Making targeted subsidies and the process of releasing energy market and specified criteria for quality of delivered energy to consumers shows the necessity in explanation of producing energy in Iran. In the meantime, Thermal power plants produce about 85% of electricity generation in Iran. Steam and gas turbine power plants have created the vast capacity of thermal plants power generation but the significant portion of this generated power is not in the sense of new energy policy. Therefore the reconstructing and improvement of thermal power plants has undeniable importance. In this paper, considering two major methods in reconstructing of the thermal power plants, eligible power plants have been presented. Results are being discussed according to the important economic parameters like electricity generation costs, capital return rate, cost benefit, annual interest and etc. In the meantime, estimation of changes in target plants in terms of technical and economical characteristics will have an effective role in our decisions it means the changes have been effected by considering features of current plants and their potentials. The efficacy of reconstructing on average efficiency, capacity and electricity generation cost can be effective parameters in future management decisions.