Recently, a tremendous interest has been concentrated on the design and development of wireless sensor networks (WSNs) — distributed systems comprised of numerous wireless, sensor devices deployed densely in a sensing area. Battery powered sensors need efficient management due to limited energy resources, and energy conservation is a vital design issue that needs to be boosted in order to increase the lifetime of a network. The main contribution of this paper is the design and implementation in testbed networks an energy aware routing protocol SLE-AODV for secure communication in a wide area WSN. SLE-AODV is developed based upon Ad hoc On-Demand Distance Vector (AODV) and Low Energy Adaptive Clustering Hierarchy (LEACH). It encrypts transmitted data using Advanced Encryption Standard (AES). The results of experiments conducted in the laboratory confirm significant energy savings that lead to a network lifetime increase.