We focus in this paper on energy management strategies for a mobile network equipped with battery storage capacity as well as local energy production capability, and powered by a smart grid. At each time instant, the mobile network operator has to decide whether to operate its network based on its own energy resources or the smart grid ones, with a possibility to sell energy to the smart grid as well. We formulate our problem using Markov Decision Process (MDP) and derive an optimal, offline policy which minimizes the operator energy bill, using dynamic programming algorithm. We show the optimality of our solution by numerical comparison with the solution obtained through linear programming. Our numerical applications allow to further understand when the operator has an incentive to buy energy, whether it is beneficial for it to act as an energy seller, the size of the battery to deploy, as well as the robustness of our offline deterministic policy to estimation errors