If you are choosing between copper and aluminum for an electrical conductor and only remember one thing, make it this: aluminum conducts about 61% as well as copper by volume, but a conductor is bought by weight and price, not by volume — which is why aluminum wins on every utility and busbar job where weight or cost matters more than the last few millimetres of width.
The two metals sit on opposite sides of the same trade-off. Copper is the better conductor per unit of cross-section; aluminum is the better conductor per unit of weight and per unit of cost. Most of the practical decisions in cabling, busbar and connector design come down to which of those two currencies you are actually spending.
The numbers that decide the choice
| Property | Copper (C11000) | Aluminum (1350) |
|---|---|---|
| Conductivity, % IACS | 101 | 61 |
| Resistivity, nΩ·m | 16.8 | 26.5 |
| Density, g/cm³ | 8.96 | 2.70 |
| Conductivity per unit weight | 1.00 (base) | 1.60 × copper |
| Melting point | 1,085 °C | 660 °C |
| Tensile (annealed) | 220 MPa | 85–120 MPa |
The 61% figure is what people quote, and it is true — but it is conductivity by volume. The moment you hold cross-section equal, copper wins on raw current-carrying. The moment you hold weight equal, aluminum wins, because it is a third of the density and over 60% as conductive. That is the entire reason aluminum replaced copper in overhead transmission lines decades ago and stays there.
For a busbar, the arithmetic is even simpler: an aluminum busbar sized to carry the same current as a copper one ends up roughly 1.5–1.6 times the cross-section, but still half the weight and a fraction of the material cost. If the enclosure has room for the extra section, aluminum wins on price; if the spec has a fixed footprint and no room to grow, copper wins because it fits in less space.
Where each one actually wins
- Copper wins on fixed-footprint switchgear, high-vibration connector systems, and anywhere the connection is made by a screw terminal that was never designed for aluminum's larger cross-section.
- Aluminum wins on long cable runs, overhead lines, busbar trunks with room to spare, and any application where weight is a design input — which is most of transportation and every rooftop run.
- The failure mode is almost always the connection, not the conductor. Aluminum forms an oxide instantly and that oxide is a poor conductor; copper does not have this problem to the same degree. That is why aluminum terminations need joint compound and a properly torqued bolted connection, and why the standard says to break the oxide at the joint.
The common mistake
Buying aluminum where a copper-only drawing is in force, or the reverse. A drawing that says "busbar, copper" is usually a copper decision the design has already made — the cross-section, the temperature rise, and the terminal ratings are all built around copper's numbers. Substituting aluminum to save money without re-running the ampacity and the connection design is how a cheap bid becomes a hot joint.
The way to keep it clean is to name the conductor material, the ampacity, the environment and the standard — and let the numbers decide. State the current, the allowed temperature rise, and whether the footprint or the weight is the binding constraint. The metal choice follows from those three, not the other way around.
Supplying stainless steel and aluminum, not copper. At Hongming Metal, copper is a reference line we write about, not a product range we sell. If the deciding factor on your project is corrosion resistance or structural weight rather than conductivity, the ranges we actually ship — stainless steel tube and fittings, and aluminum sheet and plate — are the place to look. Start with the stainless steel tube and pipe range, or the aluminum sheet and plate range.