Wireless sensor networks are catching up as the primary mode for monitoring and collecting data in physically challenging environments. They And applications in various fields varying from environment monitoring, military applications to monitoring patients in hospitals. The constraints due to their inherent features make routing in wireless sensor networks a big challenge. This paper covers Genetic algorithm (GA) based simple straight forward, address based shortest path routing in Wireless ad hoc sensor networks (WASN). The routing in packet switched multi-hop networks can be described as a classical combinatorial optimization problem i.e. a shortest path routing problem in graphs. The stress is on energy efficient routing where the network optimizes between efficient routing and maximizing life of the network. The results show that the GA is efficient for energy constrained WASNs due to their fastness in computation comparing to all other algorithms. © 2010 IEEE.