The article characterises the properties of steam and special thermal oils as the basic heating media on motor ships. The features of the heating installations have been presented with the particular attention drawn to thermal oil installations in which exhaust gas heaters have been employed. Also an example of the comparative exergetic analysis has been included demonstrating the comparison between steam generation in exhaust gas boiler and oil heating system in the heater, assuming the identical heat flux transferred in the boiler and the heater from the exhaust gas to the heating medium (steam and thermal oil) and assuming identical increase of exhaust gas entropy in the heat exchangers under examination