Material Insights · Understanding the Material World

Aluminium and Underground, submarine and superconducting cables

Buried and subsea power cables need a metal conductor, and aluminium competes with copper for it: aluminium needs a larger cross-section for the same rating but is far lighter and usually much cheaper, so the copper to aluminium price gap decides the choice for many projects.

Aluminium (commodity) and Underground, submarine and superconducting cables (energy): 4 relationships.

How they are linked

1. Conductor metal

Physical flow · Direct · Aluminium → underground and subsea cables

Every power cable has a metal core that carries the current, and aluminium is one of the two standard choices for it, alongside copper.

  • 2,500 mm² aluminium conductor giving nearly the same rating as a 2,000 mm² copper one (French grid example)
  • 3,000 and 4,000 mm² aluminium conductor sizes now offered by manufacturers
  • around 48% share of aluminium consumed in India used in power transmission and distribution

Underground cables are sized for heat: losses of around 30 W per metre must escape through the soil, so a larger aluminium core with lower losses can be the cheapest choice over a cable's life. French grid data show cables run below 60% of their maximum rating more than 95% of the time, which favours designs optimised for life-cycle cost rather than peak load.

Sources: Power and Cables (Frédéric Lesur); AlCircle

2. Aluminium or copper core

Substitution · Medium · Aluminium can replace copper in many cables

Copper conducts better, so a copper cable is thinner for the same current, but copper is much heavier and dearer, so aluminium wins where space allows a larger core.

  • 1.64 times copper's electrical conductivity relative to aluminium
  • over three times copper's weight relative to aluminium, per the source's comparison
  • up to five times copper's price relative to aluminium at times this century

Copper keeps an edge where space is tight or where long experience matters, and a lack of qualification experience is a barrier for aluminium in the very largest cable systems. When copper is expensive relative to aluminium, utilities and developers have more reason to qualify and specify aluminium cores.

Sources: Power and Cables (Frédéric Lesur)

3. Aluminium in offshore wind cables

Transition · Rising · Offshore wind opens new aluminium cable uses

Floating and deep-water wind farms need cables that hang in the water column, where a lighter core reduces load on floats and fittings, so aluminium's low weight has extra value.

Research on dynamic high-voltage cables for floating wind found aluminium conductors feasible for low-weight, low-cost and deep-water use, and aluminium cores are increasingly proposed for static subsea cables for the same reasons. The share of aluminium in subsea cable will depend on how quickly these designs are qualified.

Sources: University of Exeter

4. Price link: conductor metal

Cost and price · Strong · Both ways

Aluminium is a large part of the material cost of many cables, so cable prices follow it, and substitution with copper ties cable costs to both metals.

  • 0.32 monthly change correlation
  • 0.75 12-month change correlation
  • 0.63 fitted elasticity

The cable index follows aluminium with a lag of about a month, and yearly moves are closely tied. Cable makers pass metal costs through over time, so a jump in metal price shows up in cable prices within months rather than at once.

Sources: Material Insights (World Bank, FRED, IMF data)

For investors

Key learnings

  1. Aluminium cable needs a cross-section about a quarter larger than copper for the same rating (2,500 against 2,000 mm² in a French example) but costs much less, so a wide copper to aluminium price ratio lifts aluminium's share in cable.
  2. Cable prices follow aluminium with about a month's lag and a 0.75 yearly correlation, so cable makers without metal pass-through clauses carry the metal price risk on fixed-price orders.
  3. Floating offshore wind is a new outlet where aluminium's light weight matters, but qualification of large aluminium systems is slow.

What to track

  • Copper to aluminium price ratio: A higher ratio favours aluminium cores in new cable tenders (Daily · LME)
  • Conductor material in utility and offshore wind cable awards: Shows whether substitution is moving into orders (Quarterly · cable makers' results, tenders)
  • Aluminium rod premiums: Sets the cost of cable-grade aluminium (Monthly · producer price lists)

For policymakers

Key learnings

  1. Specifying aluminium where it is technically suitable can cut the cost of grid cables and reduce reliance on imported copper.
  2. Qualification standards decide where aluminium cores are accepted, so utilities and standards bodies hold a key lever.
  3. India's power transmission and distribution sector already uses about 48% of the aluminium consumed in the country, so cable and conductor standards have a large effect on domestic metal demand.

What to track

  • Cable standards and utility specifications for aluminium cores: Wider acceptance allows more substitution (As revised · Bureau of Indian Standards, utilities)
  • Copper and aluminium imports: Shows how far domestic metal covers cable demand (Monthly · Ministry of Commerce)

India

The power transmission and distribution sector uses about 48% of the aluminium consumed in India, so grid building and cable specifications are central to domestic aluminium demand.

Sources

  1. Electrify the future: can aluminium really beat copper in underground power cables?, Power and Cables (Frédéric Lesur) (2021)
  2. Dynamic HV cables with Al conductors for floating offshore wind turbines: a cost and behaviour comparative study, University of Exeter (2020)
  3. Price correlation, Material Insights, Material Insights (World Bank, FRED, IMF data)
  4. India's ₹9.15 lakh crore power grid push could drive new aluminium demand, AlCircle (2026)