Aluminum Vs. Copper

Considering aluminum wiring for your PV installation?  It is widely known that the cost of copper is much greater than that of aluminum.  It may seem like an easy choice given that fact alone.  Let’s consider some of the advantages and disadvantages of each.  Some of these factors may help you decide whether or not the two are right for the job.
 

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Advantages of aluminum wiring:

Aluminum is considerably less expensive than copper.  This makes it more desirable to use, especially in large projects requiring extensive wiring and when runs span long distances.  The cost of copper in these types of installs can easily outweigh the cost of using aluminum.

Aluminum is a lightweight material and very flexible, making it easier to work with. This characteristic may lend to faster installs with wire pulls being much quicker in long runs.  However, aluminum does come with some notable disadvantages which should be considered.

Disadvantages of aluminum wiring:

Aluminum conductors are going to be larger than that of a comparable copper conductor.  This requires having larger raceways and added cost.  In some systems this could prove to be a disadvantage over copper.

Aluminum wiring raises potential risk for house fires if not installed with great care and diligence. Expansion and contraction cycles in aluminum have greater impact compared to use of copper.  Overtime these cycles can loosen connections.  If normal inspections of these connections are not performed and loose connections are not tightened there is an increased risk of fire from arching. 

Aluminum is susceptible to oxidation. This occurs when it comes into contact with moisture and dissimilar metals. The oxidization increases resistance in this connection. With too much built up resistance the wire can heat up possibly melt surrounding insulation which could trigger a fire. 

This is combated with anit-oxidation compound at each terminal point.

Aluminum wires require higher maintenance than copper wiring. This includes inspection of the conductors for tight connections and presence of oxidation. 

Advantages of copper wiring:

Copper has greater conductivity compared to aluminum, which leads to smaller (diameter) conductors being required for use.  Having smaller conductors makes installation easier where multiple conductors share the same raceway.  The raceways may also be smaller compared to those needed for aluminum conductors of the same ampacity. 

Copper does not go through major cycles of expansion and contraction as compared to aluminum. The tensile strength of copper allows it to bear the stresses of wear and tear over time without the same effects as aluminum.  Thus it’s a much more stable material choice. Due to its high ductile properties, copper can be formed into very fine wire. This adds to the versatility of copper wire. Copper has a high tensile strength. It can undergo extreme stress but show minimal signs of wear and tear. It is virtually maintenance free.  That is not to say it does not come at a cost….

Disadvantages of copper wiring:

Copper is much more expensive than aluminum. When an elaborate amount of wiring is required for a job, the overall costs of using copper may prove to be prohibitive. It is also much heavier than its aluminum counterpart which can add to the complexity of the installation. Copper wiring requires a bit more support over long distances to keep in place. This could also add up in cost in larger installs.

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It may not be clear cut whether to use aluminum over copper in every situation.  Each project is a little different.  Careful consideration must be made when weighing your options.  Cost of material, installation time, safety and overall maintenance must all be considered when determining which conductor is right for the job.

For our most current analysis of copper price trends, check out this blog post, updated regularly.

One of the recurring questions received by Gordian’s engineers revolves around the question of material impact on estimates. If prices on a type of material are surging, what are the tradeoffs of selecting another comparable option? Questions like these are becoming increasingly common as squeezed supply chain and wild material cost fluctuations have unsettled the construction market and made value engineering an imperative to make the most of project budgets.

For a practical example of the tradeoffs estimators and other considerations preconstruction professionals are making as they plan and design projects, look no further than the choice being made every day: copper versus aluminum wire.

From January 2021 to January 2022, the price of ½” copper tubing increased over 50%, while the average price of electric copper wire has grown over 120% in the same time frame. Many electrical engineers faced with these cost surges for copper materials are turning to aluminum as a substitute.

To help estimators and other construction professionals answer this question, we’ve turned to the industry expertise of Antonio D’Aulerio, Engineer on the Data Team, responsible for managing the electrical divisions for Gordian’s RSMeans data. Antonio discusses the trade-offs for copper and aluminum materials and how to incorporate these decisions when using RSMeans Data Online.

Copper vs. Aluminum Wire

The main criteria for the use of aluminum cable vs copper cables are the cost savings. In buildings, aluminum and copper cables can be used interchangeably for power in low voltage installations. For communications and control, copper is more commonly used. In fact, nearly all electronic cables are made from copper.

The main difference between aluminum and copper cables is the current carrying capacity and resistance. Aluminum cable has a lower current carrying capacity (by about 40%) and greater resistance (requiring 50% larger cross-sectional area on average) than the equivalent copper conductor. As a rule of thumb, using aluminum conductors two American Wire Gage sizes larger than copper are typically sufficient for replacement. Aluminum will take more space to carry the same amperage as copper, meaning it will need a bigger raceway or enclosed channel designed for holding wires, cables or bus bars with additional functions.

The drawbacks for using aluminum:

• It’s less flexible and more labor intensive. Aluminum is more difficult to work with, so the cost of termination is higher.
• It needs a special compound at termination (or the lug must be a special Al-Cu type) to avoid galvanic corrosion. This can be a serious risk factor in damp conditions.
• For long runs, aluminum has more voltage drop so engineers may need to upsize the cable to compensate.
• Aluminum cable is prone to cracking and failure when subjected to vibration. This may be a greater consideration for industrial building projects where installed machinery produces high quantities of low and high frequency vibration.

Copper Versus Aluminum Wire: Using RSMeans Data Online to Estimate the Difference

The example below uses RSMeans Data Online to compare a 200A service entrance. The first one uses copper cable 3/0 and a 1-1/2” conduit. The second one uses aluminum cable 250 MCM and 2” conduit. The aluminum option is slightly cheaper overall, even though the cost of the wire went down 48% from $423 to $219 and the raceway components went up in price by 23%.

Option 1: Copper Cable

Option 2: Aluminum Cable

RSMeans Data Online is a powerful tool that allows you to compare options and make data-driven value engineering decisions to better support your projects. Want to try this out for yourself with different estimates and location factors, or trend this over time with the Historical Cost Index? Follow the links below to learn more about how to use these tools for your estimates, or sign up for one of Gordian’s training sessions to get hands-on guidance.

• Already have an account? Use one of our Product Guides.
• Use the Historical Cost Index to move your estimates over time.
• Use the City Cost Index to localize your estimates.
• Sign up for in-depth RSMeans Training.

Get Started Today

Ready to explore cloud-based construction cost estimating with RSMeans Data Online?

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