MYTH: Copper Is Always Better Than Aluminium for Power Cables
For cables 95mm² and above, aluminium is standard worldwide. 70% lighter, 40-60% cheaper per ampere. The right answer depends on the application.
February 26, 2026
The Myth
"Always specify copper. Aluminium is inferior — it was banned after those house fires in the 1970s."
This belief is so widespread that many junior engineers reflexively reject aluminium without analysis. The irony: every high-voltage transmission line you've ever seen uses aluminium. Every utility transformer is connected with aluminium. The global power grid runs on aluminium.
The Reality
The 1970s aluminium wiring problems were caused by small gauge solid aluminium (15A branch circuits) with improperly rated terminations. The aluminium-to-brass connections oxidized, created hot spots, and caused fires. This is a termination problem, not a conductor material problem.
For power distribution cables 95mm² and above, aluminium is the standard engineering choice worldwide:
| Factor | Copper 95mm² | Aluminium 150mm² | Winner |
|---|---|---|---|
| Current rating (Table 3/8) | 238A | 242A | Comparable |
| Weight per metre | 1.10 kg/m | 0.53 kg/m | Al (52% lighter) |
| Approximate cost per metre | $28/m | $16/m | Al (43% cheaper) |
| Bending radius | 8×D | 8×D | Tie |
| Corrosion resistance | Excellent | Good (oxide layer self-healing) | Cu (slight) |
The aluminium cable is one size larger (150 vs 95mm²) to achieve equivalent current capacity, but it's still significantly lighter and cheaper. At 240mm² and above, the cost advantage widens further.
When Copper IS the Right Choice
Copper is superior for specific applications:
- Small sizes (<16mm²): Flexibility, termination reliability, and space constraints make copper the clear choice for branch circuits and control wiring
- Flexible cables: Aluminium lacks the fatigue resistance for flexible or trailing cables
- Corrosive environments: In coastal or chemical plant environments, aluminium's oxide layer may be insufficient without additional protection
- Space-constrained installations: Where the larger aluminium cable won't physically fit in the available tray or conduit
- High-vibration areas: Aluminium's lower fatigue strength makes it unsuitable where mechanical vibration is present
The Economic Analysis
For a typical 200m feeder cable run rated at 300A:
| Option | Cable Size | Material Cost | Installation Labour |
|---|---|---|---|
| Copper | 150mm² | ~$11,200 | Higher (heavier) |
| Aluminium | 240mm² | ~$7,400 | Lower (lighter) |
| Saving | $3,800 (34%) | Additional saving |
Across a 50-cable industrial distribution project, aluminium saves $150,000–$200,000 in cable material costs alone, plus labour savings from handling lighter cables.
The Modern Standard
Per AS/NZS 3008.1.1:2017, aluminium cables are fully covered in Table 8 with identical installation methods and derating factors as copper. BS 7671 Appendix 4 provides aluminium conductor resistances. IEC 60228 specifies aluminium conductor requirements.
No standard "prefers" copper. The choice is an engineering and economic decision, not a safety one — provided proper aluminium-rated terminations (marked AL-CU or AL) are used per manufacturer specifications.
Bottom Line
Copper isn't always better. Aluminium isn't inferior. The right choice depends on cable size, application, environment, and cost. For feeder cables 95mm² and above, default to aluminium unless a specific technical reason demands copper. Your project budget will thank you.
Compare for yourself: Run copper vs aluminium cable selections in the Cable Sizing Calculator.
Frequently Asked Questions
What standards govern cable sizing calculations?
The primary standards are AS/NZS 3008.1.1:2017 (Australia/NZ), BS 7671:2018 (UK), IEC 60364-5-52 (International), and NEC Article 310 (USA). Each has different assumptions for ambient temperature, installation methods, and derating factors.
Why do different standards give different cable ratings?
Standards differ in reference ambient temperature (AS/NZS uses 40°C, BS 7671 uses 30°C), test conditions, grouping factor calculations, and installation method classifications. A 50mm² XLPE cable can vary by 15% between standards.
How do I apply derating factors correctly?
Derating factors must be applied multiplicatively: Final Rating = Base Rating × k₁ (ambient) × k₂ (grouping) × k₃ (thermal insulation) × k₄ (ground temp). Each factor comes from specific tables in the relevant standard.
Related Articles
- Cable Sizing Calculator - Interactive calculator with standards compliance
Try It Yourself
Run the calculations from this article using our free calculators: