Cloud computing is a major technological advancement in the field of computing and it is very advantageous to the user. It offers various computing utility services to the day to day life but the demand of Cloud infrastructure has greatly increased the energy consumption of data centers, which is a major big problem which the world is facing today. Cloud computing is a scalable for running various types of applications. In this paper, the authors have mentioned the concept of Virtualization which plays a major role in Cloud computing infrastructures. By using the concept of Virtual Machines (VM) and migrating the virtual machine to the physical server a cloud provider can reduce the energy consumption of data centers without violating the SLA and QOS.