Why are US Homes Wired Using Solid Wire rather than Stranded Wire?

Electrical Technology

Why Do the Electricians in the U.S.A opt-out for Solid Wire Instead of Stranded Wire While Doing Home Wiring?

In most countries across the EU, UK, South America, Africa, and Asia, electricians and homeowners prefer stranded wire instead of solid Wire for home wiring. This is mainly due to its flexibility, ease of routing, and durability.

However, the situation is different in North America, particularly in the United States (U.S.), where solid wire is commonly used for residential wiring. It is widely used in 15A and 20A circuits for 120V and 240V supply voltages.

Now, why is solid wire preferred in the U.S.? One key reason is that solid conductor of the same gauge as stranded wire can carry more power at a frequency of 60Hz.

Let’s explore other reasons as well:

Related Post: Stranded Wire vs Solid Wire. Which One is Best and Why?

Why is Solid wire used in the U.S for home wiring while stranded wire is used in the rest of the world?

As we all know that one of the main advantages of stranded wire over solid wire is its flexibility, but the homeowners and electricians use solid conductors in home applications for single phase circuits due to the following reasons.

Solid wire is cheaper as compared to stranded wire due to its complex process of production.
Solid conductors carry more power than stranded wire if the diameter of both wires are the same. In other words, for the same size, the ampacity or current carrying capacity of solid wire is more than the stranded wire.
For the same wire gauge size (say #6 or #10 AWG), the cross sectional area of stranded wire is larger than the solid wire. This is due to the air-gap between the strands in it and it make a noticeable difference. Especially, when multiple wires in the electrical box or any other specific area are used.
As mentioned earlier, the key advantage of stranded wire is its flexibility, making it easy to route and bend smoothly. However, in the case of solid wire, the wiring is typically installed permanently behind walls, ceilings, and floors. Since the wires remain fixed in place, the flexibility of stranded wire is not a significant advantage in home wiring. Therefore, using solid wire instead of stranded wire makes little difference in such installations.
The termination and connections of breakers, switches, outlets etc. are perfect in case of solid wire while there may be complexity while connecting the stranded wires as there may be individual strands out of the screw terminals and loose connection when fold back the wires into/out of the box.
In the case of solid wire, It is easy to splice together with a wire-nut. In addition, the solid wire won’t damage or wear/tear if you pull out tightly back to check the connection. And yes, life gets easy when you undo the wire nut connection for solid wire while in case of stranded wire, the strands of conductor may break when you undo a joint or open a wire nut.
The skin effect in solid wire may be neglected in case of home wiring because the skin depth is 8.5mm (1/3″) in case of copper for 60hz of supply frequency. This way, it wont play a role if the diameter of the wire is more than 17mm (2/3″). In short, you may use stranded wire up to 6mm (10AWG) for enough flex if needed, other than solid conductor is perfect.
Solid wire is less likely to be affected by corrosion and vibration due to the less surface areas as compared to the stranded wire especially when used for outdoor applications.

These all are the specific reasons why electricians in the USA use a solid wire for basic circuits for home wiring instead of a stranded wire. If you (Master Electrician) know something other than the above reason, please share with us in the following comment box.