How to plan the energy system is one of the keys for constructing the Environment -Friendly City. For this reason, a great number of surveys for utilizing unused energy have conducted by a planner. In regard to unused energy, the heat from incineration plants classify as a unused energy having high-exergy-energy. From this point of view, It is studied about the plant systems providing heat to district heating & cooling(D.H.C) and producing electric power. It is divided four system models as system I (10K [kgf/cm2] vapor as outlet of boiler, supply for 10K vapor and return to 60℃ as supply condition of district heating), system Ⅱ (30 K vapor as outlet of boiler, supply for 5K vapor and return to 60℃ as supply condition of district heating), system Ⅲ (30 K vapor as outlet of boiler, supply for 85℃ hot water and return to 60℃ as supply condition of district heating), system Ⅳ (30 K vapor as outlet of boiler, supply for 47℃ hot water and return to 40℃ as supply condition of district heating). The results from the upper condition of four system, System Ⅱ got a proper on economical benefits and system Ⅳ calculated as benefiting on energy saving effects, and suggest indifference curve as the total evaluation method of both economical benefits and energy saving.