The area of wireless sensor networks is one of the emerging and fast growing fields in the scientific world. This has brought about developing low cost, low-power and multifunction sensor nodes. However, the major fact those sensor nodes run out of energy quickly. In the research area of wireless sensor networks the power efficient time is a major issue. There are various routing protocols in which optimal routing can be achieved in the context of power. In this paper, the authors intend to discuss some of the major power-efficient hierarchical routing protocols or power efficient routing technique for wireless sensor networks.