Owing to the immense climate changes recently, the city of Hamburg has decided to allow the purchase of only emission-free buses for public transportation. Meanwhile, Hamburg focuses on the implementation of electric buses. For this purpose, the two public transportation companies in Hamburg which are the Hamburger Hochbahn AG (HOCHBAHN), and the Verkehrsbetriebe Hamburg-Holstein GmbH (VHH) decided to build new charging infrastructure for electric bus depots. In addition, they started by electrifying their existing stations. This study proposes an optimal method for electrifying bus depots by modularizing the subsystems in electrical power systems. An approach that allows the study of different configurations of power system components. Analyzing these configurations results in the conclusion of the most technically feasible configuration, achieving the lowest cost. Furthermore, the model objectives include reducing the required area, which is a challenging criterion for bus depots in many cities. Mixed-Integer Quadratic Programming (MIQP) is used to generate this combination based on predefined constraints that must satisfy all implemented constraints of the system.