Conservation of energy has become a major concern all over the world. Especially in the domestic area, public buildings, and office buildings, energy supply systems have to be optimized swiftly balancing with the time-dependent energy demand. This paper discusses the exemplary energy assessment of the cogeneration and air-conditioning system on Keio University Shonan Fujisawa Campus with approximately 5,000 students and 200 faculty members. The purpose of the cogeneration system consisting of prime mover and exhaust heat recovery equipment is a conlribution to energy conservation. Exhaust heal of lhe prime mover can be reutilized in form of heated or chilled water by the exhaust heat recovery equipment. Optimized reutilization of exhaust heat shall bring the main benefit for energy conservation. Therefore, the effectiveness of the cogeneration system has been evaluated based on collected annual data of energy consumption on the campus. Furthermore, curtailment of air-conditioning systems during peak load caused by the congestion of the grid power has been examined. In order to optimize the energy management under these conditions, the forecast of power consumption has been discussed, and the relation of power consumption to air temperature has been examined.