Copper vs aluminium conductors in Australian cables
How copper and aluminium cable candidates differ for voltage drop, loss, cost, termination and installation review.
What The Material Changes
Copper and aluminium are not interchangeable labels on the same metric cable size. The conductor material changes resistance, voltage drop, cable loss, weight, termination details, available products and cost assumptions.
In Australian cable schedules, the same 35 mm2 size label can point to different electrical and mechanical behaviour depending on whether the cable is copper or aluminium, and depending on the actual cable construction and product data.
Electrical Comparison Points
Voltage-drop and loss comparisons need material-specific resistance data, usually entered as ohm/km or as a cable data value sourced from the project, manufacturer or reviewed document. A copper resistance value must not be reused for an aluminium candidate.
For a simple entered-resistance comparison, AUWiring calculates voltage drop, percent drop, cable loss and material cost from the values entered by the user. That makes the trade-off visible, but it does not make the material choice.
| Field | Copper candidate | Aluminium candidate |
|---|---|---|
| Resistance | Enter copper resistance or voltage-drop data for the actual cable. | Enter aluminium resistance or voltage-drop data for the actual cable. |
| Voltage drop | Often lower for the same nominal size when source data confirms it. | Often higher for the same nominal size, so it needs its own data. |
| Cable loss | Calculated from current and voltage drop. | Calculated separately from aluminium data. |
| Material cost | Enter project or supplier cost per metre. | Enter project or supplier cost per metre. |
| Termination | Product-compatible lugs and instructions still apply. | Lug, jointing and compatibility checks usually need explicit attention. |
Worked 80 A Comparison
Consider two entered candidates for a 70 m run carrying 80 A on a 400 V basis. The copper candidate uses 0.727 ohm/km. The aluminium candidate uses 1.15 ohm/km. In a simplified two-conductor comparison:
- Copper voltage drop is about 8.14 V, or 2.04% of 400 V.
- Aluminium voltage drop is about 12.88 V, or 3.22% of 400 V.
- Cable loss is about 651 W for the copper candidate and 1030 W for the aluminium candidate.
- At AUD 11.00/m for copper and AUD 7.50/m for aluminium, the entered material cost is AUD 770 versus AUD 525.
That example shows the trade-off. It does not settle current-carrying capacity, termination, mechanical suitability, route space or installation method.
| Field | 35 mm2 copper candidate | 35 mm2 aluminium candidate |
|---|---|---|
| Material input | Copper data set. | Aluminium data set. |
| Voltage-drop basis | Copper resistance or voltage-drop data for the chosen cable construction. | Aluminium resistance or voltage-drop data for the chosen cable construction. |
| Termination note | Product-compatible lugs and instructions still apply. | Lugs, jointing method and compatibility need explicit checking. |
| Review outcome | Not interchangeable with aluminium simply because the size label matches. | Not interchangeable with copper simply because the size label matches. |
Mechanical And Installation Questions
Electrical arithmetic is only one part of the comparison. Aluminium can change route weight, bending, termination hardware, corrosion controls, enclosure space and product availability. Copper can change cost, weight and installation handling. Both materials still need product data and project requirements.
Keep conductor material beside cable size, current, route length, voltage basis, resistance source, lug or termination note and installation method. If material-specific data is missing, stop the comparison rather than borrowing values from another cable.
Next checks
- Use the copper aluminium comparison calculator when both material candidates have their own resistance, route, current and cost values.
- Use the voltage-drop calculator when only one cable run is being checked against a project target.
- Use the cable-size workflow before carrying either material into current-carrying capacity, derating or protection review.
Boundaries
- This page does not choose conductor material or cable size.
- It does not provide current-carrying capacity values, supplier prices or termination instructions.
- Manufacturer data, lugs and terminals, corrosion controls, route conditions, project documents and competent review remain controlling inputs.