It is essential to understand in which way and how much energy is transferred from the milling tools to the powder in the milling process. We have attempted to quantify the energy transferred per impact and per unit of mass in a planetary mill assuming that collision is the dominant energy transfer event. Further, attrition mechanism (rolling/sliding) has been considered by evaluating the effect of filling the milling vessel. The energy transfers evaluated by the above modelization have been proved to be able to correlate the input energy and the different solid state reaction undergone by the Pd–Si system submitted to the milling action in both planetary and shaker mills. Measurements of power consumption during the milling process have been also performed and compared with those based on theoretical modelization. The fairly good agreement obtained gives a strong support to the validity of the theoretical background.