In this study, the performance of a thermal power plant has been examined using the actual data from 2007 to 2012 in terms of thermal efficiency in boilers, turbines and pipelines. According to the calculated values, it has been seen that the pipe efficiency and the boiler efficiency show opposite behavior and also the pipe and boiler efficiencies have characteristic behaviors that are directly proportional to each other. With these impressions, it can be seen that the performance changes in the plant depend on the changes in the regions. The findings also show that any performance loss is not observed due to reasons such as material fatigue in the plant, while periodical and instantaneous changing parameters change the performance values. Alterations in the plant efficiency are evaluated by graphs and suggestions are made regarding the improvements that can be applied to the plant.