Skip to main content
ECalPro
Try Free

Cable Sizing Calculator per AS/NZS 3008.1.1:2017 for Residential Installations

AS/NZS 3008.1.1:20172017Residential Installations

Cable sizing for AS/NZS 3008 residential installations uses Table 3 current-carrying capacities for V-75 (PVC 75 °C) or X-90 (XLPE 90 °C) cables, applies Table 13 derating for grouped cables in residential switchboards, and verifies voltage drop per Table 25 stays within the AS/NZS 3000:2018 limit of 5% from the point of supply to the final sub-circuit outlet.

Calculate Cable Sizing Calculator Now

Quick Reference Table

AS/NZS 3008 Residential Cable Sizing References — AS/NZS 3008.1.1:2017 (2017)
ParameterValue / RequirementClause Reference
Current-carrying capacitySingle & multicore cable ratings by installation methodTable 3, Columns 3-21
Grouping deratingFactors for cables bunched in enclosuresTable 13
Ambient temperature deratingCorrection for air temperatures above 40 °CTable 14
Voltage drop constantsmV/A/m values for AC and DC circuitsTable 25
Maximum demandDomestic load assessmentAS/NZS 3000:2018, Table C1

How to Calculate Cable Sizing for Residential Installations

  1. 1

    Determine the circuit design current

    Calculate the maximum demand for the domestic circuit. Typical Australian sub-circuits: lighting (10 A), socket outlets (20 A), cooktop (32 A), air conditioning (per unit nameplate).

  2. 2

    Select the installation method

    Identify the wiring method — typically enclosed in wall (Column 6/7 of Table 3) or clipped to surface in roof space (Column 3/4). Australian ceiling spaces can exceed 50 °C.

  3. 3

    Apply derating factors

    Derate for grouping (Table 13) in the switchboard and for ambient temperature (Table 14) — critical in Australian climates where roof-space temperatures regularly reach 50-60 °C.

  4. 4

    Select cable size from Table 3

    Choose the minimum cable size where the derated current rating exceeds the design current. Common residential sizes: 1.5 mm² (lighting), 2.5 mm² (socket outlets), 4-6 mm² (cooking/AC).

  5. 5

    Check voltage drop per Table 25

    Calculate voltage drop using mV/A/m values from Table 25. AS/NZS 3000:2018 limits total drop to 5% from the point of supply, with a sub-circuit allowance of 3%.

Try the Cable Sizing Calculator

Run compliant AS/NZS 3008.1.1:2017 calculations for residential installations — free, instant results with full clause references.

Calculate Cable Sizing Now

BS 7671 vs AS/NZS 3008 Cable Sizing Comparison

ParameterBS 7671AS/NZS 3008
RegionUnited KingdomAustralia & New Zealand
Voltage drop limit3% lighting / 5% other5% general (AS/NZS 3000 Table C7)
Reference ambient temp30°C air40°C air (Table 22)
Ampacity tablesAppendix 4 Tables 4D1A–4J4ATables 13–20 (by method)
Derating tablesCa, Cg, Ci, Cc factorsTables 22, 24, 25, 26 factors
Soil temp reference20°C25°C (Table 25)
Compare with ECalPro

Frequently Asked Questions

Table 3 base ratings assume 40 °C ambient for cables in air (compared to 30 °C in BS 7671). This is why AS/NZS ratings appear lower than BS 7671 — the Australian base temperature is already higher. For temperatures above 40 °C, apply Table 14 correction factors.
A 2.5 mm² V-75 (PVC 75 °C) cable installed enclosed in wall (Table 3, Column 7) has a base rating of 23 A. After applying grouping derating from Table 13 for cables in the switchboard, this typically remains adequate for a 20 A circuit with moderate grouping.
AS/NZS 3000:2018 allows a total voltage drop of 5% from the point of supply to the final outlet, with a recommended sub-circuit limit of 3%. BS 7671 uses the same 5% overall but splits it as 3% for lighting. The voltage drop constants in AS/NZS 3008 Table 25 are structured differently from BS 7671 Appendix 4 tables.

Related Guides

Cable Sizing — AS/NZS 3008.1.1:2017

Commercial Buildings

Cable Sizing — BS 7671

Residential Installations

Cable Sizing — NEC (NFPA 70)

Residential Installations