D ata center is a critical component in information technology infrastructure. The sustainability of data center operations is highly dependent on efficient and reliable power management. By looking at the existing conditions in the PT.XYZ data center where power can no longer supply the entire load and there is no redundant in its electrical system. Therefore, it is necessary to increase the tier from tier 1 to tier 2. This study aims to analyze and design a power management system in a data center based on the tiering level to increase energy availability and efficiency. The research methods used include literature studies to understand the concept of tiering in data centers, analysis of power requirements at various tiering levels, and design of an appropriate power management system. From the results of the data center design calculations, it was found that the data center is efficient and meets the requirements as a green data center with a Power Usage Effectiveness value of 1.7 and a Data Center Infrastructure Efficiency of 58%. In the electrical system design that was made using 4 UPS units with a capacity of 250 kVA and a generator with a capacity of 1600 kVA. That way the UPS can back up critical loads for 16 minutes. The electrical system is made of two sources and a reduntant system for the reliability of data center electrical power to be maintained. From the results of this study, when PLN goes out, power can be immediately backed up by a generator with a 1-minute time shift which is expected to perfect the previous electrical system and provide a reference for designing and implementing a power management system in the data center by considering the tiering level.