In today's technology driven world the growth of the data centers have been enormous to match the required needs of various institutions, organizations and governments etc. for storing data in a safe and secure manner. Similarly efficient use of electrical energy is gaining importance due to diminishing resources and ever growing demands. Therefore the efficient energy utilization is a must in a data center. In this paper we have discussed the architecture, electrical system and the cooling system of a data center in a generalized manner. Also all the basic required parameters for calculating the energy efficiency of the data center are considered. Suggested procedure can be utilized for the power consumption analysis of a data center and obtained results can help taking measures to improve the energy utilization of the data center