Home Electric Repair, Meyer Electrical Services Inc.
Written by Walt Meyer

Electrical Subpanel Basics for Homes – Part 1

The main service panel, also known as the circuit breaker box or load center, is the heart of every home’s electrical system. It is where the utility company’s electrical feed enters a house from the meter. The main service panel then distributes electricity to the branch circuits of the home.

An electrical sub panel performs like a smaller service panel with its own circuit breakers, distributing power to an area of a home or a nearby structure. A subpanel is installed in a convenient and accessible location for its service area.

Why Subpanels Are Needed

Some houses need subpanels to add circuits to a location situated far from the main service. Subpanels are often required for a garage or guest house on a home’s property. Usually rated at 60 to 125 amps, a subpanel’s capacity will depend on the electrical usage anticipated for its service area.

For supplying power to large appliances and car chargers, additional circuits will be split off from a subpanel to handle their power demands. Electrical subpanels located on detached dwellings will each require its own grounding system.


An electrical sub panel needs two hot wires that are connected to a 240-volt double-pole breaker inside the main service panel. In addition, a neutral wire and a ground wire will be required. This wiring configuration is described as a “three-wire cable with ground.” Acting as feeder wires, the two hot wires supply all the electricity to a subpanel.

A three-wire cable with ground is connected to a 240-volt main breaker inside a subpanel, which then provides power to two hot bus bars. Connected to the bus bars, circuit breakers are used for distributing electricity to the branch circuits running from a subpanel.

Sizing of Subpanels

The proper sizing of subpanels to meet the electrical load anticipated presents some challenges. The two factors are the amount of available power load required and the capacity of the main service panel.

For example, a home equipped with a 200-amp main service panel will have no issue installing a 100-amp subpanel for powering a barn, garage, or shed. It should also have no problem feeding a 60-amp subpanel used for powering general-use outlets or lighting in a newly added room.

Part 2 will discuss the Benefits of Electrical Subpanels and Construction Savings.

Electrical Services You Can Trust

Founded in 1991, Meyer Electrical Services provides home and commercial electrical services in Maryland, Virginia, and D.C., where we are licensed and insured. Based in Bethesda, our team proudly serves all of Montgomery County. Receive a free consultation for custom electrical work today by calling (301) 941-1400.