Electrical · Materials

Electrical materials

Most residential branch circuits use copper conductors in nonmetallic sheathed cable (commonly called Romex). Aluminum is standard for large service-entrance and feeder conductors, where it is engineered for the job, but aluminum branch-circuit wiring installed in many homes built roughly 1965–1972 is a known concern that usually needs remediation rather than being left alone.

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Materials are where quotes quietly differ. Wire gauge is dictated by the circuit's ampacity and the run length, not by preference, so a contractor undercutting on wire size is not saving you money — they are creating a hazard an inspector should catch.

The copper-versus-aluminum question splits by application. On the service and feeder side, aluminum is normal, cheaper, and used with the correct connectors and anti-oxidant treatment. On branch circuits, older solid aluminum wiring behaves differently from copper at connections, which is why remediation focuses on the terminations. HomeGuide's 2026 data notes copper pigtailing at connection points runs about $50–$75 per outlet, which is dramatically cheaper than a whole-house rewire at $12,000–$36,600. If someone quotes only the rewire without mentioning remediation as an option, ask why.

Conduit versus cable is largely driven by location and local rules — some jurisdictions require conduit where others permit NM cable, and exterior, garage, and unfinished-basement runs have their own requirements. This is another place where the adopted local code, not a general rule, decides.

One thing you can check without any trade knowledge: everything installed should be listed by a recognized testing laboratory. Ask that the quote specify listed materials and that any unusual product be named.

How to choose

Ask for aluminum remediation as an option, not just rewiring: If aluminum branch wiring is found, a connection-level remediation is often available at roughly $50–$75 per outlet versus a five-figure rewire. Get both priced.
Wire gauge is not negotiable: It follows the breaker size and run length. If a contractor offers a cheaper price by using smaller wire on the same breaker, walk away.
Confirm materials are listed: Ask the quote to state that all devices, breakers and cable are listed by a recognized testing lab. Unlisted imported breakers are a real problem in online marketplaces.
Local rules decide conduit vs. cable: Do not assume what your neighbor's house has is what yours can have. Your building department's amendments govern.
Ask what happens to the walls: Rewiring in finished walls means drywall or plaster repair, which HomeGuide puts at $1,000–$5,000. Confirm whether it is in the quote or your problem.

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FAQ

Electrical materials — common questions

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Is aluminum wiring dangerous?

The concern with older solid aluminum branch-circuit wiring is at the connections, where expansion, oxidation and loosening can cause overheating. It is generally addressed through approved remediation at the terminations rather than automatic full replacement. Have a licensed electrician inspect the actual connections before deciding — and tell your insurer, because some carriers ask about it.

What is Romex?

A common brand name for nonmetallic sheathed cable (type NM), the standard flexible cable used for interior residential branch circuits in most of the US. Whether it is permitted in a given location depends on your jurisdiction's adopted code and local amendments.

Does copper wiring cost much more than aluminum?

For branch circuits, copper is the norm and the material cost is a small fraction of a job dominated by labor. For large service and feeder runs, aluminum is standard and materially cheaper, which is why you will see it there even in new construction.

Can I supply my own materials to save money?

Most reputable electricians will decline, and reasonably so — they warrant the installation and cannot warrant parts they did not source, and counterfeit breakers are a documented problem in online resale. The savings are usually small relative to the risk.

Sources

Where these figures come from

HomeGuide — Cost to Replace Knob and Tube Wiring (2026) · retrieved 2026-07-25