Is It OK To Splice/Connect Copper and Aluminum Wire Together?

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When it comes down to home wiring, copper and aluminum wires are both popular choices. Traditionally, aluminum wires were used for home wiring. Today, however, copper wiring is becoming more commonly used in home wiring. However, can you splice these different wires together?

The National Electrical Code allows for the splicing of copper and aluminum wire, provided that an AL/CU rated connector is used. When spliced together, these wires are at risk of corrosion when exposed to moisture. An approved connector needs to be used to prevent the risk of a safety hazard caused by connecting these wires. 

Where your home’s wiring is concerned, you always want to ensure that you don’t violate any of the NEC codes set out by the National Fire Protection Association. In the following sections, we’ll break down everything you need to know about splicing copper and aluminum wire together without violating any codes!

Note: Remember that your top priority, particularly when you are working with electrical equipment, has to be safety. While efforts have been made to fact-check this article for accuracy, every electrical installation is different. If you are in any doubt about what electrical work or modifications are required, you should seek advice from a qualified electrician.

An Overview of Copper and Aluminum Wires

Romex wire which is stripped at one end
Romex wire which is stripped at one end

Here’s a brief overview of both copper and aluminum wires!

What is Copper Wire?

Copper wire, which has a reddish color, is one of the best wires for electrical conductivity. For this reason, it’s commonly used in many household cables. From your HVAC system to your HD flat-screen TV, copper wires are used in many household appliances.

Copper is a non-corrosive material, making it the ideal wiring material. However, copper is generally more expensive than other wiring options. It is also heavier than other types of wires. However, copper is a fantastic thermal conductor. Many modern homes are now switching to copper wiring.

What is Aluminum Wire?

Aluminum wires are widely used for cables. Ultimately, the popularity of aluminum cables comes down to their unique properties. Aluminum wires are known for their lightweight nature and recyclable nature. Aluminum is a non-magnetic metal and is one of the best conductors.

Due to these properties, aluminum wires have been commonly used in homes. However, modern homes are now switching to copper wire. That is because the CPSC (the United States Consumer Product Safety Commission) revealed that homes with aluminum wires were more than 50 times likely to be at risk of a fire hazard.

The Differences Between Copper and Aluminum Wires 

Before we take a look at whether or not it’s possible to splice copper and aluminum wires together, let’s take a closer look at these wires and how they differ from each other.

#1: Copper Has Higher Conductivity

The properties of copper and aluminum differ greatly. Due to their varying properties, copper has a higher conductivity than aluminum. In fact, aluminum wiring has 40% less conductivity than copper wiring. This makes copper wire an ideal choice for wiring.

#2: Aluminum Wires Are Lighter

Compared to copper wires, aluminum wires are more lightweight. Due to this, aluminum wires are also cheaper to purchase. Copper wire, on the other hand, is heavier and more expensive. These factors are closely linked to their molecular properties.

#3: Copper Wires Resist Thermal Effects

In high temperatures, aluminum wires have the tendency to expand. In low temperatures, those same aluminum wires will contract. Copper wire, however, is able to resist the effects of temperature changes.

#4: Aluminum Wires Are Corrosive

One of the drawbacks of aluminum wires is their corrosive nature. This is linked to the safety dangers the CPSC discussed regarding aluminum wires and the risk of a fire hazard. Copper wire, however, is non-corrosive. Ultimately, this makes copper wire the safer wiring choice.

Can You Splice/Connect Copper and Aluminum Wire Together?

Various shrink tube connectors and some wire
Various shrink tube connectors and some wire

In the 2020 National Electrical Code, conductors are discussed in Article 110, Requirements for Electrical Installations. In Section 110.5, it is stipulated that conductors that are used in your home to carry current must be made of copper, aluminum, or copper-clad aluminum materials.

From the above, it is clear that you can legally use copper or aluminum wire in your home. As discussed earlier, there are safety benefits to opting for copper wires over aluminum wires. However, can you splice or connect copper wire to aluminum wire together?

Firstly, let’s take a look at whether or not the National Electrical Code allows this. In Section 110.4, Electrical Connections, the NEC discussed splicing or connecting conductors of different metals. In this section, it is stated that differing wires – such as copper and aluminum wires – cannot be spliced where physical contact occurs between them – unless the device is rated for use like that.

Essentially, this means that you can splice or connect copper and aluminum wire together when using the correct device. This means that the wire connector you choose needs to be approved for joining AL/CU.

Warning: Many people would advise against splicing copper and aluminum wires. That is because the combination of these wires is known to corrode quickly when there is any moisture present. Equally you will need to consider any heat built-up from the current flowing through the wires and wire connector. It might not be safe to just think “right, I’ve connected these two cables together – job done“.

For these reasons, many electricians would recommend sticking to one type of wiring in your home and rewiring where necessary.

However, as per the National Electric Code, it is possible to splice these different wires when the device is rated for that usage. Keep reading as we look at tips for connecting copper and aluminum wires!

Tips for Splicing Copper and Aluminum Wire Together

One type of wire nut connector
One type of wire nut connector

As discussed earlier, it is possible to splice aluminum and copper wire together despite their differing properties. When doing this, however, there are a few important considerations to keep in mind. With these tips, you’ll be able to safely splice or connect copper and aluminum wire.

#1: Only Use AL/CU Rated Connectors

When splicing copper and aluminum wire together, you’ll need to use an appropriately rated connector. By doing this, you’ll avoid violating any NEC codes. Luckily, there’s the perfect product for you to use to safely splice these different wires.

When connecting aluminum and copper wire together, you can use IDEAL Twister’s AL/CU connector. This twist-on wire connector is designed to both prevent corrosion between these different wires and ensure a secure connection. This connector complies with NEC Section 110.14, which we discussed earlier. This connector is also UL-listed.

#2: Use The Correct Connector Size

If you decide to use a connector different from the one discussed above, you’ll need to ensure that you use the correct connector size. This will help ensure a secure connection, increasing the safety of your connection between these wires.

#3: Use Corrosion Inhibitor Paste

Earlier, we discussed the nature of copper and aluminum wires to corrode in the presence of one another. The IDEAL Twister connector discussed above prevents this. However, you can take additional precautions by using an antioxidant corrosion-inhibitor paste.

With the use of an antioxidant paste, you’ll be able to further prevent corrosion from occurring between these different wires. Furthermore, this type of paste is safe to be used with the conductive metals and the equipment you use. The instructions provided by the manufacturer should always be followed when applying this paste to copper and aluminum wires during the splicing process.

#4: Ensure Wires Are Secure

When splicing or connecting copper and aluminum wiring, you always want to ensure a tight and secure connection between the wires and your AL/CU-rated connector. When using a connector like the IDEAL Twister, you’ll be able to ensure that you have a secure connection between your wires.


Traditionally, aluminum wires have been used due to their cost-effectiveness and lightweight nature. However, there has recently been a shift towards copper wires due to improved safety aspects. Given that these different wires are both popular wiring materials, the chances are you might need to splice them together at some point.

Luckily, you’ll be able to splice copper and aluminum wires together without violating any electrical codes. To do this, you’ll need to use a connector that is rated for an AL/CU connection, such as the IDEAL Twister connector.

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About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.