For standard residential and commercial wiring, the authoritative aluminum amp chart is governed by NEC Table 310.16 (formerly 310.15(B)(16)). If you need a direct answer for the most common service sizes: a 2/0 AWG aluminum wire is rated for 135 amps (75°C column) and is the standard choice for 100A subpanels, while 4/0 AWG aluminum is rated for 180 amps (75°C column) and is the standard for 200A residential services. However, the raw numbers in the chart are only the starting point; your final allowable ampacity is strictly limited by termination temperatures and environmental derating.

The Master Aluminum Amp Chart (NEC Table 310.16)

Before pulling wire, you need to know how to read the table. The rows represent the wire size in American Wire Gauge (AWG) or thousand circular mils (kcmil). The columns represent the temperature rating of the wire's insulation. The values inside are the maximum allowable ampacities for three current-carrying conductors in a raceway or cable, at an ambient temperature of 30°C (86°F).

Table 310.16: Allowable Ampacities of Insulated Aluminum Conductors (Rated 0-2000 Volts)
Wire Size (AWG/kcmil) 60°C Column (THW, THWN) 75°C Column (THHN, XHHW) 90°C Column (THHN, XHHW-2)
8 AWG30A40A45A
6 AWG40A50A55A
4 AWG55A65A75A
3 AWG65A75A85A
2 AWG75A90A100A
1 AWG85A100A115A
1/0 AWG100A120A135A
2/0 AWG115A135A150A
3/0 AWG130A155A175A
4/0 AWG150A180A205A
250 kcmil170A205A230A

Source: NFPA 70 (National Electrical Code), Table 310.16. Always verify against the specific edition adopted by your local AHJ.

Bookmark Quick-Jump Rows:
  • 100A Subpanel Feeder: Look at 2/0 AWG (135A in the 75°C column). While 1/0 AWG is rated 120A, 2/0 is heavily preferred to mitigate voltage drop and provide a safety margin.
  • 200A Main Service: Look at 4/0 AWG (180A in the 75°C column). This is the universal standard for 200A residential service entrance cable (SER).
  • 50A Hot Tub / EV Charger: Look at 4 AWG (65A in the 75°C column) or 2 AWG for longer runs.

Which Column Applies to Your Installation?

The most common mistake DIYers and junior electricians make is looking at the 90°C column because they bought 90°C THHN wire, and assuming they can push the wire to that limit. In almost all real-world scenarios, you must use the 75°C or 60°C column.

This is dictated by NEC 110.14(C) - Termination Provisions. The rule states that your system's ampacity is limited by the lowest temperature rating of any connected component. Modern breakers, panelboard lugs, and disconnect switches are typically tested and rated for 75°C terminations. Therefore, even if your aluminum wire has 90°C XHHW-2 insulation, the breaker lug is only good for 75°C.

Here is the practical decision framework for column selection:

  • Use the 60°C Column: For circuits rated 100 amps or less, or for wire sizes 14 AWG through 1 AWG, unless the equipment is specifically marked otherwise. (Many older panels and specific receptacles fall here).
  • Use the 75°C Column: For circuits rated over 100 amps, or wire sizes larger than 1 AWG. This is your default column for almost all aluminum feeder and service entrance work.
  • Use the 90°C Column: Only as a starting point for derating calculations (which we will cover next), or if the entire system—including wire, lugs, breakers, and splices—is explicitly rated and marked for 90°C, which is exceptionally rare in standard construction.

For a deeper dive into termination rules, manufacturer resources like Southwire's official ampacity guides provide excellent visual breakdowns of how insulation types map to these temperature columns.

How Derating Modifies the Base Ampacity

The numbers in the aluminum amp chart assume ideal conditions: exactly three current-carrying conductors in a conduit, and an ambient temperature of 30°C (86°F). When your installation deviates from this, you must apply derating factors.

Crucially, derating math is always performed using the 90°C column, regardless of your termination limits. Once you calculate the derated value, you compare it to the 75°C (or 60°C) termination limit, and the lower of the two numbers becomes your final allowable ampacity.

Real-World Derating Example: 4/0 Aluminum in a Hot Attic

Imagine you are running a 200A feeder using 4/0 AWG aluminum THHN (90°C rated) through an attic that reaches 110°F (43°C), and you are pulling 4 current-carrying conductors in the same conduit.

  1. Base Ampacity (90°C column): 205A.
  2. Ambient Temperature Correction: At 110°F, the NEC correction factor for 90°C wire is 0.91.
    205A × 0.91 = 186.55A.
  3. Bundling Adjustment: 4 current-carrying conductors require an 80% adjustment factor (0.80).
    186.55A × 0.80 = 149.24A.
  4. Final Comparison: Your derated 90°C capacity is 149A. Your 75°C termination limit (from the chart) is 180A. The lower number wins. Your final allowable ampacity is 149 amps.
Safety Warning: Because 149A is below the 200A breaker size, this installation would fail inspection and risk melting the wire insulation under full load. You must upsize the wire to 250 kcmil or 300 kcmil aluminum and recalculate, or reroute the conduit outside the hot attic space.

What Counts as a "Current-Carrying" Conductor?

When counting conductors for bundling derating, remember that equipment grounding conductors (EGCs) do not count. In a standard single-phase 120/240V split-phase feeder (two hots, one neutral, one ground), the neutral carries unbalanced current and does count as a current-carrying conductor. Therefore, you have 3 current-carrying conductors, meaning no bundling derating is required for a standard residential feeder.

What This Aluminum Amp Chart Cannot Tell You

While NEC Table 310.16 is the legal baseline for thermal safety, it does not guarantee a functional or code-compliant installation on its own. You must account for three physical realities that the chart ignores.

1. Voltage Drop Over Distance

The amp chart only tells you the wire's ability to dissipate heat; it does not account for resistance over length. Aluminum has roughly 61% higher electrical resistance than copper by volume. NEC Informational Note 310.15(B) recommends keeping voltage drop under 3% for branch circuits and 5% for the total system. If you are running a 2/0 aluminum feeder 150 feet to a detached garage for a 100A subpanel, the voltage drop will exceed 3%. You will need to upsize to 4/0 or 250 kcmil aluminum strictly for voltage drop mitigation, even though 2/0 is thermally rated for the load.

2. Physical Lug Fit and Termination Prep

Aluminum expands and contracts more than copper under thermal cycling, and it oxidizes rapidly when exposed to air. The amp chart assumes a perfect connection. In practice, you must use lugs explicitly marked AL/CU and apply an anti-oxidant compound (like Noalox or Ideal EJC) to the stripped aluminum strands before torquing the lug to the manufacturer's specified inch-pound rating. Failing to do this creates a high-resistance joint that will overheat, regardless of the wire's baseline ampacity.

3. Local AHJ Overrides

The NEC is a model code. Your local Authority Having Jurisdiction (AHJ) or municipal inspector has the final legal say. Some jurisdictions mandate copper for specific underground service laterals, ban aluminum branch wiring entirely, or require specific insulation types (like XHHW-2 instead of THHN) for wet locations. Always check with your local building department before purchasing hundreds of feet of aluminum SER or MH feeder cable based solely on a national reference chart.