The Direct Answer: 1 AWG Ampacity at a Glance

For standard building wire, 1 AWG copper THHN has a maximum ampacity of 145 amps (90°C column) and 1 AWG aluminum XHHW-2 has a maximum ampacity of 115 amps (90°C column). However, because nearly all residential and commercial breakers and lugs are rated for 75°C terminations, your usable ampacity drops to 130 amps for copper and 100 amps for aluminum.

Bookmark-Friendly Quick Jump:
  • 1 AWG Copper (75°C Terminations): 130 Amps
  • 1 AWG Copper (90°C Derating Base): 145 Amps
  • 1 AWG Aluminum (75°C Terminations): 100 Amps
  • 1 AWG Aluminum (90°C Derating Base): 115 Amps
Mains Voltage Safety: Working with 1 AWG wire typically involves 100A to 125A feeder circuits. Always de-energize the upstream breaker, apply lockout/tagout, and verify the bus is dead with a tested CAT III or CAT IV multimeter before stripping insulation or torquing lugs. NEC-style guidance applies here; your local AHJ has final authority on permitted installations.

How to Read the NEC Table 310.16 Ampacity Chart

The National Electrical Code (NEC) Table 310.16 is the master reference for conductor sizing, but reading it blindly leads to tripped breakers or melted lugs. The table is divided into three temperature columns: 60°C, 75°C, and 90°C. Here is how to determine which column applies to your installation:

  1. The 75°C Column (Your Termination Limit): Per NEC 110.14(C), you must size your wire based on the lowest temperature rating of any connected device. Since standard 100A+ breakers, panelboard lugs, and disconnects are rated for 75°C, you must use the 75°C column to determine your final circuit ampacity.
  2. The 90°C Column (Your Derating Base): Modern insulation like THHN and XHHW-2 is rated for 90°C. You use this higher column only as the starting number when calculating derating adjustments for bundling or high ambient heat.
  3. The 60°C Column (Legacy & Small Circuits): You will rarely use this for 1 AWG wire. It applies to older NM-B (Romex) installations or circuits under 100A where equipment isn't explicitly marked with a temperature rating.

Complete 1 AWG Ampacity Reference Table

The following data is extracted directly from NEC Table 310.16 (2023/2026 editions) for ambient temperatures not exceeding 30°C (86°F). It covers the most common insulations you will pull through conduit for 1 AWG feeders.

Table 1: 1 AWG Conductor Ampacity by Material and Insulation (Source: NEC Table 310.16)
Conductor Material Insulation Type 60°C Column (Amps) 75°C Column (Amps) 90°C Column (Amps)
Copper TW / UF 110A - -
Copper THW / THWN / RHW - 130A -
Copper THHN / THWN-2 / XHHW - - 145A
Aluminum TW / UF 85A - -
Aluminum THW / THWN / RHW - 100A -
Aluminum XHHW-2 / THHN - - 115A

Note: The Copper Development Association notes that while copper offers higher conductivity per cross-sectional area, aluminum remains the dominant choice for feeder runs over 50 feet due to weight and cost advantages.

Derating 1 AWG Wire: When the Base Value Drops

The base values in Table 310.16 assume you have no more than three current-carrying conductors in a raceway and an ambient temperature of 30°C (86°F). When conditions change, you must apply adjustment factors from NEC 310.15. Crucially, derating calculations always start from the 90°C column, even if your terminations are 75°C.

Worked Example: Bundled Conductors in a Hot Attic

Imagine you are pulling four current-carrying conductors (two hots, one neutral, one ground is not counted) through an attic where the ambient temperature hits 45°C (113°F).

  • Step 1 (Base): 1 AWG Copper THHN = 145A (90°C column).
  • Step 2 (Bundling): 4 conductors requires an 80% adjustment factor (NEC Table 310.15(C)(1)). 145A × 0.80 = 116A.
  • Step 3 (Temperature): 45°C ambient requires an 87% correction factor (NEC Table 310.15(B)(1)). 116A × 0.87 = 100.9A.
  • Step 4 (Termination Check): Your final derated ampacity is 100.9A. Because 100.9A is less than the 130A limit of the 75°C termination column, the wire is legally permitted to carry 100A. You would protect this circuit with a 100A breaker.

Decision Path: Which 1 AWG Conductor Should You Pull?

Use this decision matrix to select the exact wire type and material for your specific jobsite conditions. Stop at the first condition that matches your project.

Table 2: 1 AWG Conductor Selection Decision Tree
If Your Installation Is... Then Pull This Exact Wire... Why This Wins
A 100A subpanel feeder (under 50 ft) 1 AWG Aluminum XHHW-2 Terminates perfectly at 100A (75°C). XHHW-2 has thinner insulation than THHN, making it much easier to pull through 1.25" conduit bends.
A 100A subpanel feeder (over 50 ft) 1/0 AWG Aluminum XHHW-2 1 AWG will suffer >3% voltage drop at 100A over 50ft. Bumping to 1/0 AWG (120A @ 75°C) solves the drop without changing conduit size.
A short, high-vibration run to a 125A motor 1 AWG Copper THHN/THWN-2 Copper handles vibration and fine-strand bending better. 130A ampacity at 75°C covers the 125A continuous load requirement.
Wet location / direct burial conduit 1 AWG Copper or Al THWN-2 / XHHW-2 The 'W' or 'W-2' suffix is mandatory for wet locations. Standard THW is insufficient for underground condensation.

What the Ampacity Table Cannot Tell You

While NEC Table 310.16 dictates thermal limits, it ignores physical and electrical realities that will ruin your installation if overlooked. Before ordering your 1 AWG wire, account for these three blind spots:

  1. Voltage Drop: Ampacity tables assume a zero-distance run. On a 240V circuit, a 1 AWG copper wire carrying 130A will drop roughly 3.2V per 100 feet. If your run exceeds 100 feet, you must upsize to 1/0 AWG or 2/0 AWG to maintain the NEC-recommended 3% maximum voltage drop for feeders.
  2. Conduit Fill and Bending Radius: 1 AWG wire is thick and stiff. Three 1 AWG THHN wires will max out a 1-inch PVC conduit (40% fill rule). If you need to add a ground wire or pull through tight sweeps, you must step up to 1.25-inch conduit. Furthermore, the NEC mandates a minimum bending radius of 8 times the conductor diameter for 1 AWG—meaning your sweeps must be wide and gradual to avoid kinking the insulation.
  3. Lug Torque Specifications: A 1 AWG wire seated in a 100A breaker lug requires precise mechanical pressure. Under-torquing creates a high-resistance joint that will arc and melt; over-torquing strips the aluminum threads on the breaker bus. Always use a calibrated digital torque screwdriver set to the exact lb-in value printed on the breaker's wiring diagram (typically between 25 and 45 lb-in for this size).
The Default Pick: If you are wiring a standard residential 100A detached garage subpanel and want a single, cost-effective, code-compliant answer: buy 1 AWG Aluminum XHHW-2. It hits exactly 100A in the 75°C termination column, costs roughly 40% less per foot than copper, and its thinner insulation makes conduit pulls significantly easier on your shoulders.