Wondering about the right wire size for your 100 amp service? We’ve got you covered.
For a 100 AMP service, the recommended wire sizes are 4 AWG or 2 AWG for copper wiring and 2 AWG, 1 AWG, or 1/0 AWG for aluminum or copper-clad wiring. If the distance is more than 50 feet, it’s advisable to use #2 AWG copper wire. For underground service, you can install the wire inside a 1.25-inch PVC conduit, either Sch 40 or Sch 80.
Selecting the appropriate wire size can be confusing, especially for beginners. In this guide, we’ll provide clarity by answering all your questions and addressing any doubts regarding wire size for a 100 amp service.
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This post includes some affiliate links.Where is a 100 amp service used?
You can install a 100 amp service in commercial applications, like large office buildings with multiple air conditioners or in server rooms with many computers.
You can use the service for areas with multiple heating appliances, like Fire Stations.
Even small residential locations are ideal, like houses where people use electrical appliances to speed up their lives.
However, some people do not use the 100 amp service because they want to avoid bearing the installation and upgrade costs of their home service.
What size of wire should I use for 100 amp service?
The best gauge wire for a 100 amp service should be #2 AWG.
You will need to use the wire from the breaker panel if the electrical load is quite a long distance.
A copper wire with 2 AWG would be a good choice.
But, the size changes depending on factors like wire material, distance, voltage drop, phases, etc.
Wire material
The wire size is different for 100 amp if you use wires with different materials.
You must have a #4 AWG wire if you use copper wires.
If you use aluminum or copper-clad aluminum wires, you need a #2 AWG wire.
While deciding the wire size, you must limit the voltage drop to 3%.
Distance
The distance will decide the wire size of the 100 amp service.
You should know the length of your service line from the meter to the electrical service panel before you decide on the wire size.
The maximum voltage drop to be used while deciding the wire size is only 3%.
The wire material will also determine the wire size for the estimated distance between the meter base and the electrical panel.
Here are some wire sizes with distance:
- For 50 feet distance or less, use a #2/0 copper wire or #4/0 aluminum wire.
- For 100 feet or less, use a #3/0 copper wire.
- For 150 feet or less, use a #4/0 copper.
- Run only a kcmil wire for 100 feet or less.
If you want to run wires for 100 amp service 150 feet distance, you should get:
- 2/0 AWG copper wire or 4/0 AWG aluminum or copper-clad aluminum wire for single-phase circuits.
- 1/0 AWG copper wire or 3/0 AWG aluminum or copper-clad wire for 3-phase circuits.
If you want to run wires for 100 amp service 300 feet away, use:
- 4 AWG copper wires, 250 kcmil in diameter
- 2 AWG aluminum or copper-clad aluminum
For running wires in 100 amp service 200 feet away, the wire size will be the same, i.e., 2 AWG copper or 4 AWG aluminum, or copper-clad aluminum.
However, if you install a 50 amp appliance in a 100 amp service 200 feet away, you need a 0 AWG wire.
As you can see, the wire size for 100 amps changes along with the distance.
Sometimes, it doesn’t change.
Voltage drop
Voltage drop refers to voltage loss because of the resistance when the current flows through the wires to appliances.
For example, if the voltage drop is 3%, in a circuit of 120 volts, the voltage should stay within 117 volts.
In a circuit with 240 volts, the voltage should be up to 233v.
The standard voltage drop is considered to be 3%.
But, it can also drop to 5%, but that’s the maximum.
The wire size will vary depending on the voltage drop.
The wire gauge should be thick and superior if the voltage drop is high.
If the wire diameter is thin, it won’t be able to carry the voltage drop.
Source voltage
If you have increased the electric circuit in your house, you should consider the source voltage.
The source voltage can differ from place to place.
Generally, 120 volts is the standard source voltage in the United States.
However, some industries may have a different voltage.
Phases
The term may sound doubtful, but it is easy to understand.
The number of phases refers to the load distribution.
There are two common phases – single phase and 3-phase.
A single phase needs 3 wires, but a 3-phase requires 4, one being the ground wire.
The single-phase circuits are used in houses, and 3-phases are used in industries as they carry higher loads better.
Ground wire size
The wire sizes for grounding are slightly different from those used for hot and neutral lines.
This is because the ground wires only carry current when there is a short circuit.
In that case, there might not be an issue if the wire size is slightly inferior.
However, the wire size must be able to carry enough current during a short circuit without overheating.
The minimum ground wire size for a 100 amp service should be:
- #8 AWG copper wire
- #6 AWG aluminum or copper-clad aluminum wire.
Why is the wire size different for copper and aluminum?
In electrical works, contractors generally use three types of wires:
- Copper
- Aluminum
- Copper-clad aluminum
You might have seen that the copper and aluminum or copper-clad sizes are slightly different.
But why the difference?
Let’s figure it out.
Copper wires
Copper wires are the most famous and best wire materials used for electrical purposes.
Copper is better in many ways.
It is highly conductive, strong, and durable.
Below are some advantages of copper wires:
Conductivity
Copper wires have higher conductivity than aluminum or copper-clad wires.
Copper wires can carry more currents than aluminum without overheating the wires.
That is why these wires are ideal for longer distances.
Heat resistant
Copper wires do not heat up easily despite being able to carry loads of current.
The wires are extremely resistant to heat compared to aluminum wires.
Besides, the wires do not contract or expand, so the current flow is smooth and flexible.
There is no interruption in the current flow; thus, the wires do not become hot.
Corrosion resistant
Copper wires have a green tarnish layer called Patina, which gets oxidized due to exposure to open areas.
This layer protects the copper wires from corrosion.
However, the layer does not affect the wires or stop them from working.
Malleability
Copper wires are very malleable.
You can work with them by bending or folding without worrying about any risks of breakage.
So, if you opt for copper wires for 100 amp service, it should be a 4 AWG wire.
Aluminum wires
Aluminum wires are good wires, but copper is better.
Aluminum does not have high conductivity like copper wires.
So, they heat up easily and cannot be used for longer distances.
The longer the wire, the higher the resistance and the chances of overheating.
Besides, the wires contract and expand too much, so the current flow gets interrupted multiple times.
Since the wires are weaker than copper, there could be chances of breakage.
But you can still use aluminum wires with little adjustments.
You can use higher gauges to replicate the copper wires.
For example, if 100 amp requires 4 AWG copper, opt for 2 AWG aluminum wires.
Despite these disadvantages, aluminum has two good merits:
Cost
Aluminum wires are cheaper than copper wires.
They are not as good as copper, but you can still use them carefully.
Lightweight
Aluminum wires are very light to handle.
As a result, installing and fixing the wires is easy and fast.
So, if you want aluminum wires, choose the 2 AWG wires.
Copper-clad aluminum
This wire is a better version of aluminum.
The wires are more conductive and durable than pure aluminum, but pure copper is better.
The wire has some copper fittings at the wire ends, giving a few copper benefits.
The wire is cheaper than copper but more expensive than pure aluminum.
You can try these wires if copper seems very costly.
The wire size will be 2 AWG.
What size of wire do you require for a 100 amp sub-panel?
Depending on the wire type, the wire size will change for a 100 amp sub-panel.
In general, a 100 amp sub panel needs #4 copper and #2 aluminum wires.
Here is detailed information about the wire sizes and types.
| Copper wires | Aluminum wires |
|---|---|
| #3 THHN/THWN-2 Wire | #2 XHHW-2 Wire |
| #2 THHN/THWN-2 Wire | #1 XHHW-2 Wire |
| #2/3C with ground tray cable (THHN-PVC) | 2-2-2 Ramapo Triplex Underground SEcondary Distribution Cable is a #2 gauge wire. Compared to other wires, you do not have to bury them in the conduit. It is rated for direct burial. |
What is the conduit size for 100 amp service?
Generally, 1.25 inches of conduit would be fine for a 100 amp service.
You can try the PVC-Sch 40 or 80 gray electric conduit for the conduit type.
It is not a mandatory size.
You can also increase the conduit size to around 40% or less inner fill.
A 1.5 or 2-inch conduit would be the best for 100 amp service.
You can run 3 or more electrical wires in the same tube.
In NEC 2020, Chapter 9 Table 5A, a 2 AWG stranded aluminum wire can take up to 112.9mm² of fill space in the conduit.
So, if you use three wires bearing the same size, the fill would be 338.7mm².
According to Chapter 9, Table 4, if you use a 1.5-inch PVC-Sch 80 conduit, you will receive at least 442mm² space.
You must ensure that the space of the cables doesn’t exceed 40% of the conduit’s volume.
The conduit has to be buried 24 inches deep in maximum areas.
Choose a conduit that can handle more.
PVC Schedule 80 is thicker and stronger than Schedule 40.
However, the outer diameter is the same in both.
What is the wire size of a 100 amp breaker?
A 100 amp breaker is quite a big circuit breaker.
You will require at least 1 AWG wire to install wires in this breaker.
Depending on the wire material, you should use 3 AWG copper or 1 AWG aluminum or copper-clad aluminum wires for a 100 amp branch circuit.
Do not mistake using smaller gauges like 4 AWG copper or 2 AWG aluminum.
That will fry the breakers and subpanels.
A table on wire sizes for 100 amp
This chart will help you determine the wire sizes for 100 amp depending on the voltage, phase, and wire material.
Single phase
120-volt wire size
| Distance | Copper wire | Aluminum wire |
|---|---|---|
| 50 ft | 1 AWG | 1/0 AWG |
| 75 ft | 1 AWG | 1/0 AWG |
| 100 ft | 1 AWG | 1/0 AWG |
| 200 ft | 2/0 AWG | 4/0 AWG |
| 250 ft | 3/0 AWG | 250 MCM |
| 300 ft | 4/0 AWG | 300 MCM |
240-volt wire size
| Distance | Copper wire | Aluminum wire |
|---|---|---|
| 50 ft | 1 AWG | 1/0 AWG |
| 75 ft | 1 AWG | 1/0 AWG |
| 100 ft | 1 AWG | 1/0 AWG |
| 200 ft | 1 AWG | 1/0 AWG |
| 250 ft | 1 AWG | 2/0 AWG |
| 300 ft | 1/0 AWG | 3/0 AWG |
480-volt wire size
| Distance | Copper wire | Aluminum wire |
|---|---|---|
| 50 ft | 1 AWG | 1/0 AWG |
| 75 ft | 1 AWG | 1/0 AWG |
| 100 ft | 1 AWG | 1/0 AWG |
| 200 ft | 1 AWG | 1/0 AWG |
| 250 ft | 1 AWG | 1/0 AWG |
| 300 ft | 1 AWG | 1/0 AWG |
3-phase
120-volt wire size
| Distance | Copper wire | Aluminum wire |
|---|---|---|
| 50 ft | 1 AWG | 1/0 AWG |
| 75 ft | 1 AWG | 1/0 AWG |
| 100 ft | 1 AWG | 1/0 AWG |
| 200 ft | 2/0 AWG | 3/0 AWG |
| 250 ft | 3/0 AWG | 4/0 AWG |
| 300 ft | 3/0 AWG | 300 MCM |
240-volt wire size
| Distance | Copper wire | Aluminum wire |
|---|---|---|
| 50 ft | 1 AWG | 1/0 AWG |
| 75 ft | 1 AWG | 1/0 AWG |
| 100 ft | 1 AWG | 1/0 AWG |
| 200 ft | 1 AWG | 1/0 AWG |
| 250 ft | 1 AWG | 1/0 AWG |
| 300 ft | 1 AWG | 2/0 AWG |
480-volt wire size
| Distance | Copper wire | Aluminum wire |
|---|---|---|
| 50 ft | 1 AWG | 1/0 AWG |
| 75 ft | 1 AWG | 1/0 AWG |
| 100 ft | 1 AWG | 1/0 AWG |
| 200 ft | 1 AWG | 1/0 AWG |
| 250 ft | 1 AWG | 1/0 AWG |
| 300 ft | 1 AWG | 1/0 AWG |
Note: The voltage drop here is considered as 3%.
Some good 100 amp wires and circuits
If you are looking for recommendations, here are some:
Wires
- 2 gauge 2 AWG 20 feet Black + 20 Feet red
- EWCS 2 AWG UL Approved Marine Grade Tinned Copper Wire
Circuit breaker
- Q2100 100-Amp Double Pole Type QP circuit Breaker
- Siemens PN2020B1100C PN Series 100 amp Space 20-circuit main breaker box
Final thoughts
The best wire size for 100 amp service is a 4 AWG copper wire or a 2 AWG aluminum or copper-clad aluminum wire.
Copper wires are better because they have high conductivity, malleability, and durability. They can carry loads of electricity without overheating and can be used for longer distances.
Aluminum and copper-clad aluminum are inferior but still usable. Both are cheaper and lightweight. However, copper-clad can give some copper benefits and, thus, are more expensive than pure aluminum.
The wire size changes depending on various factors. The ground wire size is 8 AWG copper wire or 6 AWG aluminum wire.
The table given should help you determine the wire sizes depending on voltage, distance, and phase.
Related Articles:
- What Size Wire Do I Need For 125 AMP Service?
- What Size Wire Do I Use For 150 AMP Service?
- Size Of Ground Wire For 200 Amp Service: Complete Guide With Table
FAQs
What will be the installation charge for the 100 amp service?
Installing a 100 amp service will require three elements 100 amp feeder wire, a conduit, and a 100 amp sub panel.
Consider the additional service charges, the distance, and the installation area.
The complete cost would be around $1,500-$4,500, the average being $3,000.
The average cost for a 100 amp electric panel will be $500-$1,500, with a median price of $1,00.
For a 100 amp feeder wire, the average price would be $1,000-$3,000, with a median price of $2,000.
How many wires can you run in a 100 amp service?
The 3-wire cable from the meter to the main box will contain 2 hot wires and one neutral wire.
The feeder cable is a 4-wire that contains 2 hot feeder wires, one neutral wire, and one ground wire.
Data Source: National Electrical Code, NEC Wire Table, Electrical wiring, Home wiring.
