Electrical Service Panel Basics Homeowners Should Know

Shut Off Circuit Breaker to Heater

Lee Wallender

You may know it as a metal panel located in a distant part of your home that you rarely think about it. Then perhaps the power goes out in the kitchen because you turned on the blender. Hitting the reset button on the countertop GFCI outlet doesn't fix the problem. Suddenly you need it: the electrical service panel box.

Homeowners might visit their electrical service panel box no more than once a year. For older homes with aging electrical systems, it might become a routine visit. For newer homes, there may never be a need to visit it.

Understanding the basics of your home's electrical service panel will keep you safe and your home well-lit and energized. You'll 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.

What Is the Electrical Service Panel?

The electric service panel is the connection between the external wires coming from the street and the internal wires of your home's electric system. The service panel is the central distribution point that connects the service wire or service drop—the main wire coming from the outside into the house—to the exit wires that split off and service different parts of the house. These exit wires are called branch circuits or branch wire circuits. 

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

Circuit Breaker Service Panels and Fuse Boxes

Electric service panels have a number of different names: fuse box, fuse panel, circuit breaker panel. Today, most homes have what is officially called the electrical service panel, or simply, the service panel. A circuit breaker panel is not exactly the same as the fuse box because it has mechanical, toggle-switch circuit breakers, not fuses, but it does perform the same function. The older fuses screw or pull in or out, as opposed to the rocker-style method of installing and removing circuit breakers.

All of your home's power is located in the service panel. The electrical service panel provides 100, 200, or more amps of power to a home. Homes built between 1950 and 1965 may have these 60-ampere fuse boxes, often with four fuses. Power comes into the house from a service drop, connects to the service lugs within the service panel, and is split into separate circuits throughout the house.

Where to Find the Electric Service Panel

By its nature, the main service panel is usually kept away from the main household activities. Likely locations:

  • Garage
  • Basement
  • Hallway that leads to the garage or outdoors
  • Pantry adjacent to the kitchen
  • Closet

While not typical, a service panel may be found on the outside part of an exterior wall, especially in the case of older fuse boxes.

One way to find your electrical service panel is to first go outside and locate the service drop and service head on your roof. The service panel should be directly below in one of the home's stories. For buried power lines, usually the line will start at the street and connect to the home near the front or side of the home.

Electrical Service Panel Components

  • Outer panel door that swings open
  • Protective cover with spaces for the circuit breaker switches
  • Lugs or main breaker and thick wires that go up and connect to the service drop
  • Circuit breakers
  • Open or spare spaces for extra circuit breakers (optional)
  • Assortment of wires that run from the circuit breakers to the circuits that service areas of the house

Electrical Service Panel Safety Considerations

When the service panel's outer door is closed, the service panel is safe to touch under normal conditions. When the outer door is open and the circuit breakers switches are exposed, the panel is still safe to touch under normal conditions.

It is dangerous to work on an open electrical service panel with both the door and the protective front 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 seriously hurt you. In the service panel, two black heavy-gauge wires enter the panel from the meter base or a remote disconnect. The main entrance cable can enter the panel from the top, bottom, or even the sides. These are the ends of the service wires that come into your house from the outside. Avoid touching these wires or anything that these wires touch.

With that protective cover removed, shutting off the panel's main circuit breaker switch will not necessarily keep you safe. The main breaker cuts off the power to all of the home's branch circuits, but it doesn't not shut off the power coming into the panel on the utility service lines or to the lugs the lines are connected to.

While it is often easy enough to be cautious of areas in the service panel that your hands touch, be especially careful of tools that you are holding. The exposed service panel, screwdrivers, wire cutters, wire strippers, pliers, and more are items that can potentially touch parts of the service wires and transmit an electric shock to you.

Installing Additional Circuit Breakers

You can add more circuits and circuit breakers inside your electrical service panel box as long as there are spaces. In many cases, the service panel will have available spaces. Some older homes may have completely filled out their spaces. In this case, an electrician can install a new, larger service panel box or add a smaller sub-panel and feed it from the main panel. This will require you to move older circuits to the sub-panel to make space for the feeder breaker.

Generally, you can determine if there are more spaces by looking at the metal knock-outs on the panel itself. Any space that is not knocked out should be available for the insertion of another circuit breaker, but not always: Remove the cover to see how many open spaces are available.

Do-It-Yourself Electrical Panel Repairs and Remodels

Homeowners are allowed to work on the service panel, but many choose to avoid this for safety reasons. Most homeowners only have the experience of opening the outer door of the electrical service panel to flip on a disabled circuit breaker.

Since you own the service panel, you are allowed to work on its interior section for any type of work. The most common activity to remove and replace a circuit breaker.

Many seasoned do-it-yourself homeowners still choose to call in an electrician when it comes to any work that involves removing the protective front cover.