The task of increasing the efficiency of the domestic electric power industry is important for ensuring the sustainable development of the country. Today, the most efficient technology for producing electricity in large volumes is based on the use of a binary steam-gas cycle. At the same time, the potential for increasing the efficiency of combined-cycle power units remains quite high. In particular, a possible way to increase energy efficiency may be to reduce the consumption for cooling the hot path of a gas turbine by switching from air to steam coolant. The use of air as a coolant has found wide application due to the possibility of its intake from the compressor stages, but the thermophysical properties of the air environment predetermine a relatively high consumption for the cooling system and, as a consequence, a reduced level of energy efficiency of a gas turbine unit. An alternative solution may be to use water vapor taken from a steam turbine or waste heat boiler as a coolant. Such a transition will lead to a reduction in cooling costs due to ensuring the required level of heat transfer at lower cooling flow rates. The objective of the work is to develop and study combined-cycle power plants with steam cooling of gas turbines and an additional cycle on a low-boiling coolant for utilization of low-potential heat of exhaust gases. In this work, a method for recalculating an air coolant to a steam one is described and estimates of the effect of such a replacement on the total consumption of the cooling medium for the GTPP-160 gas turbine unit are given. In addition, based on mathematical modeling, it was found that in a trinary cycle, replacing the air cooling system with a steam one will lead to an increase in net efficiency by an average of 1.23% when extracting steam from the steam turbine compartment and by 0.53% when generating steam in a separate low-pressure steam generator.