In this study, solar repowering of the Soma-A thermal power plant in Turkey is investigated using simulations. The Soma A thermal power plant began operation in 1957 and has served until 2010. In the current situation the installed capacity of the power plant is 44 MWel with two units. In the simulations full load and part load operations are considered and compared for three different cases: (1) current case; (2) solar steam generation; and, (3) solar feed water heating. Economic analyses are performed by using the simple payback method. According to the results, solar repowering of Soma A thermal power plant with parabolic trough type collectors can result in 14% power increment at full load operation of the boiler and 14% CO2 decrement at part load operation of the boiler. However, the economic analysis predicts that the payback time of solar repowering is approximately 10 years for a CO2 price per ton of 100 USD and unit electricity selling price of 0.24 USD/kW h. © 2012 Elsevier Ltd. All rights reserved.