In most Wireless Sensor Networks applications users would expect to achieve good service in terms of reliable retrieved accurate data. One technique to improve the level of data accuracy is to use fault tolerance techniques such as redundancy that would cause the energy of the system to deplete quickly. In this paper we address the problem of reliable wireless sensor network and provide the design and the analysis of an algorithm that model cluster-based structured Wireless Sensor Networks with the objective of achieving suitable reliability level requirements to extend the whole system lifetime. Reliability is defined as the probability that a sensor node will perform its intended function during a specified period of time under stated conditions. We analyze the effect of redundancy on the system reliability and the energy consumption level of the Wireless Sensor Networks model. Throughout the analysis we derived an expression for both the reliability and the energy consumption in terms of redundancy level parameter. Parameterizing the reliability and energy consumption would give the system designer the ability to select the suitable value of the redundancy level in order to satisfy different performance criteria such as maximizing the system reliability and achieving minimum energy consumption at the same time.