The development of "green" machine tools will require novel approaches for design, production and operation for energy savings and reduced environmental impact. We describe here work on three projects: i. influence of process parameters on power consumption of end-milling using force and process time models with experimental verification. Process parameters are chosen to minimize process time since power consumed by a machine tool is essentially independent of the load and energy per unit manufactured decreases with process time; ii. KERS (kinetic energy recovery system) for machine design and modeling the integration of a recovery system into a machine tool to calculate the amount of energy that could be recovered, and whether the environmental benefits are significant; and iii. evaluation of interoperability solutions, such as MTConnect, as tools enabling a standardized "plug-and-play" platform to integrate sensors with a unified monitoring scheme to achieve improved energy performance.