Power operated onion detopper-cum-grader was developed which consist of feeding mechanism, power operated onion detopper and grading mechanism.Onions after detopping are graded in five grades i.e. <35>85 mm. The field performance of power operated onion detopper-cum-grader indicated that the average detopping efficiency was 85.71% with 237.192 kg h-1 output capacity. The average feeding rate was found to be 276.856 kg h-1 and the average time required for detopping was 0.421 h q-1. The average power requirement at load was found to be 0.880 Kwh-1. The average onion neck length before and after detopping was 314.8 mm and 23.433 mm respectively.Net saving by using power operated onion detopper-cum-grader over manually detopping and grading was Rs 55.67 per quintal. Automatic detopping and grading is done simultaneously by this machine. The total cost of power operated onion detopper-cum-grader is Rs 85900/-