Cost and weight are why aluminum keeps showing up on bigger work
Copper is the premium answer. Aluminum is the cost-control answer. Once feeder and service conductors get large, aluminum becomes attractive because it is dramatically lighter and cheaper to buy, move, and pull.
That does not make it free. The moment you save money on conductor cost, you take on larger wire size, larger bending radius, and more careful termination work.
Ampacity and size: why the aluminum answer is usually bigger
| Target Ampacity | Typical Copper | Typical Aluminum | Common Use |
|---|---|---|---|
| 60A | #6 Cu | #4 Al | Small feeder |
| 100A | #3 Cu | #1 Al | Sub-panel feeder |
| 200A | 2/0 Cu | 4/0 Al | Residential service |
The exact answer still depends on conditions of use, but the pattern stays the same: aluminum usually needs more conductor area to do the same job.
Voltage drop is where a cheap material swap can stop being cheap
Long runs punish aluminum faster because its resistance is higher. That means a feeder that passes with copper may need the next size up in aluminum just to keep voltage drop reasonable.
This is why the right workflow is usually wire size first, then voltage drop second. If the material changes anywhere in that conversation, rerun both checks.
Where each one wins in real electrical work
- Copper wins on small branch circuits, compact raceways, and voltage-drop-sensitive work.
- Aluminum wins on cost-sensitive large feeders and many service-entrance jobs.
- Copper is easier to live with when termination space is tight.
- Aluminum becomes more attractive as conductor size and project budget both grow.
Termination checks matter more with aluminum
If you choose aluminum, stop treating the conductor swap like the entire decision. Verify the terminals are listed for aluminum, use the manufacturer torque values, and follow the connector requirements for the actual lugs and terminations in the equipment.
Frequently Asked Questions
Is copper always better than aluminum?
Not automatically. Copper is more compact and performs better for voltage drop, but aluminum is lighter and cheaper at feeder and service sizes. The better answer depends on the job, not on habit.
Why does aluminum usually need a larger conductor size?
Because aluminum has higher resistance than copper. To carry the same current and control voltage drop, it usually needs more cross-sectional area.
Should I use aluminum for small branch circuits?
Usually no. Modern aluminum is valid in the right applications, but small branch-circuit work is still overwhelmingly copper in the field.
Do I need to rerun the voltage-drop calculation if I switch materials?
Yes. Material is not a cosmetic selection. Switching from copper to aluminum can materially change the voltage-drop result and the final conductor size.
Turn It Into A Real Size
Wire Size Calculator
Run the live conductor-sizing workflow when the material choice needs to turn into an actual wire answer.