XHHW Wire

Q: What does XHHW-2 stand for?

XHHW-2 stands for Cross-linked polyethylene, High Heat-resistant, Water-resistant, 90°C wet rated. The "X" indicates cross-linked polyethylene (XLPE) insulation, "HH" means 90°C dry rating, "W" means wet-location approved, and "2" means the 90°C rating applies in wet locations as well.

Q: Is XHHW-2 better than THHN?

XHHW-2 has advantages over THHN in wet locations — it maintains its full 90°C rating when wet, while THHN drops to 75°C. XHHW-2 insulation is also more resistant to chemicals and physical damage. However, for standard dry residential work, THHN is equally capable and more widely available. XHHW-2 is preferred for industrial, underground-in-conduit, and high-temperature applications.

XHHW stands for Cross-linked polyethylene High Heat-resistant Water-resistant. Superior chemical and moisture resistance. Thicker insulation. Better for harsh environments.

Dry rating90°C

Wet rating75°C

Voltage600V

Locationsdry, damp, wet

Specifications

Property	Value
Full name	Cross-linked polyethylene High Heat-resistant Water-resistant
Insulation material	XLPE (thermoset, cross-linked)
Outer covering	None
Temperature rating (dry)	90°C (194°F)
Temperature rating (wet)	75°C (167°F)
Voltage rating	600V
Approved locations	dry, damp, wet

Advantages and limitations

Advantages: Better chemical/ozone resistance, more durable, less dielectric leakage, no toxic smoke when burned.

Limitations: Thicker = less conduit fill. More expensive. Harder to strip.

Ampacity by gauge

The table below shows NEC Table 310.16 ampacity for XHHW conductors. Values shown reflect the 110.14(C) termination temperature limit, which determines the real-world usable ampacity - not just the insulation rating. Click any gauge to see the full derating chain.

Gauge	Copper	Aluminum
14 AWG	See page	-
12 AWG	See page	See page
10 AWG	See page	See page
8 AWG	See page	See page
6 AWG	See page	See page
4 AWG	See page	See page
3 AWG	See page	See page
2 AWG	See page	See page
1 AWG	See page	See page
1/0 AWG	See page	See page
2/0 AWG	See page	See page
3/0 AWG	See page	See page
4/0 AWG	See page	See page

When to use XHHW wire

Superior chemical and moisture resistance. Thicker insulation. Better for harsh environments.

Common applications for XHHW:

High-temperature environments - rated 90°C even in wet locations, superior to THHN in damp conditions
Industrial and commercial feeders - cross-linked polyethylene insulation resists chemical and physical damage
Switchgear connections - preferred where heat from adjacent conductors is a concern
Underground in conduit - "W" rating permits direct exposure to moisture without additional protection

NEC code references for XHHW

The NEC defines wire insulation types in Table 310.4(1) (formerly Table 310.104(A)). Key sections that apply:

Table 310.4(1) - lists XHHW with its temperature rating, insulation material, and approved locations
Table 310.16 - ampacity values for conductors in raceway, cable, or earth (the values shown in our ampacity table above)
Section 110.14(C) - termination temperature limits that determine real-world usable ampacity
Section 310.15(C)(1) - adjustment factors for more than 3 current-carrying conductors in a raceway

Frequently asked questions about XHHW wire

What does XHHW-2 stand for?

XHHW-2 stands for Cross-linked polyethylene, High Heat-resistant, Water-resistant, 90°C wet rated. The "X" indicates cross-linked polyethylene (XLPE) insulation, "HH" means 90°C dry rating, "W" means wet-location approved, and "2" means the 90°C rating applies in wet locations as well.

Is XHHW-2 better than THHN?

XHHW-2 has advantages over THHN in wet locations - it maintains its full 90°C rating when wet, while THHN drops to 75°C. XHHW-2 insulation is also more resistant to chemicals and physical damage. However, for standard dry residential work, THHN is equally capable and more widely available. XHHW-2 is preferred for industrial, underground-in-conduit, and high-temperature applications.

Can XHHW-2 be used in residential wiring?

Yes - XHHW-2 is fully approved for residential use in conduit. However, it is less common than THHN in residential work because THHN is more widely available and less expensive. Both have identical ampacity values in dry locations. XHHW-2 is more common in commercial and industrial installations.

Other wire insulation types

THHN 90°C THWN 75°C THWN-2 90°C XHHW-2 90°C RHH 90°C RHW-2 90°C USE-2TW 60°C NM-B 60°C UF-B 60°C MC Cable 90°C AC Cable (BX) 90°C SER/SEU 75°C PV Wire 90°C THHW 90°C THW 75°C THW-2 90°C RHW 75°C MI 90°C UF 60°C XHH 90°C FEP 90°C SIS 90°C

Requirements vary by state. NEC edition, licensing, permits, and GFCI rules differ by jurisdiction. Check your state or pick it below for personalized info across WireRef.

Important: For reference only. Not a substitute for a licensed electrician. Electrical work can cause serious injury, death, fire, or property damage if performed incorrectly. Always hire a licensed electrician for electrical work, especially for service upgrades, panel work, and 240V circuits. Values are derived from NFPA 70 (NEC) for educational purposes. Always verify against your locally adopted NEC edition and amendments - local jurisdictions may enforce stricter requirements. WireRef provides reference information only and is not responsible for work performed based on this content. NEC® is a registered trademark of the National Fire Protection Association. Free NEC access via NFPA · OSHA Electrical Safety · Terms of use.

NEC 2023 references verified April 2026