The Quick Answer: 2/0 AWG Wire Amp Rating

When sizing conductors for heavy feeders or service entrances, the 2/0 AWG wire amp rating depends entirely on the conductor material and the temperature rating of your terminations. For standard residential and commercial installations governed by the National Electrical Code (NEC), here are the baseline numbers you need to memorize:

  • Copper (75°C column): 175 Amps
  • Aluminum (75°C column): 135 Amps
  • Copper (90°C column, for derating only): 195 Amps
  • Aluminum (90°C column, for derating only): 150 Amps
Bookmark Quick-Jump: If you are pulling wire for a standard 200-amp residential main service, skip straight to the Dwelling Service Exception section below. The standard table ampacity does not apply to your project in the way you might think.

How to Read the NEC Ampacity Table for 2/0 Wire

To understand the exact current-carrying capacity (ampacity) of 2/0 AWG (often pronounced "two-aught"), we look to NEC Table 310.16. This table is the undisputed source of truth for conductor sizing in the United States.

When reading this table, you must track three variables: the metal (Copper vs. Aluminum), the insulation type (THHN, XHHW, etc.), and the temperature column (60°C, 75°C, or 90°C). Below is the extracted data specifically for 2/0 AWG conductors.

Conductor Material 60°C (140°F) 75°C (167°F) 90°C (194°F)
Copper (THHN, XHHW-2) 145 A 175 A 195 A
Aluminum (XHHW, THHN) 115 A 135 A 150 A

Source: NEC Table 310.16 (formerly 310.15(B)(16)). Values assume an ambient temperature of 30°C (86°F) and not more than three current-carrying conductors in a raceway.

Which Temperature Column Applies to Your Installation?

The most common mistake DIYers and junior apprentices make is looking at a spool of 90°C-rated THHN copper wire, seeing "195 Amps" on the spec sheet, and assuming they can protect it with a 200A breaker. This is a code violation and a fire hazard.

Under NEC 110.14(C), the ampacity of your wire is limited by the lowest temperature rating of any connected termination, device, or conductor in the circuit. This is known as the "weakest link" rule.

  • The 60°C Column: Applies to older equipment, NM-B (Romex) cable, and circuits rated 100A or less that do not have a marked temperature rating.
  • The 75°C Column: Applies to almost all modern breakers, panelboard lugs, and subpanel feeders rated over 100A. Even if your wire insulation is rated for 90°C, you must use the 75°C column to determine your final breaker size.
  • The 90°C Column: This column is only used as your starting baseline for calculating derating adjustments (like ambient heat or wire bundling). Once you apply the derating math, you compare the result to the 75°C column and use whichever is lower.

Derating and the "Dwelling Service" Exception

Baseline ampacity assumes perfect conditions: 86°F ambient air and a maximum of three current-carrying conductors in a conduit. Real jobsites rarely offer perfect conditions.

How Derating Modifies the Base Value

If you pull four or more current-carrying conductors through the same conduit, or if your attic ambient temperature exceeds 86°F, you must apply a correction factor from NEC Table 310.15(B)(1) and (C)(1).

Example: You are pulling four 2/0 AWG copper THHN wires (two hots, one neutral, one ground for a multi-wire branch circuit or specific feeder setup) through a conduit in a 110°F attic.

  1. Start with the 90°C column: 195A.
  2. Apply 4-conductor bundling derating (80%): 195 × 0.80 = 156A.
  3. Apply 110°F ambient correction (87%): 156 × 0.87 = 135.7A.
  4. Compare to the 75°C termination limit (175A). The derated value (135.7A) is lower, so your wire is now legally limited to 135 Amps.

What the Table Cannot Tell You: The 83% Dwelling Rule

If you are wiring a 200-amp main service for a single-family home, Table 310.16 will tell you that 2/0 Copper is only good for 175 Amps. However, NEC 310.12(A) provides a specific exception for single-phase dwelling services and feeders.

Because residential loads are highly diversified (you rarely run the oven, dryer, AC, and EV charger at maximum draw simultaneously), the NEC allows dwelling service conductors to be sized at 83% of the service rating.

  • 200A service × 0.83 = 166A required ampacity.
  • 2/0 AWG Copper (175A at 75°C) exceeds 166A. Therefore, 2/0 Copper is legally permitted for a 200A residential main service.
  • If using Aluminum, you must step up to 4/0 AWG Aluminum (205A at 75°C) to meet the 200A dwelling requirement.

Decision Path: Sizing Your 2/0 AWG Breaker and Lugs

Stop guessing and use this decision tree to finalize your materials list. This path assumes standard 60Hz AC power in a residential or light-commercial setting. For further verification on local amendments, always consult your local Authority Having Jurisdiction (AHJ) or a licensed master electrician, as local codes can supersede the NEC.

If Your Project Is... Then Use This Wire... Terminate With... Protect With (Breaker/Fuse)
200A Residential Main Service (Dwelling) 2/0 AWG Copper OR 4/0 AWG Aluminum 75°C rated main lugs (standard on 200A panels) 200 Amp Main Breaker
175A Subpanel Feeder (Non-dwelling or commercial) 2/0 AWG Copper 75°C rated feeder lugs 175 Amp Molded Case Breaker
150A Subpanel Feeder 1/0 AWG Copper OR 2/0 AWG Aluminum 75°C rated feeder lugs 150 Amp Breaker
High-Current DC Inverter Feed (e.g., 48V Solar/Battery) 2/0 AWG Copper (Fine-stranded flex) Crimped ring terminals, torqued to mfr spec 150A to 175A Class-T DC Fuse (placed within 7 inches of battery positive)
Final Torque Warning: 2/0 AWG wire requires significant mechanical force to seat properly. A loose lug on a 175A circuit will arc, oxidize, and melt the panel busbar. Always use a calibrated torque screwdriver or wrench set to the exact inch-pound value printed on the breaker or lug datasheet (typically between 250 and 400 in-lbs for 2/0 lugs, but verify the specific manufacturer's label).