Aluminium or copper for an EV charger circuit

The short version is that this is a feeder question rather than a branch circuit question. For the 30 or 40 feet of conductor between your panel and a charger on the garage wall, copper is easier, familiar to every inspector, and the money saved by going to aluminium is small enough that it is not worth the extra handling. For the 120 feet of feeder out to a detached garage subpanel, aluminium can cut the conductor cost by two thirds, and that is a difference measured in hundreds or thousands of dollars.

The reason the two cases diverge is that copper price scales with conductor size, and feeders are large. A 6 AWG conductor is not expensive in either material. A 1/0 conductor is, and that is where the material choice becomes the largest single line in the parts list.

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Why aluminium carries less current

Aluminium is a poorer conductor than copper by roughly 40 percent for the same cross sectional area, so a given conductor size carries less current before it reaches its temperature limit. It is also lighter and considerably cheaper per pound, and it is these three facts together that decide every practical question about it. You trade size for money.

The 75 degree Celsius column is used here because it is the column that governs almost every residential installation. Breakers, lugs and equipment terminals in a house are typically listed at 75 degrees even when the conductor insulation is rated for 90, and the circuit is limited by the lowest-rated component in it. The full three-column table for both materials is on the wire gauge ampacity chart.

The practical equivalents

In day to day terms, aluminium goes up one to two standard sizes to match a copper conductor. These are the pairs that come up in a home charging project, with the caveat that your electrician sizes the actual conductor against your run length, ambient temperature and terminal ratings.

Notice where the interesting rows are. At 50 and 60 amps you are moving from 6 AWG to 4 AWG, and the price difference across a short run is not the decisive factor. At 100 and 200 amps you are moving between conductors that cost several dollars a foot in copper, and the aluminium version of the same feeder can be a third of the price. That is why service entrance conductors are almost universally aluminium, and why utilities have used it for overhead service drops for decades.

Voltage drop, which is the other half of the sizing question

On any run past about 75 feet, voltage drop rather than ampacity usually picks the conductor. The design target most electricians work to is three percent on a branch circuit, which is a recommendation in the code rather than a hard requirement, and it is exactly the sort of recommendation that quietly disappears from a competitive quote. Here is a 100 foot run carrying 48 amps in both materials.

The pattern to take from that table is that once you are sizing for drop rather than for heat, the aluminium conductor grows but so does the copper one, and the price ratio between them barely changes. Run your own numbers in the voltage drop calculator, and if the run is genuinely long, read long runs and voltage drop before accepting a quote that has not mentioned the subject.

The terminations are the whole risk

Every credible objection to aluminium is really an objection to badly made aluminium terminations, and the history matters because it explains what the rules are for. In the late 1960s and early 1970s, solid aluminium branch circuit conductors were connected to receptacles and switches designed and listed for copper. Aluminium expands and contracts more than copper with temperature, it creeps under sustained pressure, and its surface oxide is a poor conductor. Those three together loosened connections, which raised resistance, which produced heat, which loosened them further.

Three things changed. The alloy changed to the AA-8000 series, which creeps far less. Terminals began to be listed and marked for the materials they accept, AL-CU on lugs and breakers and CO/ALR on devices. And preparation practice standardised: wire brush the conductor, apply an oxide inhibitor compound, and torque the termination to the value printed on the equipment.

None of that makes aluminium a homeowner material. It makes it a material with a defined procedure, where skipping a step has consequences that appear slowly and invisibly inside a lug. If your electrician proposes aluminium for a feeder, the questions worth asking are whether the panel lugs are rated AL-CU, what torque value is being used, and whether inhibitor is being applied. Good answers to those three are the whole of the safety case.

What an aluminium termination actually needs

The compound is a few dollars and it is the step that separates a good aluminium connection from the reputation aluminium has.

The part nobody should skip

ILSCO

ILSCO Oxide Inhibitor Compound

$14.75

Oxide inhibitor for aluminium terminations, in a small quantity for one or two connections. The oxide layer that forms on bare aluminium is a poor conductor, and inhibitor compound is what stops it reforming inside a lug after the connection is made.

Use

Aluminium lugs

Size

1 oz

Type

Oxide inhibitor

Cost

Under $15

Trade-off A small tube, so a large job needs the bigger container instead.

Check price

For a bigger job

Ideal Industries

Ideal Noalox Anti-Oxidant Compound

$59.88

The larger 8 ounce container of the same class of compound, for a service upgrade or a subpanel where several large terminations are being made at once.

Use

Aluminium lugs

Size

8 oz

Type

Anti-oxidant

Brand

Ideal

Trade-off Far more than one circuit needs, so buy the small tube for a single termination.

Check price

The copper comparison

Southwire

Southwire 6/3 NM-B Cable, 125 ft

$417.95

Copper 6/3 with ground in a 125 foot roll, the comparison point. It is the easy, familiar, universally accepted option, and on this length it is also several hundred dollars of copper.

Size

6/3 with ground

Material

Copper

Type

NM-B

Length

125 ft

Trade-off NM-B cable is for dry interior locations, so it is not the right product for a buried feeder.

Check price

Paid links. Prices shown when researched and change without notice.

Where aluminium belongs in a home charging project

The feeder to a detached garage

This is the clearest case. A 100 amp feeder running 120 feet to a garage subpanel is a large conductor over a long distance, and it is often direct buried or in underground conduit where aluminium XHHW-2 is entirely at home. The subpanel arrangement itself, and why it usually beats three separate home runs, is in subpanel for an EV charger and the trenching side is in detached garage EV charger.

A service upgrade

If you are going from 100 to 200 amp service, the service entrance conductors are almost certainly going to be aluminium, and that is normal rather than a corner being cut. The cost of that job lives in utility coordination, meter equipment, permits and labour rather than in the conductor. The full picture is in panel upgrade for an EV charger.

Not the branch circuit inside the house

For the 20 to 40 feet between a panel and a charger, use copper. The saving is small, the conductor is easier to work in a box, and you avoid an extra requirement on every device it touches. The exception is a long interior run where the size has already grown for voltage drop, and even there the decision belongs to the electrician rather than to a table.

Never as a repair to existing aluminium branch wiring

If your house has 1970s solid aluminium branch circuits, that is a specific situation with specific remediation methods, and adding an EV charger to a panel full of it is a conversation to have before you buy any hardware at all. Have an electrician evaluate the existing wiring first.

What it actually saves

On the tier three install priced in the panel upgrade buildout, the feeder is the second largest hardware line. A copper feeder for that job is a several hundred dollar item, and the equivalent aluminium conductor with the extra size accounted for is typically a fraction of it. Across a 150 foot run to an outbuilding, the difference has been enough on real quotes to pay for the trenching.

Set against that, aluminium adds a small amount of labour: the conductor is stiffer to handle at the larger size, the terminations take a little longer, and the compound is one more thing to buy. On a short run that overhead eats the saving. On a long feeder it disappears into the noise. That crossover, somewhere around the point where you are pulling a feeder rather than a branch circuit, is the single most useful thing to take from this page.

How this page was researched

Ampacity figures are reproduced from published National Electrical Code tables for copper and for aluminium and copper-clad aluminium conductors, at the 60, 75 and 90 degree Celsius terminal columns. Resistance values used for voltage drop come from published conductor property tables. Product information comes from manufacturer documentation and listed certifications. We do not perform hands-on testing and never claim to.

In a real installation, allowable ampacity is further adjusted for ambient temperature, the number of current-carrying conductors in a raceway, the continuous load rule and the terminal temperature ratings of the breaker and the equipment, and any of those can move the answer down a size. Local amendments to the code vary by jurisdiction, including on where aluminium may be used. Treat everything here as planning information rather than as an electrical specification.

Where to go next

For the branch circuit itself, wire size for an EV charger covers copper sizing in detail, and the wire gauge calculator works it out for your run. If you are weighing a subpanel against a home run, start with the panel load calculator, and if the panel is the constraint, load management vs panel upgrade is the cheaper conversation to have first.

Common questions

Can you use aluminium wire for an EV charger circuit?

Yes, where the conductors, the terminals and the local code all permit it. Modern aluminium building wire is an AA-8000 series alloy, which is a different material from the 1970s solid aluminium branch circuit wiring that earned the reputation. It is used routinely for service entrance conductors and for subpanel feeders. The requirements are that the conductor is sized larger than the copper equivalent, that every termination is rated for aluminium, and that terminations are prepared with an oxide inhibitor and torqued to specification.

How much bigger does aluminium wire need to be than copper?

Usually one to two standard sizes for the same ampacity. At the 75 degree Celsius column, 6 AWG copper carries 65 amps and 6 AWG aluminium carries 50, so a 60 amp circuit that takes 6 AWG copper takes 4 AWG aluminium. For a 100 amp feeder, 3 AWG copper becomes 1 AWG aluminium. The larger conductor is still usually cheaper, which is the entire reason aluminium is used.

Is aluminium wiring safe?

Correctly specified and correctly terminated, it is used every day in service entrances and feeders across the country. The historical problem was solid aluminium branch circuit wiring in the 1960s and 1970s connected to devices designed for copper, where the combination of thermal expansion, creep and oxidation produced loose, hot connections. The material changed, the terminals changed, and the preparation practice changed. What has not changed is that terminations must be rated for aluminium and torqued correctly.

Should I use aluminium for a short garage charger circuit?

Usually not. On a 30 foot run to a 60 amp charger circuit, the material saving is perhaps sixty dollars, and against that you have a larger conductor to bend into a box, terminals that must be rated for aluminium, and an extra preparation step. Copper is simply easier at that scale. Aluminium starts winning on long feeders and large conductors, which is where the price gap becomes hundreds or thousands of dollars.

What does AL-CU or CO/ALR mean on a terminal?

They are markings that indicate what conductor material a termination is listed for. AL-CU appears on lugs and breakers rated for both aluminium and copper, and CO/ALR appears on devices such as receptacles and switches rated for aluminium branch circuit conductors. An unmarked terminal, or one marked CU only, is listed for copper alone, and connecting aluminium to it is a defect regardless of how tight it feels.

Does aluminium wire have more voltage drop?

For the same conductor size, yes, because aluminium has higher resistance per foot. For the same ampacity it is close, because the aluminium conductor is one or two sizes larger. On a long run, voltage drop rather than ampacity often picks the size in both materials, and once you are sizing for drop, the aluminium option gets larger and still usually costs less.

Getting your own panel and load numbers ready for an electrician? The EV Home Charging Install Planner is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.