Copper vs Aluminum Wiring: Weight, Conductivity, and Cost

I was standing in the electrical aisle doing math on my phone

I was in the big-box store, staring at spools of wire like they were going to blink first, and I’m thumbing my calculator because the numbers weren’t lining up. The copper roll felt like a boat anchor, the aluminum felt… weirdly light, and the price tags were doing that thing where you squint and think, “Am I missing something, or is this actually what it costs now?”

So yeah, if you’ve ever tried to compare copper vs aluminum wiring and ended up with a pile of half-notes and a headache, you’re not alone.

And the thing is, people argue about this like it’s religion.

It’s not.

What you’re actually comparing (it’s not just price)

You’re comparing three things that tug against each other: weight, conductivity (how well it carries current), and cost. And then there’s the fourth thing nobody wants to talk about until it bites them: terminations, connectors, and install habits. Because a wire isn’t “good” or “bad” in a vacuum — it’s good or bad in a real wall, on a real job, with real hands tightening lugs.

So if you’re doing a takeoff for a small addition, or you’re roughing in a detached garage, or you’re swapping a feeder to a subpanel, you’ll feel these tradeoffs fast. Copper is smaller for the same ampacity, it’s more forgiving at connections, and it’s heavier. Aluminum is lighter and usually cheaper per foot, but it wants a little more respect: larger size for the same job, correct lugs, proper torque, and the right anti-oxidant paste (not optional, even if someone on a forum says it is).

But why does everyone get this wrong? Because they compare the sticker price of one spool to the other and stop there, like that’s the whole story.

Is that 1.6 number perfect? No. It’s a field shortcut. It gets you in the ballpark fast, and then you still check your code tables, insulation rating, temperature, conduit fill, and voltage drop like an adult.

So if you were thinking “I’ll just swap copper for aluminum, same gauge,” don’t. That’s how you end up with hot conductors and nuisance problems (or worse).

Quick comparison table (the stuff you actually care about)

That “physical size” row is the sneaky one. You can save on wire and then get punched in the face by conduit fill or box fill. I’ve watched guys fight a pull for an hour because they didn’t want to upsize the conduit 1 step.

Weight: why aluminum feels like cheating (until you’re landing it)

I’ll give aluminum this: if you’re pulling a feeder across a long run — say, 120 feet from a meter/main to a shop subpanel — the weight difference is not some nerd detail. It’s your shoulders. It’s whether you need one person or two. It’s whether you’re dragging a spool across gravel and swearing the whole way.

And if you’re doing service entrance cable or big SER runs in a framed wall, lighter cable is just easier to wrestle. It bends a little different, kind of springy, and you can’t treat it like copper because it’ll fight you at the panel if you don’t plan your landing.

So here’s the practical bit: aluminum is nicer to move, but it’s bulkier. That bulk means larger radius bends and sometimes a bigger panel gutter feels “full” faster. If you’ve ever tried to dress conductors neatly and you’re running out of room, you know what I mean.

And yes, that also affects labor. Not always a ton, but enough that you notice when you’re doing a bunch of them.

So weight isn’t just shipping weight. It’s install weight.

Conductivity and voltage drop: the part people pretend doesn’t matter

Okay, this is the long section because it’s the one that actually decides whether your install behaves. Conductivity is basically how easily electrons move through the metal. Copper is better at it than aluminum, so copper can be smaller for the same job. Aluminum can absolutely do the job — utilities use aluminum all the time — but you’ve got to size it correctly and think about voltage drop on longer runs.

Here’s a scenario that’s real enough: you’re feeding a detached garage, you’ve got a small subpanel, and you’re planning for a future welder or a mini-split. You might be in the 60–100 amp range. If you choose aluminum, your conductor gets larger, and now your conduit might need to jump a size. If you don’t jump the conduit, your pull gets ugly, your insulation gets scraped, and now you’ve invented problems.

And voltage drop — yeah, I know, people roll their eyes — but on long runs it’s not theoretical. Lights dim, motors run hot, compressors get cranky. So you size for it. You can use a calculator to sanity-check the math before you buy wire you can’t return because you nicked it.

If you want to do quick checks while you’re planning, I keep these bookmarked:

And yeah, those aren’t wire calculators specifically, but they’re the same idea: don’t guess when you can check yourself in 20 seconds.

Now, about the terminations. Aluminum expands and contracts more with heat cycles than copper does (and that’s where a lot of the old horror stories come from). Modern aluminum alloys and proper rated devices are way better than the sketchy stuff people remember from decades ago, but you still can’t get lazy. You land it with the right lug, you torque it to spec, and you re-check if the manufacturer calls for it. I used to nod when people said “torque matters.” I didn’t really get it. Then I saw a cooked lug that was “tight enough” until it wasn’t.

So: aluminum is fine, but it’s not forgiving. Copper is expensive, but it’s chill.

Cost: the number you see vs the number you end up living with

The material price per foot is what everyone talks about, because it’s easy. But the installed cost is where it gets real. If aluminum saves you a chunk on wire but forces you into bigger conduit, bigger fittings, different lugs, anti-oxidant compound, and a little extra time dressing the panel… you need to count that stuff too.

And if you’re a homeowner doing your first serious electrical project (or you’re helping a buddy, which is how these things always start), the “cost” also includes your risk. Copper gives you more margin for error. Aluminum demands you follow the rules like you actually mean it.

One more thing: if you’re tying into existing copper, you can’t just twist copper and aluminum together and call it a day. You need the right rated connector. Dissimilar metals are a whole thing (galvanic corrosion is not a myth), and the fix is simple: use listed connectors and follow the instructions. That’s it.

FAQ (the stuff I get asked on site)

And if you take nothing else from this: don’t compare copper and aluminum by “same gauge.” Compare them by what they can safely carry, how far you’re running them, and how you’re actually going to terminate them (in a real panel, with real space constraints). That’s the whole game.