The challenge is to identify cost-efficient measures for decreasing the energy demand at a reasonable effort in existing production sites. Metal cutting machine tools should be an integral part of investigations in the course of energy efficiency optimizations. This paper expands existing approaches for the rapid identification of energy efficiency potentials. Since most of the energy demand of machine tools is emitted as waste heat, the paper also focuses on how this influences central cooling systems. In addition, the authors have measured, analyzed and evaluated several metal cutting machine tools in a case study and planned corresponding retrofits.