Installing or replacing an oven or hob is one of the most common kitchen upgrades NZ homeowners tackle — but getting the electrical side right is absolutely critical. The wrong cable size can cause overheating, tripped breakers, or even a house fire. Here's what you need to understand before any work begins.
Why Cable Sizing Matters
Ovens and hobs are among the highest-draw appliances in your home, often pulling anywhere from around 2,400 watts for a small hob element up to 10,000 watts or more for a large freestanding range cooker. Cable sizing determines how much current a cable can safely carry without overheating. Undersized cable is a serious fire hazard and a breach of the NZ Electrical Code of Practice.
In New Zealand, all fixed electrical wiring must comply with the Electricity (Safety) Regulations 2010 and the relevant wiring standards. WorkSafe NZ oversees electrical safety, and all electrical installation work on fixed wiring is restricted work — meaning it must be carried out by a registered electrician.
Typical Cable Sizes Used for Ovens and Hobs
The cable size required depends on the appliance's rated load (in watts or amps), the length of the cable run, and how the cable is installed (e.g. clipped to surface, in conduit, or buried in insulation). As a general guide:
| Appliance Type | Typical Load | Common Cable Size (NZ) |
|---|---|---|
| Single hob or small oven | Up to ~20A | 2.5mm² TPS (twin & earth) |
| Large oven or hob | 20A–32A | 4mm² TPS |
| Large range cooker / double oven | 32A–45A | 6mm² or 10mm² TPS |
TPS (thermoplastic-sheathed) flat cable is the standard type used in NZ domestic wiring. The figures above are indicative only — your electrician will calculate the correct size based on your specific appliance rating, cable run length, and installation method.
Important: These are general guides, not a substitute for a licensed electrician's assessment. Always check your appliance's data plate for its rated current draw.
Dedicated Circuit and Correct Breaker
Ovens and hobs should always be on a dedicated circuit — that is, their own circuit breaker in your switchboard, not shared with other appliances. The circuit breaker rating must be matched to the cable size and the appliance load. Using an oversized breaker with undersized cable defeats the protection the breaker is meant to provide.
For most freestanding cookers and large hobs, a 32A or 40A circuit with appropriately sized cable and a dedicated isolator switch (located within sight of the appliance) is standard practice in NZ kitchens.
What a Homeowner Can and Cannot Do
This is where it's important to be clear about NZ law:
What you CAN do yourself
- Plug in a freestanding oven or hob that uses a standard 10A or 15A plug and socket (if one is already installed).
- Read your appliance manual and note the rated wattage and amperage before calling an electrician.
- Plan your kitchen layout and discuss your needs with a qualified tradesperson.
What is RESTRICTED work (must be done by a licensed electrician)
- Installing or modifying any fixed wiring — including running a new circuit from the switchboard.
- Installing or replacing a hardwired connection (most ovens above 10A are hardwired).
- Installing or relocating a dedicated isolator switch.
- Any work inside your switchboard, including fitting a new circuit breaker.
The Electrical Workers Registration Board (EWRB) maintains the register of licensed electricians in NZ. Unlicensed electrical work is illegal, can void your home insurance, and puts lives at risk.
Induction Hobs vs Traditional Electric Hobs
Induction hobs have become very popular in NZ kitchens. While they are generally more energy-efficient, a full-size induction hob can still draw a significant load — often 7,000W or more — so cable sizing requirements are similar to traditional ceramic or radiant hobs. Don't assume an induction hob needs less wiring capacity without checking the data plate.
Older Homes and Existing Wiring
If your home was built before the 1990s, it may have older wiring that isn't rated for modern high-draw appliances. BRANZ research highlights that older NZ homes can have wiring that doesn't meet current standards. A licensed electrician can assess whether your existing circuit is safe and up to code before connecting a new appliance.
When to Call a Professional
You should always engage a registered electrician for any oven or hob installation involving fixed wiring. This includes:
- Installing a new circuit from the switchboard to the kitchen.
- Hardwiring an oven or connecting it to an isolator outlet.
- Upgrading an existing circuit to handle a higher-rated appliance.
- Any work where you're unsure whether the existing wiring is adequate.
A licensed electrician will size the cable correctly, install the right breaker, issue a Certificate of Compliance (CoC), and ensure the work meets the NZ Electrical Code of Practice. You can find qualified local electricians on tradedirectory.co.nz.