The design, installation and maintenance of electrical systems differ significantly based on power rating. In the Code of Practice for Electrical Installations, 600V is considered low voltage and is usually employed in commercial buildings in Singapore [8]. The usual electrical system components are: transformer, wiring, distribution equipment, protective device, lighting, standby/emergency power supply, and grounding and lightning protection system [9]. Many defects of electrical system occur due to other services that share the same service spaces (e.g. seepage through building components, mismatch of lighting grid, etc.). Information regarding these critical aspects should be conveyed to the relevant professionals at the outset of the project. The identified electrical system defects refer to (a) general performance and hazards; (b) transformer; (c) cable wiring; (d) distribution equipment; (e) Protective device; (f) Lighting; g) Standby/Energy/Power; (h) Grounding and Lightning Protection System and Earthing defects. Integrating predictive maintenance and maintainability issues at the design stage could maximise the electrical systems’ efficiency as well as the effectiveness of its performance throughout a building’s life cycle.