In this study, the energy and exergy analysis of a 160 MW Cayirhan thermal power plant, which is operational in Ankara, Turkey, is performed. The effects of varying dead state temperatures on energy and exergy in the plant are investigated. Exergy destruction (irreversibility), entropy generation, per cent ratio to exergy destruction and heat loss, energy and exergy efficiencies are determined for the dead state temperatures ranging from 5 to 30 degrees C. The varying dead state temperatures do not have an effect on the energy efficiency (first law efficiency), whereas they affect the exergy efficiency (second law efficiency). The energy efficiency is computed as 42.76% for the whole plant. The exergy efficiency values for the whole plant are obtained as 35.62 and 32.97% for varying dead state temperature values between 5 and 30 degrees C respectively. It is observed that dead state temperatures directly affect the exergy efficiency of the thermal power plant. In addition, the comparison between heat losses and exergy destruction of the individual component of the plant shows that the maximum heat losses occur in the condenser, whereas the maximum exergy destruction occurs in the boiler for all the reference state temperatures. Furthermore, the analysis shows that the boiler is the major source of irreversibility in the plant.