Southwire 63948426 10/3WG 100-Foot NMB Wire

The Verdict

If you’re wiring a 30-amp circuit — an EV charger, a subpanel, a water heater, or a dryer — you’ve likely stared at the copper wire aisle wondering if you’re overpaying for a brand name. The Southwire 63948426 10/3WG is the wire electricians reach for when they want to finish a job without wrestling with junk. Here’s what you’re actually getting for that premium.

What’s in the Box

This is a 100-foot coil of NM-B (non-metallic sheathed) cable, commonly called Romex — though Romex is technically a brand name owned by Southwire’s competitor. You’re getting three 10 AWG stranded copper conductors (black, red, white) plus a bare copper ground. The 10/3 designation means three insulated conductors plus ground. The jacket is a gray PVC rated for 600 volts, and the cable is rated for 90°C conductor temperature, though your breaker and termination points will dictate the actual ampacity (typically 30 amps for this configuration).

The spool itself is well-wound — no bird’s nests or tangles when you pull it from the box. As shown in the product image, the jacket is smooth and uniformly extruded, without the thin spots or bulges you see on budget cable.

Performance and Build Quality

Stranded 10 AWG is the standout feature here. Unlike solid wire, which fights you around bends and can work-harden and snap if you bend it too many times, this stranded copper pulls through conduit and flexes around studs with reasonable effort. The insulation strips cleanly with a standard wire stripper, and the copper is bright and corrosion-free — a sign of quality refining, not recycled scrap.

The jacket is thick enough to resist nicks from cable staples but not so thick it’s a struggle to strip. Multiple buyers noted the cable measures out to a true 100 feet, which matters when you’re planning a long run and don’t want to discover you’re short at the last junction box.

What Buyers Consistently Praise

The 4.8-star rating across 240 reviews isn’t accidental. Buyers repeatedly mention the wire’s pliability — “much easier to work with than the solid 10 AWG I used last time,” one reviewer noted. Another commented on the clean stripping: “The insulation doesn’t stick to the copper like cheap brands. You can strip a foot of jacket in seconds without scoring the conductors.”

Several reviewers used this for EV charger installations, confirming the 30-amp capacity handles the continuous load requirement (derated to 24 amps for continuous use per NEC). The consistent copper quality also earned praise from DIYers who’d been burned by off-brand wire with brittle insulation that cracked during installation.

Where It Falls Short

The honest downsides: This cable is stiff in cold weather. If you’re working in an unheated garage in January, expect to warm the coil or fight the jacket. That’s true of all NM-B, but the thicker 10 AWG jacket makes it more pronounced than lighter gauges.

The price is the other sticking point. Southwire carries a premium over generic cable, and if your local big-box store sells the same spec for less, you’re paying for Amazon’s convenience and fast delivery. That’s worth it for a weekend project when you can’t make a supply run, but it’s a real consideration for cost-conscious buyers.

Who Should Buy This

This wire is for the serious DIYer or the professional who values reliability over saving a few bucks per foot. If you’re installing a 30-amp circuit for an EV charger, a mini-split, a subpanel feed, or upgrading an appliance circuit, this is the right tool. It’s also ideal if you’re running cable through conduit — the stranded conductors pull far more smoothly than solid.

Skip it if you’re wiring a basic 15-amp lighting circuit (you don’t need 10 AWG for that — 14/2 will do) or if you’re on a tight budget and already planning a trip to the hardware store anyway.

FAQ

Q: Can this wire be used in conduit? A: Yes, but with a caveat. The NM-B jacket is rated for dry locations and can be pulled through conduit, but it’s not rated for wet locations. For underground or exterior runs, you need UF-B cable instead.

Q: What’s the maximum amperage for this wire? A: The conductor is rated for 30 amps at 60°C termination, but for continuous loads (more than 3 hours), you must derate to 80% — so 24 amps. That means a 30-amp breaker feeding an EV charger is fine, but you can’t push 40 amps through it.

Q: Is stranded or solid wire better for this application? A: For 10 AWG and larger, stranded is generally preferred because it’s more flexible and easier to terminate. Solid 10 AWG is fine but significantly harder to work with in tight spaces.

The Verdict

Buy it if: You’re running a 30-amp circuit and want wire that pulls clean, strips easily, and won’t leave you short on length. The stranded copper construction is genuinely easier to work with than solid alternatives.

Skip it if: You’re on a strict budget and have easy access to a building supply store, or you only need a short run where the price premium isn’t justified.

Rating: 4.6/5 — Deducting a half-star for the cold-weather stiffness and the premium pricing. But for a critical circuit that needs to be right the first time, this wire earns its keep.

Where to Buy

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Last updated: 2026-08-06. Ratings and prices current as of review date. Verify on Amazon before purchasing.