Wires are an important element in the bigger picture of the entire circuitry. As they are the sole medium that carries electricity, their characteristics greatly affect the entire electrical system.

Therefore, if you wish to install a subpanel, you need to use appropriate size wires. But what size aluminum wire for 100 amp sub panel?

The short answer is #2 AWG for aluminum wiring and #4 for copper wires. But the answer can vary based on the length of the cable you are choosing to install.

In this article, I will be discussing in detail the importance of wire gauge, wire material, and wire length. I will also talk about how these factors can affect your circuitry and sub panel. So without further ado, let’s begin.

What Size Aluminum Wire For 100 Amp Sub Panel

Why is AWG and Why Is It So Important?

AWG is an acronym for American Wire Gauge. According to American standards, wires are classed based on their current capacity and length. The electrical capacity is determined by the thickness of the copper/aluminum wire used.

There are numerous gauge values for cables. The current capacity and the gauge number have an inverse relationship. Because a 6 AWG wire is thicker than an 8 AWG wire, it has more capacity and efficiency.

Fig 1- AWG Wire Gauge Calculator
Fig 1- AWG Wire Gauge Calculator

In the above diagram (Fig 1), we can see a calculator for the wire gauges in AWG. We can see that #0 is the thickest gauge and #36 is the thinnest gauge on the calculator.

The more amps you need to transfer; the bigger gauge you will require. The same goes for distance. If you intend to transfer electricity over a greater distance, you need a thicker wire. For example, what size wire is needed to run a 500 feet power supply? Since the distance is very long, you would need a very thick wire.

Using a thinner wire than the recommended gauge is highly advised against. It could result in the wire melting down and even in some worst cases, fire hazards.

What Gauge Wire Should You Use for a Sub Panel?

The answer will vary based on the amperage, material, and length of the cable. But for a 100-amp subpanel, #2 AWG aluminum wires are required. Let’s take a look at the chart below which goes deeper into the gauge requirements.

Amperage Ratings VS Aluminum Wire Gauge Chart (in AWG)

CurrentAluminum Wire
20 amps12 AWG
30 amps10 AWG
40 amps8 AWG
50 amps6 AWG
100 amps2 AWG

As can be seen from the above panel, as the amperage increases, so does the thickness of the aluminum wire. Which means a smaller gauge.

Now for our main query, what size aluminum wire for 100 amp sub panel? The appropriate wire gauge for a sub panel dealing with 100-amps is #2 AWG for aluminum cables. However, if you wanted to transfer 50-amps at 150 feet, a thinner wire would suffice.

Using a #2 AWG aluminum wire will ensure the proper flow of electricity from the main panel to the sub panel. Given that the sub panel is not very distant from the main panel, it will not generate much heat. As well as be safe from any significant voltage drops.

Aluminum is also lighter than copper. 70% lighter to be exact. But it is also less conductive than copper. It is only 61% as conductive as copper. But over short distances and high amperages, it should not matter much.

How Does the Wire Gauge and Length Affect the Circuit?

There are several factors that can be affected by the gauge of the wire and its length. Such as voltage drops, heat generation, etc.

I will discuss some of the effects of wire gauge and length on the circuit below:

Heat Generation

When current flows through a conductor, heat energy is generated in the conductor. This heat generation is dependent on a few factors. Especially resistance. More resistance means more heat.

Voltage Drops

The longer the wire, the more voltage drop the circuit will face. As electricity has to travel a longer distance, it gets weaker with time.

Thus voltage drops occur. Also the material matters as well. Copper is way more conductive than aluminum. Thus copper will face fewer voltage drops than aluminum.

Line Loss

The line loss in a wire is determined by the wire length, diameter, and current flowing through it. Larger wires offer lower resistance and can carry more power with fewer losses.

If the quantity of power carried is minimal or the wire is not very long, losses in smaller wires remain low.

Wire Resistance

The longer a wire, the more resistant it becomes. This means that it becomes harder for electricity to pass through it. Which in turn increases heat.

On the other hand, a shorted wire means less resistance is provided by the wire. This minimizes the heat which is generated.

Performance of Inductance Loops

The reality is that wire gauge has an impact on inductance loop performance, which has been extensively proven in the traffic business.

When comparing huge loops or loops with extended lead-in lengths, the difference in performance is immediately visible.


Oftentimes an overlooked sector. The thicker and longer the wire, the more it will cost. As the mass of the conductive metal is increased with its diameter and length.

Aluminum wires tend to cost way less than copper. Almost as half as copper wires.

These are some of the common factors which can be affected by your choice of wire gauge, material, and length.


I have answered what size aluminum wire for 100 amp sub panel would be perfect to use. If you wish to install a sub panel with an amperage rating of 100 amps or so, you may use a #2 AWG aluminum wire for it.

However, electricity is a very dangerous and fragile subject. So it is highly advised to consult with a professional before you make such a serious decision. As there could be several factors involved with the installation procedure. As each household has different settings and different factors in the equations.

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