Why the question keeps coming up
Copper and aluminium together make up roughly 80% of the cost of a typical wire or cable product, according to listed cable makers' disclosures, and copper is the larger share. When the LME three-month copper price reached an intraday record of USD 14,875 per tonne on 10 September 2026 (Fastmarkets), and was still around USD 14,315 per tonne on 21 October 2026, many buyers asked whether aluminium conductors could replace copper on feeders and mains. For some circuits the answer is yes. For others the larger size, the joints and the local wiring rules cancel out the saving.
The desk does not quote prices in articles, and nothing here is a price comparison. What follows is the technical side a buyer needs before asking partner plants for both options.
Resistance: why aluminium needs a bigger size
Aluminium conducts less well than copper, so for the same nominal cross-section it has a higher resistance. IEC 60228 makes this visible in its tables. The maximum DC resistance at 20 degrees C for Class 2 conductors is:
| Nominal size | Copper Class 2 | Aluminium Class 2 |
|---|---|---|
| 10 mm2 | 1.83 | 3.08 |
| 16 mm2 | 1.15 | 1.91 |
| 25 mm2 | 0.727 | 1.20 |
| 35 mm2 | 0.524 | 0.868 |
| 50 mm2 | 0.387 | 0.641 |
| 70 mm2 | 0.268 | 0.443 |
| 95 mm2 | 0.193 | 0.320 |
| 120 mm2 | 0.153 | 0.253 |
Read across the table and the pattern is clear: aluminium resistance is about 1.6 times copper resistance at every size, so an aluminium conductor matches a copper conductor one to two standard sizes smaller. Aluminium 95 mm2 (0.320) is lower than copper 50 mm2 (0.387) but higher than copper 70 mm2 (0.268); aluminium 120 mm2 (0.253) is just below copper 70 mm2. Because voltage drop and heating both follow resistance, a switch from copper to aluminium usually means stepping up the size. The exact step depends on the current rating per installation method to IEC 60364-5-52, BS 7671 or NEC as applicable, which the project engineer confirms; this article does not give current ratings.
Weight, diameter and handling
Aluminium is roughly a third of the density of copper, so even after upsizing, an aluminium cable is much lighter per metre. The two reference constructions on this site illustrate the scale, though they are different sizes: the 0.6/1 kV Cu/XLPE/PVC 4x25 mm2 reference model weighs about 1,292 kg/km with an OD of about 25 mm, while the 0.6/1 kV Al/XLPE/PVC 4x95 mm2 reference model on the aluminium cables page weighs about 1,907 kg/km with an OD of about 40 mm. The aluminium cable carries almost four times the nominal cross-section for under one and a half times the weight.
The flip side is diameter. A larger conductor means a larger cable, which affects tray fill, duct size, gland sizes, bending radius and how many metres fit on a drum. Lighter drums are easier to lift and ship, but more drums may be needed for the same route length. These points belong in the comparison before anyone looks at price per metre.
Weight also feeds straight into freight and inspection. Shipping is often limited by drum weight rather than by volume for copper cable, while aluminium drums tend to fill space before they reach weight limits. At pre-shipment inspection, measured weight per kilometre is a quick cross-check against the datasheet for both metals: a copper cable that is noticeably light for its size, or an aluminium cable sold as copper, shows up on the scale before the resistance bridge is even connected. The desk records drum gross and net weights alongside the resistance values so the two checks can be read together.
Joints and terminations: where aluminium needs care
Most field problems with aluminium conductors come from terminations, not from the cable itself. Three properties drive the extra care:
- Oxide layer: aluminium forms a hard, poorly conducting oxide film within moments of being exposed. Lugs and connectors for aluminium are designed to break through it, often with a contact compound supplied by the lug maker.
- Creep and expansion: aluminium deforms slowly under clamping pressure and expands more with heat than copper, so bolted joints must use lugs and torque values specified for aluminium.
- Galvanic contact: aluminium touching copper busbars in damp conditions corrodes; bimetallic lugs or connectors rated for both metals avoid direct contact.
None of this makes aluminium unsafe. Utilities have used aluminium conductors on distribution networks for decades. It does mean the BOQ must include the right lugs, the installers must follow the lug maker's instructions, and switchgear terminals must be rated for aluminium.
Where each metal belongs
Partner plants typically supply aluminium power cable from 10 mm2 in single core and from 10 to 400 mm2 in multicore; small-section aluminium is not offered. That matches practice: aluminium makes sense on larger feeders, mains, sub-mains, utility distribution and solar farm AC collection, where the conductor is large, the run is long and the joints are few. Copper remains normal for final circuits, control and instrumentation cables, flexible cords and anything with many small terminations. In the US, NEC 310.3 sets the minimum size for aluminium and copper-clad aluminium building conductors at 12 AWG, against 14 AWG for copper.
| Factor | Copper | Aluminium |
|---|---|---|
| Resistance per size | Lower | Higher; usually upsized |
| Weight per metre | Higher | Lower, even after upsizing |
| Cable diameter | Smaller for the same duty | Larger |
| Terminations | Standard lugs | Aluminium or bimetallic lugs, specified torque |
| Typical uses | Final circuits, control, cords | Feeders, mains, utility networks |
How to ask for both options
If you want to compare, ask partner plants to quote copper and aluminium constructions that meet the same electrical duty, not the same nominal size. Give the project engineer's sizes for each metal, or the inputs needed to size them, as described in the cable size selection basics. The desk then asks each plant for conductor resistance records per drum, because an aluminium conductor is checked against the aluminium column of IEC 60228 exactly as a copper one is checked against the copper column. The conductor materials page covers tinned copper and other options, and the quote form lets you request copper and aluminium side by side.