For standard residential and commercial installations terminating on 75°C rated equipment, #2 AWG copper wire has an ampacity of 115 amps, and #2 AWG aluminum wire has an ampacity of 90 amps. These values assume an ambient temperature of 30°C (86°F) and no more than three current-carrying conductors in a raceway or cable, per the National Electrical Code (NEC).
While those are the baseline numbers, pulling the wrong breaker or misapplying the temperature column can result in a failed inspection or a melted termination lug. Below is the complete reference data, derating math, and a decision path to lock in your exact wire and breaker combination.
The #2 AWG Ampacity Reference Table (NEC Table 310.16)
This table is extracted directly from NEC Table 310.16 (2023/2026 editions). It lists the allowable ampacities for insulated conductors rated up to 2000 volts.
| Conductor Material | 60°C Column (140°F) | 75°C Column (167°F) | 90°C Column (194°F) |
|---|---|---|---|
| #2 AWG Copper | 95 Amps | 115 Amps | 130 Amps |
| #2 AWG Aluminum | 75 Amps | 90 Amps | 100 Amps |
Bookmark this row: For 95% of modern panelboards, breakers, and subpanel lugs, you will default to the 75°C column. The 90°C column is generally only used as a starting point for calculating derating adjustments, not for final breaker sizing.
Which Temperature Column Applies to Your Installation?
The most common mistake DIYers and junior apprentices make is looking at the 90°C column because THHN/THWN-2 wire is rated for 90°C, and then sizing the breaker to that higher number. This violates NEC 110.14(C) regarding termination provisions.
Your allowable ampacity is bottlenecked by the lowest temperature rating in the entire circuit loop. This includes the wire insulation, the breaker terminals, the panelboard bus bars, and the destination lugs.
- The 60°C Column: Applies to older homes with legacy equipment, NM-B (Romex) cable (which is internally limited to 60°C regardless of the wire's printed jacket rating), and circuits rated 100A or less where the termination temperature is unmarked.
- The 75°C Column: The modern standard. Almost all breakers and lugs manufactured in the last 30 years are rated for 75°C. If you are pulling individual THHN/THWN-2 conductors in conduit to a modern subpanel, this is your governing column.
- The 90°C Column: Used exclusively for ambient temperature corrections and conductor bundling derating. You can start your math here, but your final adjusted ampacity cannot exceed the 75°C (or 60°C) termination limit.
How Derating Modifies Your Base Ampacity
The baseline numbers in Table 310.16 assume you have 86°F (30°C) ambient air and no more than three current-carrying conductors (CCCs) bundled together. When you exceed these conditions, the wire cannot dissipate heat as efficiently, and you must apply derating factors.
Let's run a concrete numeric example for a solar or HVAC run using #2 AWG Copper THHN in a hot attic:
- Base Value: #2 Cu THHN in the 90°C column = 130A.
- Ambient Correction: The attic reaches 110°F (43°C). Per Table 310.15(B)(1), the correction factor for 90°C wire at 110°F is 0.87. (130A × 0.87 = 113.1A).
- Bundling Adjustment: You have 4 current-carrying conductors in the conduit. Per Table 310.15(C)(1), the adjustment factor is 80%. (113.1A × 0.80 = 90.48A).
- Termination Check: Your final derated value is 90.48A. Because this is lower than the 75°C termination limit (115A), the derated value governs.
Result: Your #2 AWG copper wire is now legally limited to 90 amps. You must protect it with a maximum 90A breaker (or the next standard size down, which is 80A, depending on continuous load rules).
Decision Path: Sizing Your Breaker and Application
Use this decision tree to lock in your exact material and breaker size for common #2 AWG applications. This eliminates the 'it depends' guesswork.
| Your Goal | Wire Material | Governing Column | Concrete Pick (Wire + Breaker) |
|---|---|---|---|
| Feed a 100A Subpanel | Aluminum (SER) | 75°C | FAIL. #2 AL is only 90A. Upgrade to #1 AL (100A) with a 100A breaker. |
| Feed a 90A Subpanel | Aluminum (SER) | 75°C | #2 AL wire on a 90A breaker. |
| 115A Continuous Feeder | Copper (THHN) | 75°C | #2 Cu wire on a 110A breaker (next standard size down, as 115A breakers are rare/specialty). |
| High-Current EV Charger | Copper (THHN) | 75°C | #2 Cu wire on a 100A breaker (allowing 80A continuous charging). |
| Welding Receptacle (60A) | Copper (NM-B) | 60°C | Overkill. #2 Cu NM-B is 95A. Downsize to #6 Cu NM-B (55A/60A) to save money and ease bending. |
What the Ampacity Table Cannot Tell You
While NEC Table 310.16 dictates thermal limits (how much current the wire can handle before the insulation melts), it completely ignores voltage drop and physical installation limits.
1. Voltage Drop Over Distance
Ampacity assumes the wire is infinitely short. In reality, wire has resistance. If you are pushing 90 amps through #2 AWG aluminum on a 240V circuit, you will hit a 3% voltage drop (the recommended maximum for branch circuits and feeders) at approximately 135 feet. If your subpanel is 200 feet away, #2 AWG is thermally safe but electrically inadequate. You must upsize to #1/0 AWG aluminum to maintain voltage stability, even if your breaker is only 90A. For exact calculations, use the voltage drop formulas outlined by EC&M and Mike Holt.
2. Physical Bending Radius and Conduit Fill
#2 AWG wire is thick, stiff, and unforgiving. If you are pulling three #2 AWG THHN conductors plus a #6 AWG ground, you need a minimum of 1.25-inch PVC or EMT conduit to stay under the 40% conduit fill rule. Furthermore, #2 wire requires a much larger bending radius at the panel. If you are working in a shallow 4-inch junction box or a cramped panelboard, you will physically struggle to seat the breakers and close the dead front. In tight spaces, consider using flexible SER cable where code permits, or upsizing the enclosure.
Final Default Recommendation: If you are wiring a standard detached garage subpanel up to 120 feet away, buy #1/0 AWG Aluminum SER cable and protect it with a 100A breaker. It costs only marginally more than #2 AL, guarantees a full 100A capacity without termination temperature violations, and absorbs voltage drop for typical garage loads.
