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. 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/-