Electricity consumption in the building sector continues to rise, accounting for approximately 60% of global energy consumption. This study implements a microcontroller-based Building Energy Management System (BEMS) to optimize energy consumption through temperature and lighting control in a miniature building. The threshold method is applied to automatically regulate fan and LED operations based on environmental conditions and presence detection (PIR). Test results demonstrate that the BEMS is highly effective, achieving an energy efficiency of 71,86% and an absolute energy saving of 18,2219 Wh compared to the conventional continuous operation method. This achievement significantly surpasses the initial research target, indicating BEMS's substantial potential in enhancing energy efficiency and occupant comfort