A control system of a Demand-Based Operation of a DH/DC network (1;50) for a distributed control of local heating and/or cooling flows of heating or cooling fluids in local units (41,42,43;81,82,83), respectively, from heating and/or cooling sources (16,18;66,68) through local heating and/or cooling systems of the local units (41,42,43;81,82,83) using local thermostatically controlled valves (19h,19c;69h;69c), wherein the local thermostatically controlled valves being adapted to set the local heating and/or cooling flows in the local units according to a local measured temperature, wherein control data, selected from any of: local return temperatures, valve positions, local flow rates, and/or local cooling and/or heating medium pressures in the local heating and/or cooling systems, are brought to a central monitor (25;75), wherein the central monitor being adapted to monitor the control data and to reset a supply temperature at the heating and/or cooling sources in a step-wise manner according to a performance of the local heating and/or cooling systems, and wherein, if the central monitor (25;75) detects that in one of the local heating and/or cooling systems of the local units (41,42,43;81,82,83): i) a flow rate reaches an upper or a lower limit when local flow rates are selected as said control data, or ii) a return temperature reaches an upper or a lower limit when local return temperatures are selected as said control data, or iii) a thermostatically controlled valve has reached an upper or lower limit when valve positions are selected as said control data, or iv) a pressure drop is below a design level when local cooling and/or heating medium pressures in the local heating and/or cooling systems are selected as said control data, then the central monitor is adapted to increase or decrease the supply temperature of the heating and/or cooling source (16,18;66,68) in a step-wise manner. wherein the local thermostatically controlled valves being adapted to set the local heating and/or cooling flows in the local units according to a local measured temperature, wherein control data, selected from any of: local return temperatures, valve positions, local flow rates, and/or local cooling and/or heating medium pressures in the local heating and/or cooling systems, are brought to a central monitor (25;75), wherein the central monitor being adapted to monitor the control data and to reset a supply temperature at the heating and/or cooling sources in a step-wise manner according to a performance of the local heating and/or cooling systems, and wherein, if the central monitor (25;75) detects that in one of the local heating and/or cooling systems of the local units (41,42,43;81,82,83): i) a flow rate reaches an upper or a lower limit when local flow rates are selected as said control data, or ii) a return temperature reaches an upper or a lower limit when local return temperatures are selected as said control data, or iii) a thermostatically controlled valve has reached an upper or lower limit when valve positions are selected as said control data, or iv) a pressure drop is below a design level when local cooling and/or heating medium pressures in the local heating and/or cooling systems are selected as said control data, i) a flow rate reaches an upper or a lower limit when local flow rates are selected as said control data, or ii) a return temperature reaches an upper or a lower limit when local return temperatures are selected as said control data, or iii) a thermostatically controlled valve has reached an upper or lower limit when valve positions are selected as said control data, or iv) a pressure drop is below a design level when local cooling and/or heating medium pressures in the local heating and/or cooling systems are selected as said control data, then the central monitor is adapted to increase or decrease the supply temperature of the heating and/or cooling source (16,18;66,68) in a step-wise manner.