Is aluminum wiring still allowed?

Aluminum wiring is still allowed by the NEC, and utilities and electricians install it every day. Service entrances and large feeders are routinely aluminum because it costs far less than copper at big sizes.

The bad reputation comes from a specific product: small solid aluminum branch wiring from the mid 1960s to mid 1970s, which loosened at receptacles and switches and caused fires.

Modern AA-8000 series alloy, used at feeder sizes with rated lugs and antioxidant paste, does not have that problem. What nobody installs anymore is 15 and 20 amp aluminum branch circuits.

Aluminum needs one size larger conductor than copper for the same load, so the sizing math changes.

The aluminum wire ampacity calculator shows what each aluminum size actually carries under the current code.