Wireless sensor network-a special case of ad hoc network, have emerged as a new technological vision in the field of wireless. There are various existing protocols and techniques from traditional ad hoc networks, that are relevant for wireless sensor networks, but there are also some basic differences which lead to the design of new protocols in WSNs. One of the key issue is prolonging the lifetime of its power constrained nodes. There are many new protocols explicitly designed for sensor networks where energy consumption and node lifetime are of vital contemplation. Cluster based routing algorithms have a unique potential for conserving energy in sensor networks. In this paper, the authors study and compare the energy efficiency of three protocols namely-AODV, LEACH, and LEACH-E, using Castalia simulator.