Electric utility resource planning traditionally focuses on conventional energy supplies. Nowadays, planning of renewable energy generation and its storage has become equally important due to the growth in demand, insufficiency of natural resources, and policies for low carbon footprint. We propose to develop a simulation based decision making framework to determine the best possible combination of investments for electric power generation and storage capacities. The proposed tool involves a combined continuous-discrete modular modeling approach for processes of different nature within this complex system, and will aid utility companies in resource planning via multi-objective optimization in a realistic simulation environment. The distributed power system considered has four components including energy generation, storage, transmission, and electricity demand. The proposed approach has been demonstrated for the electric utility resource planning at a scale of the state of Florida.