This chapter provides a general procedure for designing electrical systems for commercial buildings. In particular, general design guidelines are outlined for lighting and power panels, motor control centers, main distribution panels, and unit substations. Moreover, short-circuit currents at various locations within the electrical distribution system are estimated using simplified analysis methods. Throughout the chapter, step-by-step calculation procedures are outlined with specific examples. Tables and diagrams are provided to further assist the readers in designing safe electrical systems for commercial buildings. A case study for designing a radial electrical distribution system for an office building is described with detailed calculations and specifications.