Sustainability is a critical topic and needs to be systematically integrated in engineering education and professional training courses in manufacturing organisations. Eco-efficiency is a key sustainability concept but it can be challenging to teach as it is highly practical and thus ill-fitted for purely classroom environments. Games and simulations provide a good mechanism for effective and engaging teaching on such practical topics. This paper describes a case study of four game sessions ran in a manufacturing company. This empirical research shows how the card game ‘One thousand kWh’ enabled participants to actively learn about energy efficiency in manufacturing operations, and to explore sustainable manufacturing practices and barriers to implementation.