The continuing depletion of fossil fuels and the growing restrictions for greenhouse emissions, leads to reprocess wasted heat generated by power plants. For this purpose, Combined Cycles Gas Turbine (CCGT) represent a strong technology to obtain, an increase of performances and competitive costs within global market. To design the CCGT configuration, energy engineering companies should define and analyze the performances of bottomer cycle, imposing operating parameters of steam turbine and heat recovery boiler. Usually, these plant components are supplied by different manufacturers so the plant could not be globally optimized. Considering a steam turbines manufacturer as GE Oil&Gas, a high level of components integration, is a chance to optimize globally the bottomer cycle, determining the best machine in terms of efficiency and improving plant productivity. This aim could be obtained through the development of a high level of combination between company simulation codes and energy balance codes. In this paper, a two-pressure level combined cycle is examined and optimized. The best thermoeconomic configuration is obtained: first, imposing steam turbine efficiency and using literature costs correlations; then, acquiring the efficiency by a steam turbine industrial tool and considering real machines costs. Therefore, two distinct best configurations could be determined and compared. (C) 2017 Elsevier Ltd. All rights reserved.