Two types of sensors are used in a two-tiered wireless sensor network (WSN). In each cluster of a given environment, there are small and low-cost sensor nodes (SN) that sense the environment phenomenon and send their information to application nodes (AN). ANs remove redundant information and then transmit the data to base station (BS). Since the coverage of each cluster depends on the operation of its AN, power consumption of ANs is a critical factor in network lifetime. In this paper a power efficient data routing method to increase the network's lifetime in a two-tiered WSN is proposed which has fixed location ANs and BS. The proposed routing approach can be used in controlling the data flow routing path in time variant data bit rate WSNs in order to use the remaining power of the network as efficient as possible.