How long does electrical wiring last
Modern copper wiring lasts 50 to 70 years and often longer. What ages out first is the panel, the devices, and the fact that a house wired in 1968 has a fraction of the circuits a household now needs.
National average
$15,000
per project
On this page
- What lasts how long
- What actually ages
- The findings that mean money
- The signs worth acting on
- Rewire, or not
- Frequently asked questions
- How do I know what wiring I have?
- Does a home inspection cover this?
- Will my insurer ask?
- How many circuits should a house have?
- Is old wiring safe if nothing has gone wrong?
Modern copper wiring with thermoplastic insulation lasts 50 to 70 years and often longer. What ages out of a house first is not the wire; it is the panel, the devices and the fact that a house wired in 1968 has a fraction of the circuits a household now needs.
That distinction is why "the wiring is 55 years old" is not by itself a reason to rewire, and why "there are two outlets in this bedroom" often is.
What lasts how long
| Component | Typical life |
|---|---|
| Copper wiring, modern NM cable | 50 to 70 years or more |
| Rubber-insulated cable, pre-1960 | 40 to 60 years, insulation fails first |
| Knob and tube | Installed 1880s to 1940s, past life |
| Aluminium branch wiring | Connections fail regardless of age |
| Breaker panel | 25 to 40 years |
| Circuit breakers | 30 to 40 years |
| Fuse box | Obsolete rather than worn |
| Outlets and switches | 15 to 30 years |
| GFCI devices | 10 to 15 years |
| AFCI breakers | 15 to 25 years |
| Smoke alarms | 10 years, then replace |
| Carbon monoxide alarms | 5 to 7 years |
| Surge protector at the panel | 5 to 15 years |
| Light fixtures | 20 to 40 years |
| LED lamps | 15,000 to 50,000 hours |
| Service entrance cable | 40 to 60 years |
| Underground service lateral | 30 to 60 years |
What actually ages
Insulation, not conductor. Copper does not wear out. The insulation around it becomes brittle, particularly the rubber and cloth used before about 1960, and it cracks where the cable has been flexed, heated or disturbed. This is why old wiring in an undisturbed wall is often fine and the same wiring at a light fixture is not.
Connections. Every screw terminal, wire nut and backstabbed device is a point that can loosen. Heat and time do the loosening, and a loose connection makes heat, which is the cycle behind most electrical fires. This is what thermal imaging looks for.
Devices. Outlets wear mechanically. A plug that falls out is a worn contact, which is a heat source, and it is a $3 part.
Capacity, which is not ageing at all. A 1955 house has 60 or 100 amp service and maybe eight circuits. Nothing about it has degraded; the household simply has forty years more equipment than the house was designed for.
The findings that mean money
Six specific things, roughly in order of what they cost:
Federal Pacific Stab-Lok or Zinsco panels. Breakers that may not trip on overload. $1,500 to $4,000 to replace and widely recommended.
Aluminium branch wiring, roughly 1965 to 1973. $2,000 to $8,000 to pigtail every device.
Knob and tube. $8,000 to $30,000 to rewire, and the most common reason an insurer declines a policy.
Ungrounded three-prong outlets, where somebody fitted a modern outlet with no ground behind it. $150 to $400 a location to make right, and the most misleading of the six.
A fuse box still in service. Not inherently unsafe, and obsolete, and often undersized. $1,500 to $4,000 for a panel and $1,500 to $6,000 if the service needs upgrading too.
Cloth-covered rubber cable with visible cracking. Circuit-by-circuit replacement at $800 to $2,500 each, or a rewire.
The signs worth acting on
- Breakers that trip regularly on one circuit
- A warm outlet, switch plate or cable
- Any burning smell, which is now rather than later
- Lights dimming or brightening as appliances start
- A plug that falls out of an outlet
- Scorch marks or discolouration on a device
- Extension leads as permanent wiring, which is a capacity problem announcing itself
- A panel with double-tapped breakers, where two circuits share one breaker
The first three are calls. The rest are a conversation with an electrician at the next convenient time.
Rewire, or not
Rewire when the house has knob and tube, when the insulation is visibly failing, when the circuit count cannot support how the house is used, or when the walls are open for a major renovation anyway.
Do not rewire because of age alone. Fifty-year-old copper in sound condition, with a modern panel, GFCI and AFCI protection where required and enough circuits, is a perfectly good electrical system.
Phase it where possible. Rewiring the kitchen during a kitchen remodel and the bathrooms during a bathroom remodel gets most of a house done at a fraction of the disruption, because the walls are open regardless.
Frequently asked questions
How do I know what wiring I have?
Look at the cable where it enters the panel. Modern NM cable is a flat plastic sheath, usually white, yellow or orange by gauge. Older cloth-covered cable looks like fabric. Knob and tube runs as separate conductors through ceramic supports. Aluminium is stamped AL on the sheath.
Does a home inspection cover this?
Superficially. For a house built before about 1980, a dedicated electrical inspection at $200 to $600 is worth it, and it is the single best money spent before buying an older house.
Will my insurer ask?
Increasingly yes, on houses over about 30 years old. Knob and tube, aluminium branch wiring and Federal Pacific panels are the three specific things they ask about.
How many circuits should a house have?
A modern three-bedroom house typically has 20 to 30. Kitchens alone need several dedicated circuits under current code. If yours has eight, that is the number worth acting on rather than the age of the wire.
Is old wiring safe if nothing has gone wrong?
Often, and undisturbed old wiring genuinely does last. The risks come from age-hardened insulation, decades of amateur modification, and modern loads on circuits designed for a lamp and a radio. An inspection tells you which of those apply to your house.
Read next
Electrical inspection cost$200 to $600per eachAn electrical inspection costs $200 to $600, typically $350. It is the cheapest way to find out whether the wiring in a house is a maintenance item or a five-figure project.
Aluminum wiring repair cost$2,000 to $8,000per projectRemediating aluminium branch wiring costs $2,000 to $8,000, typically $4,000. It was installed in roughly two million American homes between 1965 and 1973, and it is not a defect you can ignore.
Knob and tube wiring replacement cost$8,000 to $30,000per projectReplacing knob and tube costs $8,000 to $30,000, typically $15,000. Where it survives it is at least eighty years old, has no ground, and is the most common reason an insurer declines to cover a house.
Ungrounded outlet fix cost$150 to $600per eachFixing an ungrounded outlet costs $150 to $600 per location. A three-prong outlet with no ground behind it is far more dangerous than a two-prong one, because it looks safe.
House rewiring cost$600 to $1,700per sq ftRewiring costs $6 to $17 per square foot, so $9,000 to $25,500 for a 1,500 square foot house. Those figures usually exclude the wall repair, which can be a third of the project.