WSNs are envisioned to consist of many small devices that can sense the environment and communicate the data as required. The most critical requirement for widespread sensor networks is power efficiency since battery replacement is not viable. Many protocols are proposed to minimize the power consumption by using complex algorithms. However, it is difficult to perform these complex methods since an individual sensor node in sensor networks does not have high computational capacity. On the other hand, many sensor nodes should transfer the data packet to the sink node that collects the required data. Therefore, the operations of the sensor nodes over the route are terminated. It is difficult to deliver the data packet to the sink node even if some sensor nodes are active. In this paper, an introduction of WSNs is presented with a deep insight into the power-aware routing protocol for sensor networks. The protocols considered are LEACH,VGA and PEGASIS. In addition, a comparison of these protocols is also presented.