Sustainable energy management systems continue to evolve, adding layers of complexity and functionality. The paper presents an innovative approach that deals with the application of complex systems formalism and contemporary knowledge management techniques for the purposes of assuring more effective delivery of sustainable energy schemes. Knowledge-Managed Sustainable Energy (KMSE) systems leverage energy knowledge assets optimally, and with greater flexibility, to enhance energy management performance. The KMSE scheme developed adopts a multi-factorial approach for sustainable energy-related knowledge acquisition, aggregation and diffusion, within managed environments. The paper presents a structured framework for developing effective KMSE systems, and discusses their applicability to a range of renewable energy management projects, with the ultimate aim of fostering continuous energy management performance improvement and sustainability.