How To Wire A 100 Amp Service Panel: Video Tutorial

Most contemporary homes have what is now commonly referred to as an electrical service panel or the service panel. This service panel acts as the first point of contact beyond the main meter where a power disconnect is triggered and also the point where the neutral ground bond occurs.

A 100 amp panel installation is similar to a 200 amp panel, and therefore, the procedure followed during installation is similar. If a 100 amp panel will be a subpanel, the panel will have isolated ground and neutrals with the bonding strap removed. For any electrical works around your home, it is always best to seek the services of an electrician, especially when installing service boards.

In comparison, the only minor difference between a 100 amp and the 200 amp panels could probably be the sizing of the main circuit breakers and the thickness of the wire cables used to connect the meter box to the breaker box.

Installing A 100 Amp Service Panel

To shade a little light into this type of service, a circuit breaker bearing 100 amp is enough to power up a condo or, to be more precise, a two-bedroomed apartment.

For larger households with a breaker box of 200 amps or higher but still require more voltage, a 100 amp panel could also be added as a subpanel.

A 100 amp sub panel installation requires #4 copper wires or an equivalent of #2 aluminum wires. Aluminum is often used for service entry wires because it’s much cheaper than copper, lightweight, and easy to work with despite copper being a better conductor. 

To add a breaker sub panel to a service panel, the electrician should install the 100 amp main breaker across two breaker slots. If there is none available, the electrician should reconfigure certain wires and breakers to provide the extra space. An electrician can accomplish this by adding 2-pole breakers or tandem breakers to allow 2 circuits to share a single breaker slot safely.

His job is to configure then the route to which the cables will take toward the breaker sub-panel. He will also need to strip off the ends of the necessary wires to facilitate a proper and secured connection before connecting the wires to the subpanel terminals and the main breaker, making sure the connection is complete.

Service Panel

When we talk of an electrical service panel, two things come up;

  1. The Main Panel, which is the main disconnect breaker, 100 amps in this case is the Service Panel.
  1. The Distribution Panel is the circuit breaker panel with the entire circuit load that may be inside, possibly in the garage.

In older homes, you are sure to find the main service disconnect and the breaker together. Today, the main disconnect is installed outside and the distribution panel inside.

Often, you will find a single circuit breaker at the meter, which is the service disconnect, and one or more remote distribution boards inside the residence where the other breakers are located.

You are also more likely to find a distribution panel with its disconnect circuit breaker either on the top or bottom, depending on how the electrician installed the panel. It is always good to know that a panel is considered a sub-panel when there is a main disconnect at the meter.

Therefore, a service panel is the distribution point that connects the incoming main service wires (service drop) to the exit wires(branch wire circuits), which branch off to distribute electricity to different parts of the house. 

Note that a circuit breaker panel is not the same as a fuse box because it has mechanical, toggle-switch circuit breakers, not fuses, but it does perform the same function. 

The older fuses pull in and out instead of the rocker-style method of installing and removing circuit breakers.

An electrical service panel composes of the following;

  1. A swinging hinged door providing access to the switches.
  2. Protective cover giving access to the technical part of the panel.
  3. Two cables that receive power coming in from the outside
  4. Extra Circuit Breaker
  5. Open or shut spaces for extra circuit breakers (optional).
  6. Assortment of wires that run from the circuit breakers to the circuits that service areas of the house.

In single-family residences, the building owner owns the electric service panel, not the electric company. Thus, the owner is responsible for all issues related to the electric service panel.

Why Home Inspections Are Important

As a homeowner, understanding the basics of your home’s electrical service panel will keep you safe and your home well-lit and energized.

You will even save money since operating an electrical service panel is crucial to every electrical repair, from replacing an outlet to wiring an entire room for remodeling.

Distribution Panel And Its Dynamics

To successfully wire a 100 amp service panel, it is essential first to understand the wiring technique and the required wire gauge.

Safety is paramount and takes the front seat when doing any electrical work on your home. 

If you should install wires that are too small to safely handle the load on large lines that, for example, carry 100 amps, they will routinely overheat and may start a fire.

Mistakes of this nature could turn deadly, so you must use the correct gauge wire before carrying out any electrical work of this nature.

Sub Panels

100 AMP Wire Size is a three-wire cable consisting of three insulated conductors and a bare copper ground wire. In most homes, you will only see a 100 amp service on secondary service panels, which are often called “sub-panels.”

Many homes also have a master service panel that feeds from the municipal hookups and one or more secondary panels fed by the master panel.


What gauge wire to use majorly depends on the distance the wire is supposed to cover.

Electrical wires have resistance which eats up current. Longer wires have more resistance simply because they are longer and need to draw more power from the source so that enough power to make it to the outlets.

Advice: If you plan to run your cable 20 feet or more, you may want to consider moving up to 1/0 4-wire.

The cable must have a wire gauge sufficient to the amperage of the subpanel. The cable must also have one or two hot wires depending on your needs, one neutral wire, and one ground wire. 

When it comes to a 100 amp line, and you find yourself in the margin between two gauge sizes, err on the side of caution.

This is because if you choose to use a gauge that is too large, you will have spent a little more money than you probably needed to have spent, and if you use one that is too small, the circuits will perform poorly, and you run the severe risk of an electric fire.


When carrying out electrical work, especially on a service panel, always shut off the power higher up the line. You may need to call your power at the hookups. This is an act of caution to ensure proper wiring that will guarantee your household’s safety against any electrical surprises.

After completing any electrical work involving 100 amp lines, always arrange for an inspection by a licensed electrician.

Related Questions

  1. For a 100 amp sub panel, what is the advisable ground wire size to use?

For a 100 amp sub feeder, the associated ground wire needs to be an 8 AWG Copper or 6AWG aluminum wire.

  1. Is it possible to install a 100 amp subpanel on a 100 amp Service Panel? 

Yes, you can safely run a 100 amp sub-panel on a 100 amp main panel because the total could be up to twice the amperage of the box, meaning you could run a subpanel of up to 200 amps.

What’s important is that the subpanel is safely and correctly connected to the main panel and that you don’t overload the service panel.

  1. Can grounds and neutrals be connected in a subpanel? 

Ground and neutrals should only be connected at the last point of disconnect, which happens to be on the main panels only, not on the subpanel.

  1. Can I run a 100 amp sub-panel on 200 amps main?

You can definitely add the 100 amp breaker to your 200 amp as long as it is not overloaded. However, to start adding the subpanel, you must first calculate how many yards it will be from the main panel to the subpanel. 

  1. Should a sub-panel have a grounding rod?

All subpanels in separate buildings require at least one, and sometimes two, grounding electrodes. Only ensure to refer to the local code requirements.

  1. Why do grounds and neutrals have to be separated in a sub-panel?

If grounds and neutrals are connected at a sub-panel in a layman’s language, they will not have separate paths back to the service board. 

This means you will have current on the grounding conductor posing a danger to anyone working on the circuit.


It is not safe working on an open electrical service panel with both the door and the protective cover removed. 

Unlike the shock from a receptacle, which may or may not be fatal, a shock from the service lugs will most certainly be fatal or cause serious damage.

In the service panel, two protruding heavy black wires access the panel from the top of the box. These are the ends of the service wires that come into your house from outside bearing heavy voltage. Avoid any contact with these wires or anything touching these wires by all means. is owned and operated by Hubert Miles is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to also participates in affiliate programs with other affiliate sites. Hubert Miles is compensated for referring traffic and business to these companies.

Hubert Miles

I've been conducting home inspections for 17 years. I'm a licensed Home Inspector, Certified Master Inspector (CMI), and FHA 203k Consultant. I started to help people better understand the home inspection process and answer questions about homeownership and home maintenance.

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