The advancements in the wireless communication field make possible to have wireless sensor networks with large number of sensors deployed in the vast field. These sensors have capability of continuously sensing, processing data as per requirement and transmitting them to base station for the further analysis. But the major constraint with wireless sensor networks is the small sized sensors have stand-alone batteries i.e. limited power available to the sensor to perform various tasks. Thus this motivates the researcher to work on proposing various techniques which make wireless sensor networks energy efficient.