Recently, a residual battery and a thermal storage tank (TST) have become increasingly important for controlling a power system frequency because they enhance the amount of energy generated from renewable resources. Although there are many studies about system optimization without storage systems, they are included in few optimization studies. Some mathematical programming methods have been used to optimize an operation schedule for these systems. Although they can theoretically derive results, their execution time is overly long. Therefore, the authors have used metaheuristics to develop an optimization method for operating a residual battery, a TST, and output of heat sources. This method is faster than mathematical programming methods for deriving a semi-optimal solution for an energy system including a residual battery and a TST.