The banana samples were dried in a laboratory scale microwave oven at different powers of 200, 300, 400 and 500 W. The results showed that microwave power significantly influenced the total heating time and energy efficiency of drying processing. In this study, the measured moisture ratio (MR) values were fitted and compared with predicted values obtained from Midilli’s thin layer drying semi-empirical equation. Highest value of R2 and the lowest values of χ2 and RMSE for banana samples at different powers are obtained as 0.9999, 1.6618×10-5 and 0.0043 respectively. Also, within the range of microwave power values, 200–500 W, effective moisture diffusivities were found to be 1.4×10-5 to 5.52×10-5 m2/min. The microwave power dependence of the effective diffusivity coefficient followed an Arrhenius-type relationship. The activation energy for the moisture diffusion was determined to be 11.2 W/g. Increasing the microwave power resulted in a considerable increase in average energy efficiency and it was in the range of 8.8 to 39%.