This book constitutes the refereed post-conference proceedings of the 6^th EAI International Conference on Green Energy and Networking, GreeNets 2019, held in Dalian, China, May 5, 2019. The 30 full papers were selected form 44 submissions and cover a wide spectrum of ideas to reduce the impact of the climate change, while maintaining social prosperity. In this context, growing global concern leads to the adoption of the new technological paradigms, especially for the operation of future smart cities.