Optimal designs of a CCGT power plant characterized by maximum second law efficiency values are determined for a wide range of power demands and different values of the available heat transfer area. These thermodynamic optimal solutions are found within a feasible operation region by means of a nonlinear mathematical programming (NLP) model, where decision variables (i.e. transfer areas, power production, mass flow rates, temperatures and pressures) can vary freely. Technical relationships among them are used to systematize optimal values of design and operative variables of a CCGT power plant into optimal solution sets, named here as optimal solution families. From an operative and design point of view, the families of optimal solutions let knowing in advance optimal values of the CCGT variables when facing changes of power demand or adjusting the design to an available heat transfer area.Fil: Godoy, Ezequiel. UTN. FRRo. CAIMI; ArgentinaFil: Scenna, Nicolás José. UTN. FRRo. CAIMI; Argentina - CONICET. INGAR; ArgentinaFil: Benz, Sonia Judith. UTN. FRRo. CAIMI; ArgentinaPeer Reviewed