The main aim of energy efficient routing is to minimize the energy required to transmit or receive packets also called as active communication energy. Inactive energy is the energy which not only tries to reduce the energy consumed when a mobile node stays idle but also listens to the wireless medium for any possible communication requests from other nodes. To conserve energy, many energy efficient routing protocols have been proposed. Networks of small, inexpensive, disposable, smart sensors are emerging as a new technology with tremendous potential. Wireless sensor networks can be randomly deployed inside or close to phenomenon to be monitored. The advantage of these networks is the fact that they are self-configuring, which means that a sensor network can be deployed randomly on a battlefield, in a disaster area or in an inaccessible area without the need for human intervention. The energy supplies of nodes are not replenished or replaced and therefore nodes only participate in the network for as long as they have energy. This fact necessitates energy efficiency in the design of every aspect of such nodes. Energy consumption in sensor nodes occurs mainly due to computational processing and, to a greater extent, communication. The routing protocol employed by these sensor nodes can minimize the number of transmissions that nodes make as well as the computational complexity of routing path selection. It is therefore of critical importance that the routing protocol be designed with energy efficiency in mind.