No, a breaker box, also known as an electrical panel or distribution board, does not necessarily have to be installed on an outside wall. The specific placement of a breaker box can vary depending on factors such as local building codes, available space, and the design of the building.
In many residential and commercial buildings, breaker boxes are commonly located in basements, utility rooms, garages, or even closets. These areas are typically chosen for easy access and to minimize the length of electrical wiring runs. However, it's important to note that local electrical codes may have specific requirements for the placement and accessibility of breaker boxes, so it's advisable to consult with a qualified electrician or refer to the applicable building codes in your area.