In this study sensitivity analysis is performed for single, double-pressure, and triple-pressure heat recovery steam generators in a combined cycle power plant. Steam pressure, evaporator pinch point, and economizer approach temperature differences are taken as design parameters. Temperature-heat (T-Q) graphics of heat recovery steam generator (HRSG) designs and the effects of design parameters to the plant efficiency, net power production, and heat transfer areas are obtained. The calculated results are useful to compare single and multipressure HRSGs in a combined cycle power plant scheme. In single-pressure, double-pressure, and triple-pressure HRSG, net power increment is approximately 0.05, 0.28, and 0.29% at every 10-bar inlet pressure increment. The net power output of the cycle decreases with increasing evaporator pinch point temperature difference. For single-pressure HRSG, this decrement is approximately 0.54%, whereas for double-pressure and triple-pressure HRSG it is approximately 0.21% and 0.17%, respectively. For every 1 degrees C increment in economizer approach, temperature makes a decrement of approximately 0.09% and for double-pressure and triple-pressure 0.037% and 0.018%, respectively. However, net heat transfer area is also decreased and it is directly related to the first investment cost of the HRSG. Therefore, approach temperature and pinch point temperature should be taken into account for the optimum design of heat recovery steam generators. DOI:10.1061/(ASCE)EY.1943-7897.0000063. (C) 2012 American Society of Civil Engineers.