The interest in Blockchain technology and its ability of creating consensus in decentralized networks is significantly increasing. This book provides a detailed consideration of the Blockchain technology and its possible implementations within the scope of energy management. Before investigating the functionality of a Blockchain, the basic mathematical problem that Blockchain solves, known as the Byzantine Generals Problem, is examined. Furthermore, this book describes the Ethereum platform, as most Blockchain energy applications are based on Smart Contracts stored in the Ethereum Blockchain. Afterwards, a descriptive insight into ongoing projects in the field of energy management is given. Conclusively, it is illustrated how a local peer-to-peer energy market can be implemented, based on the Ethereum Blockchain.