What is XHHW wire used for?

XHHW and XHHW-2 are used for service entrance conductors, feeders, sub-panel supplies, and large aluminum runs pulled through conduit. XLPE insulation is tougher and more heat stable than the PVC used on THHN, which suits heavy pulls and hot environments.

What is the difference between XHHW and XHHW-2?

The -2 suffix means 90°C in wet locations as well as dry. Plain XHHW is 90°C dry but only 75°C wet. XHHW-2 is what is normally stocked and is required for any underground or wet location run where you want the 90°C derating basis.

Is XHHW better than THHN?

For large feeders and services, generally yes — XLPE insulation is tougher, more heat stable, and slightly smaller in sizes 4 AWG and up. For small conduit runs THHN is easier to pull thanks to its nylon jacket and takes less conduit space below 4 AWG.

Can XHHW be direct buried?

No. Like THHN, XHHW is a single conductor that must be installed in a raceway. XHHW-2 is rated for the wet conditions inside a buried conduit, but direct burial without a raceway requires USE-2 or UF-B.

XHHW and XHHW-2 Wire — Specifications, Ampacity and Uses

XHHW is Cross-linked High Heat-resistant Water-resistant wire: a single 600 V conductor insulated with cross-linked polyethylene (XLPE) instead of PVC, and with no nylon jacket. XHHW-2 adds a 90°C rating in wet locations as well as dry. It is the standard choice for large feeders, service entrances, and aluminum conductors above 1/0.

XHHW / XHHW-2 — Specifications

Property	Value
Voltage rating	600 V
Temperature rating (dry)	90°C
Temperature rating (wet)	75°C for XHHW, 90°C for XHHW-2
Insulation	Cross-linked polyethylene (XLPE), no nylon jacket
Conductor	Copper or aluminum, stranded
Sizes	14 AWG through 2000 kcmil
NEC article	Article 310, Table 310.4(A)
Direct burial	Not permitted as a bare conductor — requires a raceway
Flame rating	Passes the vertical flame test; permitted inside buildings
Typical use	Feeders, services, large aluminum runs, solar combiner wiring

Specifications reflect the common commercial product and the governing NEC article. Always confirm the markings printed on the conductor or jacket, which are the authoritative statement of what a given reel is listed for.

XHHW / XHHW-2 Ampacity — Copper, 75°C Column of NEC Table 310.16

Size	Ampacity
14 AWG	20 A
12 AWG	25 A
10 AWG	35 A
8 AWG	50 A
6 AWG	65 A
4 AWG	85 A
3 AWG	100 A
2 AWG	115 A
1 AWG	130 A
1/0 AWG	150 A
2/0 AWG	175 A
3/0 AWG	200 A
4/0 AWG	230 A

Copper conductors, 30°C ambient, not more than three current-carrying conductors. Correct for higher ambients and larger conductor counts with NEC Table 310.15. NEC 240.4(D) still caps 14, 12 and 10 AWG copper at 15, 20 and 30 A of overcurrent protection.

XHHW versus THHN

Both are 600 V, both are 90°C in the -2 versions, and both need a raceway. The difference is the insulation chemistry, and it shows up in three places.

Size. XHHW has no nylon jacket but thicker primary insulation in small sizes, so 14 through 10 AWG XHHW is physically larger than THHN — 12 AWG XHHW is 0.0181 in² against 0.0133 in² for THHN, so fewer fit in a conduit. From 4 AWG upward the relationship reverses and XHHW is slightly smaller. See the conduit fill charts, which list both.

Pulling. The nylon jacket on THHN is slippery, which makes long conduit pulls easier in small sizes. XLPE has a higher coefficient of friction but is much tougher and far more resistant to cracking at low temperature, which is why it wins on large, heavy feeder pulls.

Heat and moisture. XLPE is thermoset rather than thermoplastic: it does not soften and deform when hot the way PVC does. That makes XHHW-2 the better conductor for sustained high-temperature service and for wet locations over long service lives.

Where XHHW-2 is normally specified

Service entrance and feeder conductors above about 1/0, where the toughness of XLPE matters on a heavy pull and the slightly smaller diameter helps with conduit fill and lug fit.

Aluminum conductors generally. Most aluminum building wire above 1/0 — including the conductors inside SER and SEU cable — is XHHW-2 insulated.

Photovoltaic and battery systems, switchgear, and industrial installations where the ambient runs hot and the wet-rated 90°C figure is genuinely used for derating rather than as a formality.

Other Wire Types

THHN / THWN-2 Romex (NM-B)XHHW / XHHW-2 USE-2 UF-B SOOW / SJOOW Welding Cable Speaker Wire

THHN / THWN-2 wire →USE-2 direct burial conductor →Conduit fill charts →NEC Table 310.16 — conductor ampacity →Copper vs aluminum →