Energy efficiency is crucial for reducing the climate footprint, enhancing green transformation and improving the economy and energy resilience. This paper aims to identify and demonstrate gaps between industrial practices found in empirical case studies and academic knowledge of industrial best practices for energy-efficient manufacturing design. The paper uses empirical cases where environmental and energy-value stream mapping and Green Kaizen tools were used to analyse production operations, highlighting potential operational and design improvements in production equipment and systems, and showing there are still large opportunities for energy efficiency improvements in manufacturing operations, which can save money and reduce environmental impact. Yet, several inefficiencies are determined in the equipment and production system's design phase, which are challenging to change once the equipment is in operation. The secondary climate effect of energy savings in a Swedish context, where unused electricity can replace fossil-based electricity, is discussed. The paper contributes to theory by linking previous research findings with the current industrial challenges and opportunities for energy and sustainability in operations management. The paper provides results and knowledge to help the industry improve energy efficiency in production.