Electrical Cable Sizing Calculator — NZ

Calculate the correct cable size for NZ electrical installations — current capacity, voltage drop, and circuit breaker sizing.

NZ Electrical Standards

All electrical installations in NZ must comply with AS/NZS 3000 (Wiring Rules) as adopted under the NZ Electricity Regulations 2010.

Common Cable Sizes

Application Typical cable
General power circuits 2.5mm² TPS
Lighting circuits 1.5mm² TPS
Hot water / stove 4mm² or 6mm²
Air conditioning (large) 6mm² or 10mm²
Sub-board / main feed 16mm²+

Voltage Drop Limits (AS/NZS 3000)

  • 5% maximum from supply point to any point in the installation
  • At 230V: maximum 11.5V drop allowed
  • Longer cable runs always need larger cable to compensate

Important

All electrical work in NZ must be carried out by a Registered Electrical Worker (REW). This calculator is a reference tool for planning purposes only. Find licensed electricians in your area.