Most NZ homes built before 1980 still have their original wiring. That's 40+ years of electrical infrastructure carrying modern loads it was never designed for. Electrical faults cause around 10% of NZ house fires — and many of them start in walls that look perfectly fine from the outside.
Here are the signs that your wiring is telling you something is wrong, what each sign means, and what to do about it.
1. Circuit Breakers Trip Frequently
The occasional trip is normal — it's the circuit breaker doing its job. But if the same breaker trips repeatedly, or multiple breakers trip when you run normal household loads (the oven and the kettle at the same time), that points to a problem.
What it means: Circuits are either undersized for their load, or there's a fault drawing excess current. Older NZ homes often have only one or two circuits for the whole house — every appliance competing for the same wire.
What to do: Note which breaker trips and under what load. Call an EWRB-licensed electrician to assess. Don't just swap the breaker for a higher-rated one — that defeats the protection.
2. Lights Flicker or Dim When Appliances Run
You switch on the microwave and the lights dip. The heat pump kicks in and the lights flicker momentarily. This is called a "voltage drop" and it's a classic sign of undersized wiring or loose connections.
What it means: The wiring gauge is too small for the current being drawn, or a connection has corroded or loosened. Either causes resistance, which drops voltage. In older NZ homes, this often means the wiring was sized for 1960s appliance loads — not heat pumps, EV chargers, and induction cooktops.
What to do: Have an electrician check the load on your main circuits and assess whether wiring gauge is adequate. This is often the first step before adding a heat pump or EV charger circuit.
3. Warm or Discoloured Outlets and Switches
Switch plates or power points that feel warm to the touch, or that have yellowing or scorch marks around them, are a serious warning. Warmth means electrical resistance; scorch marks mean it's already been running hot.
What it means: Loose connections, overloaded circuits, or wiring rated below the load being drawn. This is a fire risk.
What to do: Stop using that outlet immediately. Call an electrician — this is urgent, not a "book it next week" situation.
4. Burning or Plastic Smell Near Outlets or the Switchboard
A burning smell that you can't trace to an obvious source — food, a forgotten appliance — but that seems to come from the walls, ceiling, or from around the switchboard, is a serious warning sign.
What it means: Wiring insulation is overheating somewhere inside the wall. The NZ wiring standard of the 1950s–70s often used rubber-insulated wire. Rubber degrades over decades and can crack, exposing live conductors to combustible materials.
What to do: This warrants turning off the relevant circuits and calling an electrician immediately. If the smell is strong or you can see discolouration around outlets, call the fire service first.
5. Old Fuse Board (Rewirable Fuses)
New Zealand homes switched from rewirable fuse boards (with actual fuse wire) to modern MCB (miniature circuit breaker) boards over several decades. If your home still has a fuse board with porcelain or Bakelite fuse holders, that's a sign the rest of the wiring is also from that era.
What it means: Beyond age, rewirable fuses are a safety issue because homeowners often replace blown fuse wire with the wrong size (or with anything conductive, like aluminium foil). A larger fuse wire allows more current to flow before blowing — removing the protection.
What to do: Switchboard upgrades to modern MCBs are one of the most common electrical upgrades in NZ older homes. Cost: $2,000–$5,000 depending on the number of circuits and whether additional circuits are added.
6. Outlets Without Earth (Two-Pin Outlets)
Older NZ homes sometimes have two-pin outlets — live and neutral only, with no earth. Modern standards require earthed outlets (three-pin). Earthing is the safety mechanism that routes fault current safely to ground rather than through a person.
What it means: Unearthed circuits don't provide the same shock protection as modern wiring. Many older appliances required it — modern appliances and safety standards assume it.
What to do: An electrician can earth existing circuits in many cases, or add new circuits. RCD (Residual Current Device) protection can provide some additional safety on unearthed circuits as an intermediate measure.
7. Aluminium Wiring
NZ homes built in the late 1960s to early 1980s sometimes used aluminium wiring as a substitute for copper (copper was expensive at the time). Aluminium is a legitimate conductor, but it has a different expansion rate than copper and the connectors of the era weren't designed for it.
What it means: Aluminium/copper connections can loosen over time as the metals expand and contract at different rates, creating resistance and heat. This is a known fire risk that has caused fatalities in NZ.
What to do: If you're not sure whether your home has aluminium wiring, have an electrician check. The wire is silver-coloured rather than copper-coloured. Solutions range from special connectors ("AlumiConn" or similar) to full rewiring. Get professional advice — this is a safety-critical assessment.
8. No RCD Protection
Residual Current Devices (RCDs, also called ELCBs or "safety switches" in common parlance) detect earth leakage current and trip the circuit within milliseconds — fast enough to prevent electrocution. Modern NZ wiring standards require RCDs on socket circuits and certain other circuits.
What it means: Without RCD protection, a person who becomes part of a fault circuit (e.g., touches a live conductor while grounded) relies on the MCB to trip — which typically trips at 10–30 amps, well above the 30mA that can cause cardiac arrest.
What to do: Have your switchboard assessed. Adding RCD protection to existing circuits is relatively inexpensive ($300–$600 per RCD) and significantly improves safety. Many insurers and landlords now require it.
9. Extension Cords Used Permanently
If there are extension cords or power boards running permanently to make up for insufficient power points, that's both a usage symptom and a hazard indicator.
What it means: The home's original wiring had too few circuits for modern needs. More immediately: permanent extension cords are a tripping hazard and, if overloaded, a fire hazard.
What to do: Have an electrician add circuits and outlets where you need them. Under NZ law, adding outlets involves wiring and is restricted electrical work — it must be done by an EWRB-licensed electrician. New outlet: $200–$450 per outlet depending on location.
10. The House Is More Than 40 Years Old and Has Never Been Rewired
If your home was built before 1985 and the electrical system has never been upgraded, the wiring is likely at or past the end of its practical life. NZ regulations don't mandate rewiring at a set age, but rubber-insulated wiring from the 1960s and 1970s has a practical lifespan of 40–50 years — it becomes brittle, cracks, and loses insulation integrity.
What it means: Even without obvious symptoms, the wiring may be degrading inside walls. An electrical inspection will assess the actual condition.
What to do: Book an electrical inspection from an EWRB-licensed electrician. This typically costs $200–$400 and covers the visible components, the switchboard, and a general assessment of circuit condition. A full thermal imaging inspection ($400–$800) can detect hot spots inside walls.
What Does Rewiring Cost in NZ?
Full house rewiring is a major project — it involves running new cable through existing walls, which usually means either opening walls or using surface conduit.
| Project | Typical cost |
|---|---|
| Switchboard upgrade (fuses to MCBs) | $2,000–$5,000 |
| Add RCD protection to existing board | $600–$1,500 |
| Rewire single room | $2,000–$5,000 |
| Partial rewire (high-use areas) | $5,000–$15,000 |
| Full house rewire (3-bed house) | $15,000–$40,000 |
| Full rewire + switchboard + additional circuits | $20,000–$60,000 |
Costs vary significantly by how accessible the wiring is, whether ceilings have to be opened, and the city. Auckland is consistently at the higher end.
Getting Quotes
Electrical quotes vary more than most homeowners expect. Get at least 3 quotes from EWRB-licensed electricians, and ensure the scope is the same across all quotes (ask them to specify: what circuits are being rewired, what the new switchboard specification is, whether earthing is included, and what certificates will be provided).
After any work, the electrician must provide a Certificate of Compliance — keep it with your property records.
Find licensed electricians near you: Find Electricians on NZ Tradie Tools
Is It Always Rewiring?
Not every symptom requires full rewiring. Sometimes the fix is targeted: - Tripping breaker → often a faulty appliance, not bad wiring - Flickering lights → sometimes just a loose bulb or a failing fitting - Warm outlet → sometimes a loose connection behind the plate
An electrician's inspection will distinguish between isolated faults and systemic wiring degradation. Start with an inspection before committing to a full rewire.
Related: What Electrical Work Can I Do Myself in NZ? | Electrician Cost Per Hour NZ | How to Hire an Electrician NZ