Aluminum Wiring in Ontario
Ontario homes built between the mid-1960s and late 1970s may have aluminum wiring. The Electrical Safety Authority (ESA) says aluminum wiring is permitted by the Ontario Electrical Safety Code and is safe when proper connections and terminations are made, but the original connections in older homes can fail. Many insurers want it inspected, and ESA recommends having a Licensed Electrical Contractor assess it.
Which homes have aluminum wiring?
ESA states that if your home was built between the mid-1960s and late 1970s, you may have aluminum wiring. ESA also notes that some homes have a mixture of aluminum and copper wiring, so a partial renovation does not mean the whole house has been changed.
Aluminum is still used today. ESA points out that it is widely used for larger commercial and industrial feeders and by electrical distribution companies, including the supply service cable to most homes.
Is aluminum wiring safe?
ESA lists two common myths: that aluminum wiring was recalled because it is a fire hazard, and that it is no longer used for interior wiring. Neither is true. The Ontario Electrical Safety Code permits it.
The issue is the connections. ESA says reported problems have been related to the overheating and failure of aluminum wiring terminations, due to aluminum's tendency to oxidize and its incompatibility with devices designed for copper wiring. ESA's position is that aluminum wiring is safe if proper connections and terminations are made without damaging the wire, using devices approved for aluminum.
Warning signs ESA lists
According to ESA, these may be evidence of failing aluminum terminations. If you notice any of them, stop using the outlet or switch and have it checked by a Licensed Electrical Contractor.
- —Warm cover plates
- —Discoloured switches or receptacles
- —Signs of arcing within switches or receptacles
- —Flickering lights
- —The smell of hot plastic insulation
Do not wait for warning signs
ESA warns that aluminum-wired connections have been known to fail and overheat without any prior indications. Where the original devices are not marked as suitable for aluminum, ESA strongly recommends replacing them with aluminum-rated, properly marked devices, or having copper tails installed.
ESA also notes that if original devices were replaced in the past with newer copper-only devices, those need to be replaced with devices rated for copper and aluminum.
How to tell if a device is rated for aluminum
ESA's 2025 flash notice lists the markings required on devices used with aluminum wiring.
- —Receptacles rated 20 amps or less: CO/ALR or AL-CU
- —Receptacles rated over 20 amps: AL-CU or CU-AL
- —Switches rated 20 amps or less: CO/ALR
- —Wire connectors joining aluminum and copper: AL-CU or CU-AL
How aluminum wiring is assessed and repaired
ESA says each home is different and must be assessed on its own. It recommends hiring a Licensed Electrical Contractor who knows the special techniques for working with and repairing aluminum wiring. The contractor should do an assessment, make the necessary repairs and have the work inspected by ESA.
Because problems are usually found at termination points, ESA describes the assessment as opening all outlets, including receptacles, switches, fixtures, appliance connections and the panel, and visually inspecting the terminations for signs of overheating. Where damage is found, the damaged conductor is cut back and repaired. This is not DIY work: ESA's notice covers specific requirements for terminations, connectors, box sizes and oxide inhibitors.
Insurance and aluminum wiring
Insurance is often what starts the conversation. ESA says some insurers will not provide or renew coverage on homes without an ESA inspection, and you may need to repair or replace the wiring and give your insurer a copy of the ESA Certificate of Acceptance. In some cases an insurer may require replacement with copper wiring. Ask your insurance company exactly what it requires before you plan the work.
Getting older wiring looked at
Troubleshooting and repairs are part of our residential electrical services and electrical service and repairs. If your home has aluminum wiring, mention it in your quote request so the visit can be planned around it. For added capacity, see panel and service upgrades. If your home is older still, our knob-and-tube wiring guide covers that wiring method.
We serve Guelph, Waterloo, Burlington and the other communities on our service areas page.
Sources and further reading
This guide summarizes information published by the Electrical Safety Authority, including Flash 25-18-FL (May 2025). It is general information, not advice about your specific property.
Questions about the wiring in your home?
Tell us the age of the home and what your insurer has asked for, and we will follow up on the next steps.