Today, electrical innovation is the most needed both for own use and for industry. Therefore, researchers create various innovations to improve efficiency. There are so many innovations being developed that the efficiency of the power plant can be improved. One such innovation is the use of turning gear operations in generation to rejuvenate generator turbines and improve efficiency. The purpose of this paper is to identify the effect of thermal efficiency of gas turbine operation for 12 month compared to one month operating of gas turbine. In this paper found that the thermal efficiency of turning gear operation for 12 months is 0.4059% higher than the thermal efficiency of turning gear operation for one month that is 0.0178%.