The purpose of this work is to explore the possibility of thermally combining steam reheat power plants with fuel oil-fired diesel generating sets as a combined diesel-steam cycle. These generating sets are electrically connected to the power plant node. The steam unit (mono-block) chosen for this work is 100 MW. Three cases of utilization of waste heat from the fuel oil-fired diesel gen sets in the form of feed water heating repowering are proposed. This way of using the diesel-steam combined cycle as re-powering of the steam power plant under study, modify the classical solution of repowering with gas turbines, when replaced by fuel oil diesel engines. This composition way has not been found in the consulted bibliography. The three variants proposed were calculated and the resulting decrease in fuel consumption was determined for each one. Another original variant, which allows for the utilization of all the possible heat released by the generator sets exhaust gases, also produces reductions and allows for greater operational flexibility, but it must further be studied in detail.