NOVELTY - The controller has an increase rate computing unit for computing fuel increase rate. A reference setting unit sets a reference fuel increase rate based on which a determination is made whether waste heat increase control is to be executed to increase engine waste heat quantity corresponding to heat utilization requirement. A waste heat control unit determines whether the waste heat increase control is to be executed based on a comparison result between the fuel increase rate and the reference fuel increase rate.    USE - Waste heat controller i.e. waste heat reuse system, for controlling waste heat quantity of an engine e.g. internal combustion engine and spark ignition type multicylinder petrol engine, of a vehicle based on a required heat quantity along with a heat-utilize requirement.    ADVANTAGE - The controller controls engine waste heat quantity while restricting deterioration of fuel economy. The controller is designed such that fuel consumption per increased electric power has difference between multiple electric power sources, so that the fuel consumption can be reduced without varying the total electric power supplied from the electric power sources. The allocation of electric power supplied by the electric-power source is determined such that total electric power agrees with required electric power and the fuel consumptions per increased electric power of each electric power source agrees with each other, thus supplying required electric power to the electric loads from multiple electric-power sources, and hence restricting increase in computing load.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a heat source controller for controlling heat supply from multiple heat sources to a heat exchange portion mounted to a vehicle, comprising a required heat quantity computing unit    (2) an electric power source controller for controlling electric power supply from multiple electric power sources to an electric load mounted to a vehicle, comprising a required electric power computing unit.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of a waste heat controller.    Intake pipe (11)    Throttle valve (13)    Electric throttle actuator (14)    Fuel injector (15)    Spark plug (16)    Intake valve timing controller (18)