Copper or Aluminium? Where Each Conductor Actually Belongs

The copper-versus-aluminium argument has outlived most of the people who started it. The physics hasn’t moved: aluminium’s resistivity is about 64% higher, so an aluminium conductor needs to be roughly one size bigger to carry the same current. Everything sensible about choosing between them follows from that one number — and from where the cable is going.

Inside a house, it’s copper, and not out of snobbery. Final circuits live in small conduits, land on accessory terminals designed around copper, and get disturbed every time someone changes a switch. Copper’s ductility and its stable terminations are why Indian house wire is flexible class-5 electrolytic copper — every APAR house wire, from Shakti FR to Anushakti Fire Protekt, is built that way. Below about 16 sq mm, frankly, aluminium isn’t worth the trouble: small aluminium terminations age badly and the size penalty buys you nothing.

Step up to feeder sizes and the argument flips just as decisively. A 240 sq mm aluminium XLPE feeder weighs a fraction of its copper twin and costs far less; go one size up and you’ve bought the resistance back. This is why utilities distribute on aluminium, why overhead lines are aluminium outright — conductor weight sets the sag, and sag sets the tower bill — and why LV XLPE power cable is stocked in both metals to 1000 sq mm. Even aluminium multicore earns its keep on long panel feeds and pump runs where distance makes copper extravagant.

So: copper below 16, arithmetic above it. Same load, aluminium one size up, compare the installed cost. Feeders usually go to aluminium; anything dense, flexible or frequently touched stays copper.

One last habit worth stealing from our datasheet-auditing work. When you compare brands, check the aluminium resistance figures against IS 8130. We have seen printed datasheets quoting copper-level resistance for small aluminium sizes — which is physically impossible; pure aluminium at 6 sq mm cannot beat 4.71 Ω/km, full stop. The honest values (1.91 at 16 sq mm, 1.20 at 25) are on our comparison table. A datasheet that can’t get physics right is telling you about the factory behind it.