The purpose of this study is to develop the general-purpose assessment method for energy system which covers from demand sides to supply sides in consumer and business facilities. In this report, the energy saving simulation is shown for football stadium that has a characteristic energy consumption change compared with other facilities. The energy consumption problem from simulation is shown by getting thermal load daily data and event schedule for a year. From this, the high-cost operation of heat source equipment has become cleared as one of the typical problems. Then the methods for energy saving and economic efficiency by equipment replacement and changing heat source are shown using simulation and the best-available heat source formation is proposed.