The main challenge in developing a VRE power plant is its power fluctuation and uncertainty. This usually causes system owner/ operator to specify certain requirement, such as ramp rate limit, min. unserved energy, or other criteria. One of the easiest ways to accomplish that is by equipping it with storage system such as battery. However, finding the right combination of size of the VRE source and battery can be tricky and is crucial. In this study, we will help our clients in determining the optimum combination between the size of the VRE sources and the size of battery that meet the predetermined criteria.