continuous current an aluminum conductor can carry before its insulation degrades. For a standard 200-amp residential service, you need 4/0 AWG aluminum (per NEC 310.12). For a 100-amp subpanel feeder, you need 1 AWG aluminum. But pulling the right AWG is only half the battle; knowing which temperature column to read and how to apply derating factors is where most DIY installs fail inspection.
How to Read the Aluminum Wire Amp Chart (NEC 310.16)
The aluminum wire amp chart is divided into three primary temperature columns: 60°C (140°F), 75°C (167°F), and 90°C (194°F). These columns represent the maximum temperature rating of the wire's insulation (e.g., TW, THHW, THHN/XHHW-2). However, you cannot simply default to the highest number. The column you must use is dictated by the terminations at both ends of the circuit, governed by NEC 110.14(C).
- 100 Amps or Less: You must use the 60°C column, unless the equipment is specifically marked for 75°C.
- Over 100 Amps: You must use the 75°C column. Most modern main breakers and subpanel lugs are rated for 75°C.
- The 90°C Column: This is strictly used for derating calculations (ambient temperature or bundling adjustments). Your final derated ampacity cannot exceed the 60°C or 75°C termination limits.
Assumptions for the chart below: Pure aluminum or copper-clad aluminum (CCA), single conductors in free air or standard conduit, 30°C (86°F) ambient temperature, and no more than three current-carrying conductors in a raceway. Always verify local AHJ requirements, as some jurisdictions restrict aluminum branch circuits entirely.
Complete Aluminum Wire Ampacity Chart
The following data is sourced directly from NFPA 70 (NEC) Table 310.16 and cross-referenced with Cerro Wire ampacity tables. Use this as your master reference for XHHW-2, THHN, and SER cable installations.
| AWG / kcmil | 60°C (140°F) Ampacity | 75°C (167°F) Ampacity | 90°C (194°F) Ampacity | Common Application |
|---|---|---|---|---|
| 8 AWG | 30A | 40A | 45A | Small 240V appliance feeds |
| 6 AWG | 40A | 50A | 60A | 50A EV charger / Range feed |
| 4 AWG | 55A | 65A | 75A | 60A subpanel feeder |
| 3 AWG | 65A | 75A | 85A | 75A continuous loads |
| 2 AWG | 75A | 90A | 100A | 90A feeder / Grounding electrode |
| 1 AWG | 85A | 100A | 115A | 100A subpanel feeder |
| 1/0 AWG | 100A | 120A | 135A | 100A service / 120A feeder |
| 2/0 AWG | 115A | 135A | 150A | 125A continuous / 150A panel |
| 3/0 AWG | 130A | 155A | 170A | 150A service entrance |
| 4/0 AWG | 150A | 180A | 205A | 200A residential service (310.12) |
| 250 kcmil | 170A | 205A | 230A | 200A commercial / High-load feed |
- 100-Amp Subpanel: Use 1 AWG Aluminum (Rated 100A in the 75°C column). If your load calculation exceeds 80A continuous, step up to 1/0 AWG.
- 150-Amp Service: Use 2/0 AWG Aluminum (Rated 135A at 75°C, wait—150A requires 3/0 AWG at 155A, or 2/0 if specific 310.12 dwelling allowances apply. Standard commercial requires 3/0 AWG).
- 200-Amp Residential Service: Use 4/0 AWG Aluminum. NEC 310.12 specifically permits 4/0 AL for 200A dwelling services, even though its 75°C rating is 180A.
Derating Factors: When the Chart Value Drops
The base values in the aluminum wire amp chart assume ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a single conduit. When real-world jobsite conditions deviate, you must apply derating multipliers to the 90°C column (yes, you use the 90°C column for the math, then compare the result to your termination limits).
1. Ambient Temperature Correction: If you are pulling aluminum SER cable through a hot attic in July where ambient temperatures reach 46°C-50°C (115°F-122°F), you must multiply the 90°C base ampacity by 0.82. For example, 2 AWG AL has a 90°C rating of 100A. Multiply by 0.82, and your true ampacity drops to 82A. You must then verify that 82A satisfies your termination requirements.
2. Conductor Bundling (More than 3 Current-Carrying Conductors): If you pull a multi-wire branch circuit or multiple feeders through the same PVC conduit, the heat generated by adjacent wires traps thermal energy. If you have 4 to 6 current-carrying conductors, apply an 80% multiplier. If you have 7 to 9 conductors, apply a 70% multiplier. (Note: Grounding wires and neutral wires carrying only unbalanced load do not count as current-carrying for this calculation).
What the Table Cannot Tell You:
The aluminum wire amp chart only addresses thermal limits of the insulation. It does not account for voltage drop. For any aluminum feeder run exceeding 100 feet, you must calculate voltage drop using the specific resistivity of aluminum (approx. 17 ohms per circular mil foot). A 2 AWG AL wire might be thermally rated for 90A, but over 150 feet, it will drop more than 3% of your voltage at that load, requiring you to upsize to 1/0 AWG or 2/0 AWG purely for performance. Furthermore, the chart doesn't tell you if the physical wire will fit into the breaker lug—always check the manufacturer's spec sheet for maximum lug wire ranges.
Aluminum Wire Amp Chart FAQ
Can I use the 90°C column for sizing my breaker?
No. While modern aluminum insulation like XHHW-2 and THHN is rated for 90°C, the lugs inside your breakers, disconnects, and panelboards are almost universally rated for 75°C (or 60°C for older/smaller panels). Per NEC 110.14(C), the weakest link in the thermal chain dictates the rule. You use the 90°C column exclusively as a starting point for derating math, but your final breaker size cannot exceed the 60°C or 75°C column limits.
What size aluminum wire do I need for a 100-amp subpanel?
For a standard 100-amp subpanel feeder, you need 1 AWG aluminum if the panel terminations are rated for 75°C (which most modern panels are). If you are using older equipment strictly limited to the 60°C column, you must upsize to 1/0 AWG aluminum to hit the 100A mark. Always use a 4-wire feed (two hots, one neutral, one ground) and keep the neutral and ground bars isolated in the subpanel.
Why is my aluminum wire ampacity lower than copper for the same AWG?
Aluminum has a higher electrical resistivity than copper—roughly 1.6 times higher. This means an aluminum conductor generates more heat (I²R losses) than a copper conductor of the exact same physical diameter when carrying the same current. To compensate, aluminum wire must be physically larger (typically two AWG sizes up) to match the ampacity and voltage drop characteristics of copper. For example, 2 AWG Copper carries 115A (75°C), while you need 1/0 AWG Aluminum to carry 120A (75°C).
Does the aluminum wire amp chart apply to underground direct burial cables?
No. Table 310.16 applies to conductors in raceways (conduit) or cables like SER exposed to ambient air. If you are burying aluminum USE-2 or UF-B cables directly in the earth, you must use NEC Table 310.104 (formerly 310.15(B)(16) in older code cycles) which accounts for the thermal resistivity of soil. Earth acts as an insulator, trapping heat differently than ambient air, which alters the allowable ampacities for direct burial configurations.
