The energy consumption during granulation process in horizontal drum granulators at variable process and equipment parameters: drum diameter, angular velocity and the degree of drum filling with raw material was investigated. The feed was wetted drop-wise during tumbling at a constant liquid flow rate. During the whole process the instantaneous values of the driving torque on the shaft were measured. The effect of the drum diameter, its angular velocity, drum filling degree and moisture content of the feed on energy consumption was evaluated. A model of the dependence of energy needed for nucleation and granules growth during wet granulation for different process and equipment parameters was proposed in the paper.