A control system for a cogeneration unit, the cogeneration unit including a heat engine and an alternator, driven by the heat engine, which generates AC electricity for an electrical load. The control system includes a parameter sensing means for sensing one or more parameters, and providing a sensed parameter value for each sensed parameter. For each sensed parameter, a comparator means compares the sensed parameter value with a respective desired value and provides an error signal according to the difference between the sensed parameter value and the desired value. One or more controlling means use the one or more of the error signals to provide a plurality of control signals, such that each control signal is able to regulate one or more of the controlling characteristics of the alternator and a temperature of a body heated using energy from the cogeneration unit.