Mobile sensor networks have received significant attention recently. Mobile sensors are deployed to achieve network load balancing, prolonging network lifetime, and improving network coverage, by monitoring critical areas where manual sensor deployment cannot be performed. To achieve these goals, energy estimation is one of the main constraints and concerns to consider, while deploying mobile sensors in a sensor field. Most of the energy models designed for sensor networks assumed static sensors. In this paper, we propose a comprehensive energy model to estimate the overall energy consumption through power dissipation, for both static and mobile sensors in the potential sensor fields. We calculate the total remaining lifetime of mobile sensor networks from the total power dissipation. By predicting the remaining lifetime of any network in different network scenarios at a given instance of time, an optimum network strategy can be designed for a given application.