Economical, environmental and legislative drivers have recently raised the awareness of energy consumption and the associated environmental impact of manufacturing processes. A reliable prediction of unit process energy consumption will enable industry to develop potential energy saving strategies during product design and process planning stages. This paper presents an empirical model to characterize the relationship between energy consumption and process variables for material removal processes. The methodology has been tested and validated on a number of turning and milling machine tools. The model presented predicts the energy consumption of manufacturing processes with an accuracy of more than 90%.