A Wireless Sensor Networks (WSNs) consists of many sensor nodes and these networks are deployed in different applications for monitoring environmental conditions. These sensor nodes are limited energy which limit the lifetime of a sensor network. In WSN's nodes are densely located, so there is duplication of data as multiple nodes sensing same event. Such duplication of data is responsible for wastage of node energy. Since energy saving is one of the important issues. So, data aggregation, data fusion should be used for saving energy.