Electrical
House Wiring Cable Sizes: Which Cable for Lights, Sockets, Cooker and Geyser?
Short answer
As a typical rule of thumb for domestic wiring, lighting circuits use 1.5 mm² cable, socket circuits 2.5 mm², and heavy loads such as cookers and showers use 4 to 6 mm² with matching breakers. The correct size also depends on cable length, how the cable is installed and the standard being followed, so a qualified electrician should confirm each circuit.
Typical starting points
| Circuit | Common cable | Typical breaker |
|---|---|---|
| Lighting | 1.5 mm² | 6 to 10 A |
| Sockets | 2.5 mm² | 16 to 20 A |
| Water heater or geyser | 2.5 to 4 mm² | 16 to 25 A |
| Cooker or shower | 4 to 6 mm² or more | 32 to 40 A |
| Air conditioner | 2.5 to 4 mm² | Per manufacturer |
Indicative only. Correct sizing depends on load, length, installation method and the applicable standard.
Why cable size matters
- Too thin: overheats and can start a fire.
- Long runs cause voltage drop, so lights dim and motors struggle.
- The breaker protects the cable, so the breaker rating must not exceed the cable capacity.
Quality tips
- Use solid copper cable from a reputable manufacturer with proper markings.
- Avoid cable that looks thinner than labelled.
- Use conduit or trunking and proper junction boxes.
- Ensure earthing conductors are in place.
Next
See earthing and RCDs, breaker types and our wiring service.
Common questions
Can I use 2.5 mm² for everything?
No. Lighting can use thinner cable, and cookers and showers need thicker cable.
Does cable length matter?
Yes. Longer runs may need a larger cable to keep voltage drop acceptable.
Is cheap cable okay?
Poor cable may have undersized copper or weak insulation. Buy quality cable from reputable suppliers.