Electrical supply from the utility company enters your home or property from the main meter and then towards the main service panel. The main panel has circuit breakers that automatically shut off when there’s overloading in a circuit. Every home has a main panel.
An electrical subpanel is like the main service panel but smaller. They are used to supply power to rooms or areas that are particularly far from the main panel, such as garages, storage buildings, and outhouses. Just like the main panel, the common types of circuits are power circuits, light circuits, and appliance circuits.
The reason why a subpanel is installed is convenience. It is easier to turn off the subpanel than to go all the way to the main panel. If you use power tools in the garage, it will trip now and then because of the high load. Resetting the circuit is done faster when the subpanel is in the garage.
Another reason is that it is cheaper to install one set of feeder wires from the subpanel to the main panel that to have multiple wires from outlets going to the main panel. More wires mean more materials and higher labor cost. Lastly, a subpanel is the best solution when you need additional slots for circuits that no longer fit in the main panel.
Before you buy a subpanel, you need to make sure that it is the right size. You need to think about how much load you need and then add some extra for the contingency. To get the right size, you should ask an electrical professional to compute it for you. He will also tell you how many circuit slots you need. Just let him know about the appliances and amount of lighting that you will use.