This document proposes an energy efficient routing protocol for wireless sensor networks called Enhanced K-Means Cluster-based Routing Protocol. It uses K-means clustering to divide nodes into clusters. Unlike other protocols, it considers an optimal fixed packet size based on radio parameters and channel conditions to decrease energy consumption. It also uses varying power levels for communication between cluster heads and members. Simulation results show it performs better than the conventional K-means based energy aware clustering protocol in terms of network lifetime and overall throughput.