Grati Block 2 Combined Cycle Power Plant consist of three gas turbines consist of unit
2.1, 2.2 and 2.3 with 100 MW net capacity. Unit 2.1 PLTG thermal efficiency was affected by the change of compressor inlet air temperature. Unit 2.1 PLTG thermal efficiency increase when compressor inlet air temperature decrease. Therefore, for identifying the effect of compressor inlet air temperature on unit 2.1 of PLTG thermal efficiency, the comparation of unit 2.1 PLTG thermal efficiency data analysis has been conducted. The calculation results show that the unit 2.1 PLTG thermal efficiency at compressor inlet temperature of 298,75 K, 301,45 K and 302,75 K respectively is 30,14%, 29,25% dan 29,09%.Then simulation result of Gatecycle software is 31,26%, 31,22% dan 31,19%. In conclusion, if compressor inlet air temperature is high, then unit 2.1 PLTG thermal efficiency is low.