Branch circuits are located in your home and in buildings. Instead of your home being one electrical circuit, it is divided into a number of branch circuits. Multiple devices can be attached to a single branch circuit. Having multiple branch circuits allows the electricity to stay on in the rest of your house if one branch circuit was to have a problem. Also, different circuits run at different amperages, like 15 and 20 amps. Different amperages call for different wire gauges. A 20 amp circuit would use a 12 gauge wire, while a 15 amp circuit will use a 14 gauge wire. Branch circuits are energized and de-energized at the service panel.