A methodology of assessing a cogeneration system on a ship is proposed. Given the mass flow rate of exhaust gas and cooling seawater and the inlet temperatures of the gas and seawater, the net power of this system can be obtained through an iterative method. The parameters of mass flow rate of exhaust gas, heat transfer area of boiler and condenser and outlet temperature of the gas from the boiler are considered. In the heating process, the boiler tubes contain superheated, saturated and subcooled sections. It is shown that the dimensionless saturated area of the boiler increases with exhaust mass flow rate, whereas the superheated region tends to decrease on increasing the mass flow rate of flue gas at a fixed exhaust temperature. As for the subcooled portion, no significant change is observed. The power consumption of the working fluid circulating pump increases as the exit exhaust temperature from the boiler decreases. In addition, the more net work the turbine produces, the lower is the outlet temperature of the working fluid in the condenser for a fixed mass flow rate of exhaust gas. The net output of the cogeneration system is larger for a larger mass flow rate and a smaller exit temperature of the exhaust. Finally, an experiment is conducted to validate the proposed model. (c) 2007 Elsevier Ltd. All rights reserved.