Since emulsification for the production of O/W emulsions is a process associated with a gain in interfacial energy, its energy efficiency was defined as the ratio between the interfacial energy acquired and the energy consumed during emulsification. The energy efficiency thus defined could then be comprehensively correlated with the energy consumed by three different emulsification processes, - rotor-stator homogenization, high-pressure homogenization, and membrane emulsification. This correlation suggests that membrane emulsification resembles a high-pressure process from the viewpoint of energy consumption.