The paper analyzes a new concept of integration of combined cycle with the installation of supplementary firing. The whole system was enclosed by thermodynamic analysis, which consists of a gas-steam unit with triple-pressure heat recovery steam generator. The system uses a determined model of the gas turbine and the assumptions relating to the construction features of steam-water part were made. The proposed conception involves building of supplementary firing installation only on part of the exhaust stream leaving the gas turbine. In the proposed solution superheater was divided into two sections, one of which was located on the exhaust gases leaving the installation of supplementary firing. The paper presents the results of the analyses of which the main aim was to demonstrate the superiority of the new thermodynamic concept of the supplementary firing over the classical one. For this purpose a model of a system was built, in which it was possible to carry out simulations of the gradual transition from a classically understood supplementary firing to the supplementary firing completely modified. For building of a model the GateCycle™ software was used.