Industrial retrocommissioning (RCx) aims to improve the efficiency of existing mechanical systems without replacing major components. While RCx has typically focused on commercial buildings, the industrial sector also offers significant savings opportunities. Energy Trust of Oregon has successfully implemented RCx in the industrial sector, achieving over $162 million in annual energy savings. RCx in industry can optimize complex systems like compressed air, refrigeration, and central plants. Case studies demonstrate savings from simple measures like setpoint changes, equipment repairs, and control optimizations. Lessons indicate RCx is well-suited for high-tech industries and requires technical expertise to navigate complex industrial processes and systems.