What is aluminum wiring?
Updated August 2026
Aluminum wiring is solid aluminum branch-circuit wire, used instead of copper in an estimated two million US homes built between 1965 and 1975. A copper shortage in those years made aluminum the cheap conductor for the 15-amp and 20-amp circuits feeding outlets, switches, and light fixtures. The metal carries current perfectly well. The trouble sits at the ends of it, where aluminum behaves under a screw terminal in ways copper never does.
Where it is
The build date is the first filter: a house finished between 1965 and 1975 deserves a look. Next, go where cable is exposed, an unfinished basement ceiling or the attic, and read the printing on the jacket. Aluminum cable is stamped AL, ALUM, or ALUMINUM every foot or two, and the conductor under the insulation is silver-gray instead of penny-colored. Two more tells show up without opening anything: receptacles and switches marked CO/ALR, and cover plates that feel warm after an appliance has run for an hour.
What it does
Aluminum moves the same current copper does, just at a fatter gauge: a 15-amp circuit needs 12 AWG aluminum where copper gets by with 14 AWG. Every known problem happens at the terminations. The metal expands and contracts more than copper with each heating cycle, it creeps out from under a screw across years of that, and its surface oxide conducts poorly, so the joint gains resistance and resistance makes heat. One loose terminal can char a receptacle, scorch the box, and reach the framing behind it. The Consumer Product Safety Commission found that homes with pre-1972 aluminum branch circuits are 55 times more likely to have a connection reach fire-hazard conditions than copper-wired homes.
Maintenance
Nothing gets changed or lubricated here, so treat aluminum wiring as an inspection item: a licensed electrician opens and checks terminations every 1–2 years, and you do a hands-on pass each season between visits. Touch cover plates and dimmers for warmth, watch for outlets browning around the slots, and listen for a faint sizzle in a quiet room. Any of the three means kill that circuit at the panel and call someone. Fold the electrician visit into your panel inspection, and track which devices have been corrected on the electrical panel checklist, because remediation stalls at outlet 12 of 60 when nobody is counting.
What it costs to replace
A replacement aluminum wiring runs $50–150 per device connection to pigtail with COPALUM crimps or AlumiConn connectors, and $8,000–15,000 to rewire an average house in copper.
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Frequently asked questions
Is a house with aluminum wiring safe to live in?
Yes, once the connections are corrected, and the correction is the connections rather than the wire inside the walls. The two repairs the Consumer Product Safety Commission accepts are COPALUM crimp sleeves, applied with a licensed tool by a certified electrician, and AlumiConn set-screw connectors that pigtail a short copper tail onto each aluminum conductor. Budget $50–150 per device. Standard wire nuts, including the purple twist-ons sold for aluminum-to-copper splices, are not accepted repairs. Devices stamped CO/ALR are rated to take aluminum directly at outlets and switches.
Will homeowners insurance cover aluminum wiring?
Carriers split three ways: some decline the house, some write it with a surcharge, and some issue a normal policy once a licensed electrician certifies that every device has been pigtailed or fitted with CO/ALR hardware. Expect the question on any new application and expect an underwriter to revisit it after a claim. Keep the electrician letter with your closing documents, since the next buyer and the next carrier both ask for it. Quotes differ enough between companies that calling three is worth an hour.
How much does it cost to fix aluminum wiring in a whole house?
Count devices before you take bids. A 1,500-square-foot house typically holds 40–80 outlets, switches, and fixtures, and at $50–150 per connection a full pigtail job lands around $3,000–9,000, often split across two or three visits. A complete copper rewire runs $8,000–15,000 in an average home and climbs in plaster walls or a two-story with no attic above the second floor. Pigtailing costs less and satisfies most insurers, which is why it is the common choice.
How do I tell aluminum wiring from copper?
Shut the power to one receptacle at the panel, pull the device out of the box, and look at the conductor: aluminum is silver-gray, copper is the color of a penny. Without touching a wire at all, read the cable jacket in the basement or attic for AL or ALUMINUM markings. One caveat matters. The thick multi-strand aluminum feeding the meter and panel, and aluminum feeders to a range or subpanel, are ordinary and not the hazard. Single-strand aluminum on 15-amp and 20-amp circuits is.