Everything to Know About Electrical Panels or Load Centers

A load center is the electric service panel that distributes electricity throughout the house. It is important to know what an electrical load center is when doing your own electrical work or when maintaining your house's electrical system.

What Is a Load Center? 

A load center is a metal electrical service box that receives incoming power from the utility company lines or from another load center. The load center distributes the power to electrical circuits throughout the home. Each circuit is protected with a circuit breaker. 

A load center is sometimes referred to as a panelboard, circuit breaker box, electrical panel box, or a fuse panel.

Load Center vs. Panelboard

For residential purposes, a load center and a panelboard are the same thing: an electrical power distribution center. The National Electrical Code (NEC) does not distinguish between a load center and a panelboard.

In some cases, panelboard refers to a deeper, surface-mounted board that holds bolt-in breakers and is rated up to 1,200 amps. This type of panelboard is rarely found in homes.

Types of Load Centers

Homes may have two types of load centers: a main breaker load center and a main lug load center. A main breaker load center includes a main breaker; a main lug load center has a single lug instead of a main breaker.

Main Breaker Load Center

A main breaker load center receives all incoming electrical supply to the house from the utility company overhead or buried power lines. The load center distributes the power to the home's branch circuits. Every home with electrical service will have a main breaker load center.

A lever-style main breaker provides overcurrent protection to all downstream branch circuits. A main breaker operates much like the smaller circuit breakers that are found in the panel. It can be manually turned off to stop the flow of all power to the house, plus it shuts off on its own in the event of a power surge.

Main Lug Load Center (or MLO)

A main lug load center, often called a subpanel, is installed downstream from a main breaker load center. A main lug load center is sometimes installed to expand the number of circuits in a home. In addition, it creates independent electrical zones—especially valuable when building an accessory dwelling unit or ADU. Not all homes have a main lug load center.

A main lug load center has no main breaker. Incoming power from the main breaker load center feeds into a central lug. This lug feeds into the line side of the lugs attached directly to the bus bar.

Main overcurrent protection is provided by the main breaker load center's main breaker. Circuits in the MLO also have their own individual overcurrent protection with the circuit breakers.

Other Load Center Features and Variations

• Convertible or combination load centers: Some main lug load centers can be converted to main breaker load centers by adding a main breaker.
• Surface-mounted load centers: Surface-mounted load centers mount directly to the wall.
• Flush-mounted load centers: Flush-mounted load centers are recessed in the wall between two studs and tend to be long and narrow.
• Renovation load centers: Renovation load centers are narrower than conventional flush-mounted load centers to accommodate older, thicker studs that allow less room for flush-mounted load centers.