It is well known and taken for granted that the efficiency of energy use by comminution (i.e. breaking, crushing, grinding) equipment is very low, typically less than 10%. Most of the process input power is dissipated as heat and noise and ineffective deformation of the material to be processed and the device itself. Here, a study is reported that analyses the reasons for this low efficiency and tries to give recommendations for improvement. With a lab-scale jaw crusher as a test case, an optimisation was made on how to operate it most energy-efficiently by using an evolutionary algorithm numerical method. For a selected optimised case an attempt was made to simulate the jaw crusher using a commercial software for discrete element modelling (DEM), after first simulating single particle breakage using this software. Also, some experimental results on the crushing of several similar to 600 g pieces of rock while measuring electric power during the process are reported. (C) 2014 Elsevier Ltd. All rights reserved.