Anew method for determining the optimal heat-exchanger layout in a heat recovery steam generator and its operating parameters are presented in this paper. A robust mathematical model is developed, where arbitrary steam-pressure levels and steam-reheating levels can be set. The method considers all the possible heat-exchanger layouts, in both serial and parallel arrangements of steam pressure levels or steam reheating levels. The maximum thermodynamic efficiency of the steam-turbine cycle is set as the objective function. The results show that the optimal high pressure in heat recovery steam generator without reheating is in the region of subcritical pressures, whereas that for a heat recovery steam generator with reheating is in the region of supercritical pressures. In the case of similar water or steam temperature profiles in the heat exchangers of different steam pressure levels or reheating level, from a thermodynamic viewpoint, it is justified to use a parallel heat-exchanger arrangement. (C) 2017 Elsevier Ltd. All rights reserved.