Energy consumption becomes a serious concern for manufacturing industry because it produces a huge amount of greenhouse gas emissions. Previous research has focused on the relationship between energy consumption and process conditions at the machine tool and spindle levels. However, little has been done to investigate the energy consumption in actual material removal at the process level. In this study, power profile and energy consumption at the process level as well as machine tool and spindle levels were characterized in hard milling. A new concept at the process level, net cutting specific energy, has been defined to investigate the energy consumed by the actual material removal. The relationship between cutting conditions and energy consumption at each level has been established. The results indicate that net cutting specific energy cannot be predicted by the traditional model. A new power regression model has been developed to predict net cutting specific energy at the process level.