To investigate energy distribution and transfer during mechanical coating and ball milling, mechanical coating of Cu coatings on Al2O3 balls and a series of contrast experiments were performed by a commercial planetary ball mill. After a stable heat and energy state of the system was set up, the input electric power and temperature of the bowl's outer wall were measured. The distribution of electric power consumption in the system was established. The kinetic energy utilization efficiency of the electric motor was obtained for the first time to be 72.8%, 74.7% and 81.0% at the rotation speed of 400, 480 and 560 rpm, respectively. The transferred energies by Al2O3 balls of unit weight in unit time or by one Al2O3 ball during each collision were calculated to be in the order of 10(-1) J . g(-1). s(-1) and 10(-5) J, respectively. Due to Cu powder addition, the transfer ratio of the kinetic energy of Al2O3 balls during collision was greatly increased from 22-40% to 78-84%. The collision between Al2O3 balls and the inner wall of the bowl also got close to perfectly inelastic collision. (C) 2013 Elsevier B.V. All rights reserved.