Comparison

Copper vs Aluminum Feeders: How to Choose

Aluminum is about 30% of the weight of copper and costs less per ampere on large feeders, but needs larger conductors and careful terminations. Compare them side by side.

Electrical & Power · Last reviewed October 15, 2026

Short answer: copper is the default for branch circuits and small feeders. Aluminum is common for large feeders and service conductors, where its lower cost and weight outweigh the larger size, provided the terminations are rated and installed correctly.

	Copper	Aluminum
Conductivity	Higher (reference, 100%)	About 61% of copper by volume
Size for the same ampacity	Smaller	Typically two AWG sizes larger, or about 1.6 times the cross-section
Density	About 8.96 g/cm³	About 2.70 g/cm³, roughly 30% of the weight of copper for the same size
Material cost	Higher and more volatile	Lower. The saving is largest on big feeders
Terminations	Standard lugs	Lugs and devices must be marked for aluminum (AL, CU/AL or AL9CU). Oxide film, cold flow and thermal expansion need correct torque and sometimes an antioxidant compound
Mechanical	Stronger, less creep	Softer. More prone to creep under a loose connection
Typical use	Branch circuits, control wiring, small feeders, tight spaces	Service entrance, large feeders, busway, overhead lines

How to choose

Look at the size of the circuit. Below about 100 A, copper is usually the practical choice. Above 200 A, aluminum feeders often save money.
Check the equipment lugs. Every termination at both ends must be rated for the conductor material and the temperature.
Compare the installed cost, not the metal price: bigger conduit, bigger lugs and more labor can offset part of the saving.
Check voltage drop. The larger aluminum conductor has about the same resistance as the smaller copper one, so voltage drop is similar for equal ampacity, but compare them in the calculation.
Check the code for restrictions. For example, aluminum is not generally permitted for some applications, and rules differ by jurisdiction.

Common mistakes

Using copper ampacity values for an aluminum conductor.
Terminating aluminum on a copper-only lug.
Skipping the torque specification, or not re-checking it. Aluminum connections depend on correct torque.
Mixing the old and new aluminum alloys. Modern AA-8000 series alloy conductors replaced the older alloy used in some branch circuits, and the older problems with it do not apply to the current alloy.

Two scenarios

A 400 A feeder run 300 ft from the service to a distribution board. At this size aluminum conductors cost much less than copper, and the larger conduit and lugs add little. Aluminum is the usual choice, provided the lugs at both ends are rated for it.

A 30 A branch circuit to a machine in a tight panel. The conductor is small, the metal cost is minor, and aluminum would need larger lugs and bring termination risk with little saving. Copper is the better choice.

Cost and life cycle

Metal price: copper prices are higher and more volatile. The saving from aluminum is greatest on large feeders.
Labor: aluminum needs correct torque, and some installers apply an antioxidant compound. A mistake costs more than the metal saved.
Weight: aluminum is much lighter, which cuts handling effort on large conductors and long overhead runs.
Standards: check the code for conductor material restrictions and the ampacity tables for the actual insulation.

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Questions

Is aluminum wiring a fire hazard?

The problems reported with older aluminum branch-circuit wiring came from the alloy used at the time and from connections to devices not designed for it. Current AA-8000 alloy conductors with listed terminations are used safely for feeders and services.

What size aluminum replaces 4/0 copper?

Use the ampacity table for the actual insulation, temperature and installation, not a rule of thumb. As a rough guide, aluminum needs about two sizes up.

Does aluminum have a lower ampacity?

For the same size, yes: the ampacity tables give lower values for aluminum. A larger aluminum conductor is used to carry the same current.

Can I mix copper and aluminum in one splice?

Only with a connector listed for both materials. Direct contact between the two metals can lead to corrosion.

Is aluminum used in building wire for small circuits?

Branch-circuit wiring in buildings is almost always copper. Aluminum is mainly used for feeders, services and utility lines.

Educational material. Examples use simplified, hypothetical inputs and are not a design, a construction document or professional engineering advice. Confirm requirements with the codes and standards adopted where the work is built and with a licensed engineer.

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