One of the most important issues of wireless sensor networks is how to transfer information from the network nodes to a base station and choose the best possible path for this purpose. Choosing the best path can be based on different factors such as energy consumption, response time, delay, and data transfer accuracy. Increasing the network lifetime is the most challenging problem. One of the latest energy-aware routing methods is to use the harmony search algorithm in the small-scale sensor networks. The aim of this study is to introduce the harmony search algorithm as a successful metaheuristic algorithm for wireless sensor network routing in order to increase the lifetime of such networks. This study is intended to improve the objective function for energy efficiency in the harmony search algorithm to establish balance between the network energy consumption and path length control. Therefore, it is necessary to choose the initial energy of each node randomly from a certain range as the path energy consumption should be low to choose a path which can consider the residual energy. In other words, a path should be chosen to establish balance between the network energy consumption and the minimum residual energy. The simulation results indicate that the proposed objective function provides a longer lifetime by 26.12% compared with EEHSBR.