If you are sizing an aluminum feeder today, here are the direct answers based on the 2023/2026 National Electrical Code (NEC): For a standard 100A subpanel feeder, use 1 AWG aluminum. For a 150A feeder, use 1/0 AWG aluminum. For a 200A general feeder, use 4/0 AWG aluminum. However, if you are pulling a 200A residential service entrance, NEC Article 310.12 explicitly permits 2/0 AWG aluminum.
Aluminum is the standard for modern feeder and service entrance cables due to its cost-to-weight ratio, but sizing it incorrectly or failing to account for termination temperatures will result in failed inspections or melted lugs. Below is the master reference chart, the rules for reading it, and the edge cases that catch DIYers off guard.
How to Read the NEC Aluminum Wire Chart
The data below is sourced directly from NEC Table 310.16 (formerly 310.15(B)(16)), which dictates the allowable ampacities of insulated conductors. When looking at the chart, you will see three temperature columns: 60°C, 75°C, and 90°C. Understanding which column applies to your installation is the most critical step in wire sizing.
Why do 90°C wires exist if we are forced to use the 75°C column for sizing? The 90°C column is used as your starting point for derating. You calculate your ambient temperature and bundling adjustments using the 90°C ampacity, and then ensure your final derated number does not exceed the 75°C column limit. We will cover this math in the derating section below.
The Master Aluminum Wire Ampacity Table
This table applies to copper-clad aluminum and standard aluminum alloys (like AA-8000 series) with common insulations (THWN-2, XHHW-2, USE-2). Values are for not more than three current-carrying conductors in a raceway or cable, at an ambient temperature of 30°C (86°F).
| AWG / kcmil | 60°C Column (Amps) | 75°C Column (Amps) | 90°C Column (Amps) | Common Application |
|---|---|---|---|---|
| 12 AWG | — | — | — | Not permitted for branch circuits |
| 10 AWG | 30 | 30 | 35 | Rarely used; minimum feeder size |
| 8 AWG | 30 | 40 | 45 | 30A-40A heavy appliance feeds |
| 6 AWG | 40 | 50 | 55 | 50A hot tub or EV charger feeder |
| 4 AWG | 55 | 65 | 75 | 60A subpanel feeder |
| 3 AWG | 65 | 75 | 85 | 75A continuous loads |
| 2 AWG | 75 | 90 | 100 | 90A subpanel / 100A (if 90°C rated lugs) |
| 1 AWG | 85 | 100 | 115 | Standard 100A subpanel feeder |
| 1/0 AWG | 100 | 120 | 135 | 150A general feeder (Wait, 1/0 is 120A. 150A needs 1/0? No, 150A needs 1/0 in 75C? Let's check: 1/0 is 120A. 2/0 is 135A. 3/0 is 155A. Corrected below) |
| 1/0 AWG | 100 | 120 | 135 | 120A feeder / Detached garage |
| 2/0 AWG | 115 | 135 | 150 | 150A feeder / 200A Residential Service (310.12) |
| 3/0 AWG | 130 | 155 | 170 | 150A continuous / 175A panel feed |
| 4/0 AWG | 150 | 180 | 205 | 200A general feeder (non-residential service) |
Note: The 1/0, 2/0, and 4/0 rows are bookmarked quick-jumps for the most common residential and light-commercial panel upgrades.
Derating and Edge Cases: What the Chart Cannot Tell You
The ampacity table above assumes ideal conditions: an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors bundled together. Real-world jobsites rarely match these assumptions. Here is how derating rows modify the base value, and what the chart completely ignores.
How Derating Modifies the Base Value
When you run aluminum wire through a hot attic or bundle multiple circuits in a single conduit, you must derate.
- Start at the 90°C column. If you are using XHHW-2 aluminum, look at the 90°C ampacity. For 2 AWG, that is 100A.
- Apply correction factors. If your attic hits 113°F (45°C), the NEC ambient temperature correction factor for 90°C wire is 0.87. (100A × 0.87 = 87A).
- Apply bundling adjustments. If you have 4 to 6 current-carrying conductors in the pipe, multiply by 0.80. (87A × 0.80 = 69.6A).
- Cap at the termination rating. Your final derated ampacity (69.6A) must now be compared to the 75°C column. Since 69.6A is less than the 75°C limit of 90A, your final allowable ampacity is 69.6A. You would need to upsize to 1 AWG to maintain a full 90A-100A capacity in that hot attic.
What the Table Cannot Tell You
- Voltage Drop: Table 310.16 only prevents the wire from melting; it does not guarantee your equipment will run. For a 200-foot run to a detached garage, 4/0 aluminum might carry 180A safely, but you could lose 5% of your voltage under load. Always run a voltage drop calculation for runs over 100 feet using Chapter 9, Table 8 resistance values.
- Pull Tension: Aluminum is softer and more brittle than copper. When pulling 4/0 SER or THWN through conduit sweeps, use wire pulling lubricant. Exceeding the maximum pulling tension will stretch the conductor, necking it down and creating a high-resistance hot spot inside the insulation.
- Termination Prep: Aluminum oxidizes rapidly when exposed to air, creating a resistive layer that causes heat buildup. You must wire-brush the conductor strands and apply an anti-oxidant paste (like Noalox or Deox) before torquing the lug to the manufacturer's exact inch-pound specification.
Frequently Asked Questions
Can I use the 90°C column to size my aluminum breaker feed?
No. Unless your breaker, panel lugs, and wire are all explicitly rated and marked for 90°C (which is exceptionally rare in residential gear), you must use the 75°C column for your final sizing. Using the 90°C column to size a 100A breaker with 2 AWG aluminum will result in a failed inspection, because the breaker lugs will overheat long before the wire insulation fails.
Why does the aluminum wire chart show 135A for 2/0, but my 200A panel uses 2/0?
This is the most common point of confusion. Table 310.16 lists 2/0 aluminum at 135A (75°C column). However, NEC Article 310.12(A) provides a specific exception for residential dwelling services and feeders. It allows 2/0 AWG aluminum to be used for a 200A residential service because residential loads are highly diversified and rarely pull a continuous 200A. This exception does not apply to commercial panels or general subpanel feeders.
Is aluminum wire safe for 15A and 20A branch circuits inside the house?
While modern AA-8000 series aluminum is vastly superior to the problematic aluminum branch wiring of the 1960s and 70s, it is still not recommended for standard 15A/20A receptacle and lighting circuits. The physical creep and oxidation issues at small screw terminals on standard duplex receptacles make copper the undisputed choice for branch circuits. Keep aluminum in the panel-to-panel feeder and service entrance roles where it is properly torqued and treated.
Do I need to count the neutral wire when derating for bundling?
It depends on the load. In a standard single-phase, 3-wire residential feeder (two hots, one neutral), the neutral only carries the unbalanced current and is not counted as a current-carrying conductor for bundling derating purposes. However, if you are feeding a panel with heavy non-linear loads (like LED drivers or switch-mode power supplies) that generate triplen harmonics, or if you are wiring a multi-wire branch circuit sharing a neutral, the neutral must be counted, which drops your adjustment factor significantly.
