In a district heating and cooling system, for example the Beijing combined heating. Cooling and power (CHCP) system studied here, high temperature water generated by cogeneration plants circulates through a network between the plants and the heating substations. In heating substations, high temperature supply water from the network drives absorption chillers for air-conditioning in the summer, satisfies space heating demands in the winter and provides domestic hot water using heat exchangers throughout the winter and provides domestic hot water using heat exchangers throughout the year. This paper studies the significant effect of the parameters, i.e. the supply and return water temperature in the network ,on the CHCP system energy consumption for cooling and for domestic hot water.