This paper presents an advanced methodology to install energy storage systems under network uncertainties. The uncertainties are related to solar and wind powers. The proposed problem minimizes the operational cost of generating units by coordinated energy storage planning and generation rescheduling. The problem is expressed as a stochastic mixed integer linear programming and solved using GAMS software. The simulations are carried out on an IEEE 24-bus test case including one wind unit and one solar power plant. The introduced stochastic problem is compared with the deterministic one in order to demonstrate its significance and effectiveness.