What Is Bare Copper Wire? | Uninsulated Grounding Basics

Bare copper wire is an uninsulated copper conductor used primarily for grounding and bonding in electrical systems.

When an electrician asks for bare copper wire, they mean copper with no insulation, no jacket, and typically no protective coating of any kind. The metal itself does the work. That bare surface is exactly what makes it the standard choice for grounding and bonding, where the conductor needs direct contact with earth or with other metal parts. Whether you’re wiring a subpanel or bonding a water pipe, this is the wire that carries fault current safely to ground — and it earns the name “grounding wire” on every job site.

What Is Bare Copper Wire Made Of?

The construction depends on the job. Solid wire is stiff and holds its shape, which suits fixed runs. Stranded wire flexes and bends around corners, which suits conduit and tight spaces.

Manufacturers also offer different tempers, each with its own balance of strength and flexibility:

• Hard drawn — the stiffest, strongest temper, common for overhead spans.
• Medium hard drawn — a middle ground for general use.
• Soft (annealed) — the most flexible, easiest to bend and route.

Standard specs come from ASTM B3 for soft drawn and ASTM B8 for concentric stranded constructions. Most suppliers list sizes from 14 AWG solid up to 4/0 stranded, so nearly any residential or commercial grounding job has a match.

What Is Bare Copper Wire Used For?

Bare copper wire exists for grounding and bonding. In a residential panel, the bare ground wire connects the neutral bus to the ground rod outside. In commercial work, it bonds metal conduit, equipment housings, and structural steel so that any fault current has a safe path to earth. It is also used overhead where exposed conductor is acceptable and insulation is unnecessary.

What it is not for: circuits that carry live current where insulation is required by code. Bare copper has no jacket, so it cannot serve as a hot or neutral conductor inside walls. If the application demands insulated conductors, bare copper is the wrong material.

Bare Copper Wire Specifications

Manufacturers publish detailed spec tables because one “8 AWG” wire is not the same as another. Strand count, temper, and diameter all shift the numbers that matter.

Those resistance and breaking-strength figures come from published tables at Southwire’s bare copper specs. For any real installation, check the specific product’s own table, because values shift with AWG, strand class, and temper.

Bare vs. Tinned Copper Wire

Bare copper is frequently confused with tinned copper, and the distinction matters. Tinned copper has a thin layer of solder-like coating over the copper. That coating resists corrosion in marine and high-humidity environments. Bare copper has no coating at all.

The trade-off is simple. Bare copper costs less and conducts slightly better, but it oxidizes when exposed to air and water, turning green or black over time. Tinned copper costs more and resists that corrosion, which is why it dominates boat wiring. For standard residential grounding, bare copper is the conventional choice and oxidization is rarely a problem because the conductor sits inside a panel or buried in earth. If you need a wire that sits exposed to the elements for years, tinned is the better pick.

One more common mistake: assuming any bare copper is fine for any grounding job. A 14 AWG solid wire handles a small bond. A 2/0 stranded conductor grounds an entire service. Match the AWG to the circuit size and local code, not to whatever spool is closest. For a practical comparison of top-rated spools and sizes, see our roundup of the best bare copper wire options.