This book presents the proceedings of CPESE 2025, the 12th International Conference on Power and Energy Systems Engineering, to be held from 12 to 14 September, 2025 at Kyushu University, Fukuoka, Japan.This proceedings following a thorough peer-review process conducted in the light of originality, innovation, applicability, technical merit, organization and writing, and relevance to the conference by members of the technical committee. The papers included here cover a wide range Smart Grid, Renewable Energy, Energy Storage, Electric Vehicles, Power Electronics, Integrated Energy Systems, Distribution Networks and Motor System Modelling.This book will be of interest to all those working in the fields of Power and Energy Systems Engineering.