AS/NZS 3008.1.1:2025 — What Changed from the 2017 Edition and Why It Matters

The AS/NZS 3008.1.1:2025 edition replaces the 2017 edition that has governed cable selection in Australia and New Zealand for eight years. The revision was driven by three converging forces:

• Solar PV and battery storage growth: The 2017 edition was drafted before utility-scale solar farms and large commercial battery installations became routine. DC cable ratings above 1000 V were inadequately covered.
• Research on mutual heating: Field studies and finite-element thermal modelling conducted since 2017 revealed that the grouping factors in Table 25 were non-conservative for certain enclosed-tray configurations, particularly when cables are tightly packed in three or more layers.
• IEC harmonisation: Standards Australia committed to closer alignment with IEC 60364-5-52:2009+A2:2024, reducing discrepancies that create confusion for engineers working across jurisdictions.

The 2025 edition was published in November 2024, with a transition period allowing use of either edition until the next revision of AS/NZS 3000 (Wiring Rules) formally mandates the 2025 tables. In practice, most regulators expect the 2025 edition to become mandatory by mid-2026.

The most significant scope expansion in the 2025 edition is the inclusion of cable current ratings for DC circuits operating up to 1500 V. The 2017 edition covered AC cables up to 0.6/1 kV and had limited provisions for DC applications.

The new provisions address:

• String cable ratings for utility-scale solar: Solar farms increasingly use 1500 V DC string voltages (replacing the older 1000 V standard) to reduce balance-of-system costs. The 2025 edition provides current rating tables for single-core DC cables in above-ground and buried configurations up to 1500 V DC.
• Battery energy storage systems (BESS): DC cables connecting battery racks to inverters in commercial and utility-scale BESS installations now have explicit rating tables, including derating for thermal runaway proximity considerations referenced in AS/NZS 5139:2019.
• EV charging DC fast-charger cables: Cables supplying DC fast chargers (up to 500 V DC typical, but architectures up to 1500 V DC are emerging) are now within scope.

The DC tables follow the same methodology as the AC tables: base current ratings at reference conditions, with derating factors applied for actual installation conditions. However, DC cables do not experience skin effect or proximity effect losses, so the DC current ratings are marginally higher than the AC equivalent for larger conductor sizes (typically above 95 mm²).

DC current rating advantage (approximate):
  16 mm² Cu XLPE:  <1% higher than AC rating
  95 mm² Cu XLPE:  ~2% higher than AC rating
 300 mm² Cu XLPE:  ~4% higher than AC rating
 630 mm² Cu XLPE:  ~7% higher than AC rating

Table 25 (grouping derating factors) has been substantially revised. The 2017 edition grouping factors assumed a relatively conservative heat dissipation model for cables on trays. Post-2017 research, including thermal finite-element studies by the University of Queensland Electrical Energy Research Group and field measurements by Ausgrid and Powerlink Queensland, identified two scenarios where the 2017 factors were inadequate:

The key finding was that the 2017 factors did not adequately account for radiative heat transfer blockage when cables are touching on a solid (unperforated) tray. Cables in the centre of a group on an unperforated tray lose less heat by radiation than the 2017 model assumed, because adjacent cables block the radiation path to the tray surface.

For perforated trays with spaced cables, the factors remain unchanged — the ventilation through the perforations provides sufficient cooling. This reinforces the engineering preference for perforated trays in high-density cable installations.

Table 27 (soil thermal resistivity derating factors) has been updated based on a decade of field measurement data from Australian conditions. The 2017 edition reference soil thermal resistivity is 1.2 K·m/W, which represents typical moist Australian soil. The 2025 edition retains this reference value but revises the correction factors for other soil conditions.

Key changes to Table 27:

• Dry sandy soil (2.5 K·m/W): Derating factor reduced from 0.80 to 0.77. Field measurements in Western Australian and South Australian arid zones showed higher-than-expected cable temperatures in dry sandy conditions.
• Very dry soil (3.0 K·m/W): New row added — derating factor of 0.71. The 2017 edition stopped at 2.5 K·m/W, which was insufficient for desert conditions encountered in mining and remote solar installations.
• Wet clay (0.7 K·m/W): Enhancement factor increased from 1.13 to 1.15. Better thermal conductivity measurements of saturated clay in coastal areas justified a slightly higher enhancement.
• Concrete-encased (1.0 K·m/W): New note clarifying that concrete thermal resistivity varies significantly with mix design. A conservative value of 1.0 K·m/W is specified unless mix-specific data is available.

Soil thermal resistivity reference values:
  AS/NZS 3008:2025  = 1.2 K·m/W  (unchanged from 2017)
  BS 7671:2018       = 2.5 K·m/W  (conservative UK assumption)
  IEC 60364-5-52     = 2.5 K·m/W  (harmonised with BS 7671)

Note: The AS/NZS reference (1.2) is less conservative than BS/IEC (2.5),
reflecting the generally better soil conditions in populated Australian areas.
In dry inland regions, AS/NZS requires significant derating.

The 2025 edition also adds an informative annex with a map of typical soil thermal resistivity zones across Australia and New Zealand, providing guidance on which Table 27 row to use when site-specific geotechnical data is not available.

Beyond the headline changes, the 2025 edition includes several smaller but technically significant updates:

• LSZH cable types: Low-smoke zero-halogen (LSZH) cables now have dedicated current rating rows in Tables 13 and 14. Previously, engineers had to use the V-90 rows as a proxy. The LSZH ratings are typically 3–5% lower than V-90 due to the slightly different insulation thermal properties.
• Fire-rated cable provisions: New informative annex addressing current rating limitations of fire-rated cables (e.g., cables to AS/NZS 3013). Fire-rated sheath systems restrict heat dissipation, requiring additional derating beyond the standard tables.
• Harmonised installation method numbering: Table 3 installation method descriptions have been aligned more closely with IEC 60364-5-52 Table B.52.1. While the column numbers remain the same (to avoid breaking existing software), the method descriptions now use terminology consistent with the IEC standard.
• Voltage drop tables update: Tables 30–42 now include reactance values at 60 Hz as well as 50 Hz, facilitating use in Pacific Island nations that operate at 60 Hz but reference AS/NZS standards.
• Aluminium conductor expanded range: Current ratings for aluminium conductors now extend down to 16 mm² (previously started at 25 mm² in some tables), reflecting the increasing use of aluminium in smaller sizes for cost-sensitive solar DC circuits.

ECalPro's cable sizing engine supports both the 2017 and 2025 editions of AS/NZS 3008. The implementation approach ensures accuracy during the transition period:

• Edition selector: Users can choose between "AS/NZS 3008.1.1:2017" and "AS/NZS 3008.1.1:2025" in the standard dropdown. The default is 2025 for new calculations.
• Parallel calculation mode: A "Compare editions" toggle runs the same input parameters against both editions simultaneously, highlighting any cases where the cable size or derating factors differ. This is invaluable during the transition period.
• Table versioning: The backend standards data is versioned. Each table entry carries an edition field (2017 or 2025), and the calculation engine selects the correct table based on the user's edition choice.
• Report output: PDF reports clearly state which edition was used, with the exact table and column references matching the selected edition. When "Compare editions" is active, both results appear side by side.

Example report reference (2025 edition):
  Current rating: 57 A
  Source: AS/NZS 3008.1.1:2025, Table 13, Column 6
  Grouping factor: 0.68
  Source: AS/NZS 3008.1.1:2025, Table 25, Row "6 circuits", Column "Unperf. tray, touching"

Example report reference (2017 edition, same scenario):
  Current rating: 57 A
  Source: AS/NZS 3008.1.1:2017, Table 13, Column 6
  Grouping factor: 0.73
  Source: AS/NZS 3008.1.1:2017, Table 25, Row "6 circuits", Column "Unperf. tray, touching"

Result: 2025 edition requires next cable size up (4.0 mm² → 6.0 mm²)

During the transition period, many projects already in design or under construction are contractually required to use the 2017 edition. ECalPro fully supports this:

• Existing projects retain their edition: Projects created before the 2025 edition was added to ECalPro retain the 2017 edition as their default. The edition is stored per-project and per-calculation.
• Regulatory grace period: Until the next edition of AS/NZS 3000 formally references the 2025 edition, either edition is legally acceptable. Check with your state or territory regulator for jurisdiction-specific guidance:
  • Energy Safe Victoria (ESV)
  • NSW Fair Trading
  • Electrical Safety Office Queensland (ESO)
  • EWRB New Zealand
• Audit trail: Every calculation stores the edition used at the time of calculation. Even after ECalPro defaults to the 2025 edition, historical calculations remain traceable to the 2017 tables.

For engineers who want to future-proof their designs, we recommend running the "Compare editions" mode. If the 2025 edition requires a larger cable, it may be prudent to specify the larger size now to avoid rework when the 2025 edition becomes mandatory.

If you are transitioning from the 2017 to the 2025 edition, review the following for each active project:

1. Check grouping factors: Any installation with 3+ circuits on unperforated cable trays should be recalculated with the 2025 Table 25 factors. This is the change most likely to affect cable sizes.
2. Review buried cable designs in arid areas: If soil thermal resistivity exceeds 2.0 K·m/W, the 2025 derating factors are more stringent. Remote mining and solar installations are most affected.
3. Check DC solar string cables: If you were sizing 1500 V DC cables using AC tables with manual corrections, verify the cable size against the new DC-specific tables. Results may differ.
4. Update specification templates: Ensure project specifications reference "AS/NZS 3008.1.1:2025" rather than "AS/NZS 3008.1.1:2017" for new projects. Both are acceptable during transition, but specifying the 2025 edition avoids ambiguity.
5. Verify LSZH cable ratings: If using LSZH cables and previously referencing V-90 rows, check whether the dedicated LSZH rows in the 2025 edition give different (typically slightly lower) ratings.