Sizing this sub-panel correctly requires a dual focus: determining the necessary electrical capacity, measured in amperage, and the physical capacity, which is the number of available breaker spaces. Selecting the right size is paramount for both safety and functionality. This post. Amps, Spaces, and Limits - Engineer Fix What Size Sub Panel Do I Need? Amps, Spaces, and Limits A sub-panel serves as a secondary electrical distribution point, extending your home's power service to a remote location like a garage, workshop, or dedicated basement space. While many families are familiar with these boxes, there is often a lack of understanding regarding their specifications and proper. Why keep neutral and ground separate in a sub-panel? What wire size should you use for a sub-panel? When you choose a sub-panel for your garage or shed, you need to think about what power you use now and later. What Are Electrical Box Dimensions? Electrical box dimensions typically refer to: Correct dimensions ensure:. Sign up for emails & save 10% on select home decor.