10 AWG Wire — Ampacity, Uses & Specifications

By PES Supply Technical Team — Last updated July 31, 2026

10 AWG wire is the workhorse of residential and light commercial solar PV wiring. It is used for **PV source circuits** connecting solar panels to combiner boxes, PV output circuits to string inverters, and residential AC feeders. USE-2 and PV Wire in 10 AWG are the standard conductor sizes for most residential rooftop solar installations. 10 AWG is also used for water heater circuits, air conditioning disconnects, and EV charging station wiring.

10 AWG wire has a cross-sectional area of 10.38 kcmil (5.26 mm²) with a conductor diameter of 0.1019 inches (2.588 mm). The copper weight is approximately 31.4 lbs per 1,000 feet, with a DC resistance of 0.999 Ω/1,000 ft for copper and 1.6 Ω/1,000 ft for aluminum at 75°C.

The following ampacity values are from NEC Table 310.16 (formerly Table 310.15(B)(16)), which provides allowable ampacities of insulated conductors rated up to 2000V. Ampacity is the maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

Important: The 90°C ampacity column may only be used for derating purposes (e.g., temperature correction and conduit fill adjustment). The actual circuit ampacity is limited by the equipment terminal rating — typically 75°C for equipment rated 100A or greater, and 60°C for equipment rated less than 100A per NEC 110.14(C).

Solar photovoltaic (PV) installations are governed by NEC Article 690, which has specific requirements for conductor sizing, temperature correction, and overcurrent protection that go beyond general wiring rules. 10 AWG wire is commonly used in PV systems for source circuits, output circuits, and interconnection wiring.

For PV source and output circuits, NEC 690.8(A) requires that conductors be sized to carry not less than 125% of the continuous current. This accounts for the fact that PV circuits can operate at maximum current for extended periods:

• PV Source Circuit Current: The rated Isc (short-circuit current) of the PV module × 1.25 (NEC 690.8(A)(1)(1))
• PV Output Circuit Current: The rated Isc of the PV array × 1.25 (NEC 690.8(A)(1)(2))
• Conductor Ampacity: Must be ≥ 125% of the calculated circuit current after applying all correction factors (NEC 690.8(B))

For example, if 10 AWG THHN-2/PV Wire is rated at 40A at 90°C, the maximum continuous PV circuit current is 40A × 0.80 = 32A (after applying the 125% continuous current factor).

PV conductors often operate in high ambient temperatures, especially on rooftops. NEC Table 310.15(B)(1) provides correction factors that reduce ampacity at elevated temperatures. For rooftop installations where conductors are within 0.5 inches of the roof surface, add 33°C (91°F) to the ambient temperature per NEC 310.15(B)(2).

Example: A 10 AWG THHN-2 PV Wire rated at 40A at 90°C, installed on a rooftop at 40°C ambient + 33°C rooftop adder = 73°C, has a correction factor of 0.58. Adjusted ampacity = 40A × 0.58 = 23A. After the 125% continuous current requirement: maximum PV circuit current = 18A.

NEC 690.31(C) requires that PV source and output circuit conductors use one of the following wire types:

• USE-2 — Underground Service Entrance cable, 90°C wet/dry, sunlight-resistant
• PV Wire — Specifically rated for PV applications, 90°C wet/dry, 600V or 2000V, sunlight-resistant, direct burial, improved flame resistance
• XHHW-2 — Cross-linked polyethylene, 90°C wet/dry, may be used in raceways
• THWN-2 — Thermoplastic heat and moisture resistant nylon, 90°C wet/dry, may be used in raceways

PV Wire and USE-2 are the preferred types for exposed rooftop wiring, as they are rated for sunlight resistance and the harsh thermal environment near solar modules. THHN/THWN-2 is acceptable when installed in conduit.

Proper installation of 10 AWG conductors requires compliance with NEC Article 300 (Wiring Methods) and NEC Article 310 (Conductors for General Wiring). These articles cover conduit fill, bending radius, support spacing, and physical protection requirements.

NEC Chapter 9 Table 1 specifies maximum conduit fill percentages: 53% for 1 conductor, 31% for 2 conductors, and 40% for 3 or more conductors. The following table shows typical EMT conduit sizes for 10 AWG THHN/THWN-2 conductors:

Note: Conduit fill values are approximate for THHN/THWN-2 copper conductors in EMT. Always verify with NEC Chapter 9 Tables 4 and 5 for your specific wire type and conduit material. When more than 3 current-carrying conductors are installed in the same conduit, ampacity must be derated per NEC Table 310.15(C)(1).

NEC 300.34 requires that conductors not be bent to a radius less than 8 times the overall diameter of the conductor or cable. For 10 AWG wire with an approximate diameter of 0.1019" (stranded), the minimum bending radius is:

• Single conductor: 8 × 0.1019" = 0.82" minimum bend radius
• In conduit: The conduit bending radius must meet NEC Table 2 (Chapter 9) requirements based on conduit size, which is typically more restrictive than the conductor bending radius

Conductors in raceways are supported by the conduit system itself. For cable assemblies (such as MC cable or NM-B in 10 AWG), support spacing requirements include:

• MC Cable: Secured every 6 feet and within 12 inches of each box, fitting, or termination (NEC 330.30)
• NM-B (Romex): Secured every 4.5 feet and within 12 inches of boxes (NEC 334.30)
• Conduit (EMT): Supported every 10 feet and within 3 feet of boxes/terminations (NEC 358.30)
• Conduit (RMC): Supported every 10 feet and within 3 feet of boxes/terminations (NEC 344.30)

NEC 300.4 requires physical protection of conductors and cables:

• Through studs/joists: Bored holes must be at least 1.25 inches from the edge of the framing member, or protected with a steel plate at least 1/16 inch thick
• Exposed to damage: Cables passing through floor/ceiling must be protected by guard strips at least as tall as the cable
• Underground: Direct-buried conductors must be at the depths specified in NEC Table 300.5 — minimum 24 inches for direct-burial cables (18 inches for residential branch circuits with GFCI protection)
• In wet locations: Raceways must be arranged to prevent moisture entry; drain points should be provided at low points in the run

When more than 3 current-carrying conductors are installed in the same raceway or cable, the ampacity must be reduced per NEC Table 310.15(C)(1) (formerly 310.15(B)(3)(a)):

• 4–6 conductors: 80% ampacity
• 7–9 conductors: 70% ampacity
• 10–20 conductors: 50% ampacity
• 21–30 conductors: 45% ampacity
• 31–40 conductors: 40% ampacity
• 41+ conductors: 35% ampacity

Neutral conductors carrying harmonic currents (non-linear loads) are counted as current-carrying conductors. Equipment grounding conductors are not counted.

Voltage drop is a critical consideration in conductor sizing. The NEC recommends a maximum voltage drop of 3% on feeders and 5% total (feeder + branch circuit) for efficient operation. For solar PV circuits, voltage drop directly affects system yield — every 1% of voltage drop represents approximately 1% power loss.

Calculations based on copper conductor resistance of 0.999 Ω/1000 ft at 75°C operating temperature. Values assume single-phase AC or DC circuits (2 conductors). For three-phase circuits, multiply voltage drop by 0.866.

Calculate voltage drop for 10 AWG copper wire based on your specific circuit parameters. This calculator uses the standard voltage drop formula: VD = 2 × R × I × L ÷ 1000, where R is conductor resistance per 1000 ft, I is current in amps, and L is one-way circuit length in feet.

PES Supply carries 50,000+ SKUs from 169 authorized brands. Browse our selection of 10 AWG wire and cable products below, or explore our complete Wire & Cable collection for the full inventory.

Don't see what you need? We stock THHN, THWN-2, XHHW-2, USE-2, PV Wire, MC Cable, and bare copper in all AWG sizes. Browse all wire & cable → or contact our team for custom quotes.

Disclaimer: This guide is for informational purposes and is based on the 2023 National Electrical Code (NEC). Always consult the current NEC and local codes, and work with a licensed electrician. Ampacity values reference NEC Table 310.16. PES Supply is not liable for installation errors or code violations.