Characterizing and modeling the energy consumption of machining processes has been recognized as an effective measure to improve the energy efficiency of the manufacturing process and to reduce carbon emissions. Activities related to machine tools and operators in machining processes result in energy consumption and carbon emissions. However, energy evaluation for the activities related to operators has often been ignored in the energy modeling of machining processes, due to its complexity and variability. Consequently, energy-saving strategies developed without considering the energy consumption of operators are not optimal. To bridge this gap, this paper develops an energy consumption evaluation method for the activities related to machine tools and operators, and establishes a novel energy model of machine-operator systems to assess the energy efficiency of machining processes. The research results provide a promising method to identify new energy-saving potentials of machine-operator systems. The recommended energy-saving strategy regarding this method is different to traditional strategies, but with it a better energy-saving effect can be achieved. Finally, a case study of energy modeling and analysis for a CK6153i CNC machine-operator system is examined, showing an energy saving potential of 15.85% and illustrating the effectiveness of the proposed method.