Allied Encyclopedia: XHHW-2 Wire vs. THHN/THWN Wire

Allied EncyclopediaXHHW-2 Wire and THHN/THWN Wire are both categorized as building wire, and they share many features and ratings. These cables are approved for use in applications up to 600 volts, and are resistant to abrasion, heat and moisture. But how exactly do they differ? Whether you choose XHHW-2 or THHN/THWN depends on your desired price and insulation requirements.

XHHW-2 Wire

XHHW-2 cable is general purpose wiring, and is found in conduit, raceways, services, feeders, and branch circuits. It is also suitable for power distribution systems in industrial, commercial, and residential buildings.

XHHW-2 insulation is similar to XHHW, which stands for “XLPE (Cross-linked Polyethylene) High Heat-resistant Water-resistant.” XHHW-2 is rated for up to 90°C in dry or wet locations. XHHW is also a good choice for dry locations up to 90°C, but it is only recommended for 75°C wet. Because of its more desirable temperature rating, XHHW-2 has superseded the XHHW specification.


THHN, or “Thermoplastic High Heat-resistant Nylon-coated,” is another electrical wire that can be run through conduit. It features flame retardant Polyvinylchloride (PVC) insulation, and a Nylon coating protects it from gasoline and oil. Like XHHW-2, THHN cable is commonly used in general purpose applications. You can also use it as machine tool, control circuit or appliance wiring.

Type THHN can only be used in dry locations not exceeding 90°C.  Fortunately, many of these cables are now THHN/THWN dual rated, meaning they can also be used in wet locations up to 75°C. With a THWN-2 rating, you can achieve an even higher temperature rating of 90°C for both wet and dry locations.


The main difference between these two building wires is that XHHW-2 features XLPE insulation and THHN/THWN uses PVC. This difference in materials makes THHN/THWN cheaper in price. However, when burned, PVC can emit a toxic smoke, and because THHN/THWN is designed with a thinner PVC insulation, it is more susceptible to current leakage and eventual breakdown. The nylon coating used for THHN/THWN wire also decreases the cable’s pliability, making installation more difficult.

On the other hand, XHHW-2 features a more flexible design that is easier to install. XHHW-2 wire also features better low temperature and electrical properties than THHN/THWN wire, and it is the preferred choice of the two.

Both XHHW-2 wire and THHN/THWN wire can serve your electrical wire needs, but you should know the difference in cost, insulation and electrical properties before making any purchase. Search Allied Wire’s selection of XHHW and XHHW-2 wire or our large variety of THHN/THWN cable to learn more about the cables’ features and benefits, and to see which could be the better solution for your application.

About awcwire
Allied Wire & Cable is a value-added manufacturer and distributor of electrical wire and cable, tubing, and more. We are a family owned and operated company, serving a wide range of industries, including the military, automotive, aerospace, and telecommunications markets. Allied is headquartered in Collegeville, PA. Additional locations can be found across the US, in Phoenix, AZ; Bedford, NH; Pewaukee, WI; Rochester, NY, Tampa, FL; and Mt. Juliet, TN. For more information on Allied, visit our main website at

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