The purpose of the research is to select the priorities for the development of various types of power plants and to substantiate the structure of generating capacities. An improved method has been developed for the selection of priorities for the development of various types of power plants, taking into account the service life and economic performance of the main equipment of power plants in variable modes based on equivalent operating hours. The influence of variable modes of combined-cycle gas installations on the service life of the main equipment (steam and gas turbines) is studied. The comparative efficiency of CCGT-450 in variable modes is calculated, taking into account the wear of the main equipment. As a result of calculations, it was found that with the minimum forecast prices for natural gas, the most efficient power plant (among those considered) is combined cycle power plant, which provides the lowest prime cost of electricity when operating in the base mode and the least increase in the prime cost of electricity when operating in an alternating mode.