Researchers in the field of internal reforming molten carbonate fuel cells (MCFC) propose two different configurations: (i) direct internal reforming, and (ii) indirect internal reforming. This paper reports the results of a study on the influence of the operating parameters on the energy balances of a MCFC fuelled with indirect internal reforming (IIR-MCFC). This analysis, carried out by using a mathematical model, identifies the temperature, the steam/carbon ratio, the current density, the useful heat fraction and the fuel-utilization coefficient as relevant parameters to determine the overall energy efficiency of the system. The results emphasize the influence of the working temperature (893 to 973 K) and the steam/carbon ratio (1.5 to 2.5) on the electrical efficiency and on the methane conversion. A detailed balance of the thermal power contributions has been determined, as well as the compositions of exhaust gases for various conditions. The most meaningful conclusion confirms the reliability of this system for the production of electricity with an efficiency in the order of 35 to 40%.