A sub panel is a smaller service panel that distributes power to a specific area of the home or other building on the property. It is essentially a satellite circuit breaker panel that has its own breakers and is usually installed in a location that is convenient to the area it serves.
The sub panel is fed by a double-pole 240-volt breaker at the main service panel, and this single feed circuit is divided into additional branch circuits at the sub panel.
Some homes require installation of sub panels for either additional circuits located a far distance from the main meter panel or for garages and guest houses. An electrical sub panel is typically rated 60 amp – 125 amps, depending on the current usage required.
Additional circuits for car chargers and other appliances would be branched off of this sub panel for these types of installations. An electrical sub panel on detached dwelling requires its own grounding system.
The National Electrical Code (NEC) has evolved in terms of safety when it comes to electrical panel grounding systems. An electrical panel proper grounding system consists of a conductor wire from the grounding bar located in the electrical panel, unbroken to the cold water pipe, ending at an 8’ft ground rod driven into the earth.
A garage, outbuilding, or a room addition might be a place to put an electrical sub panel. It may also be required for those who have just purchased an electric vehicle and need a dedicated circuit for their new EV charger.
The idea is to run a single set of feeder wires from the main panel to a sub panel, where the power will then be divided into multiple branch circuits serving that building or area of the house. The circuits running from the sub panel may power light circuits, outlet circuits, or appliance circuits—just like the main service panel.
Before you begin installing an electrical sub panel in your home or request this service from your local electrical contractor, ask yourself if you really need one. Check out our FAQs, where we share some insights from our electricians as they give us reasons to install a sub panel in the home, which type of sub panel is recommended, and where you should put a sub panel.
Frequently Asked Questions about Electrical Sub Panels
Do I need a sub panel?
If the service panel does not have room for new circuit breakers and you cannot use tandem breakers, an electrical sub panel may be the answer. A sub panel connects to the main service panel with a thick three-wire cable. Before scheduling an electrical sub panel installation, consult with an inspector to make sure you do not overload your system.
What electrical sub panel size do I need?
Sizing sub panels to the need of your anticipated load can be tricky. You’ll need to consider the amount of available power load you’ll need and what the main service has to offer. For instance, If you have a 200-amp main service, you’ll have no problem adding a 100-amp sub panel to feed a shed, garage, barn, etc. or a 60-amp sub panel to power lighting and general-use outlets in another section of your home. But if you only have a 60-amp service, to begin with and want to add a 60-amp sub panel, you’ll have to upgrade your main panel first to allow such a distribution addition.
When adding a sub panel, our electricians suggest adding at least a 12-slot circuit breaker panel.
This should provide ample room for lighting and general circuits. However, if you plan to add many 240-volt appliances like central air conditioning, baseboard heaters, water heaters, ovens, ranges, or 240-volt window air conditioners, then a circuit breaker panel with more opening may be required, as well as a circuit breaker panel with more openings and a larger main breaker rating.
What electrical codes should I be aware of?
Subpanels and main panels alike have specific rules that need to be followed according to the National Electrical Code (NEC). All electrical panels must have a minimum of 36 inches of clearance in front of the panel, 30 inches of clearance across the face of the panel, and a minimum of 78 inches above the floor.
If you can picture an invisible phone booth with an electrical panel on one wall, you’ll have a good idea of what is required. Now the NEC goes a little farther in requirements than that. The panel must be mounted in a dry location and have easy access to it. Only attach a panel in an area that is not exposed to flammable materials and never mount it where it is exposed to moisture like a bathroom or indoor swimming pool area or the like.
