With the right guidance and step-by-step instructions, anyone can easily install an electrical box in their shed. This guide will take you through what you need to know. This advice also applies to log cabins, summerhouses, and all types of garden rooms. Whether. Installing a separate breaker box, known as a subpanel, in a shed is necessary for safely distributing electrical power for tools, lighting, and outlets. Because this project involves high-voltage. This guide takes you through the essentials of running electricity to a shed, including preparation, permissions, wiring, materials and installation basics.