Blockchain is a powerful technology to facilitate decarbonization, decentralization, digitalization, and democratization (4D's) of the energy systems of the future. The 4D's are the driving forces of transition into new energy systems that are more sustainable, resilient, efficient, and equitable. Although this technology can be applied to a wide spectrum of applications in the power sector, a set of challenges and limitations still need to be addressed to facilitate a full‐scope implementation in energy systems. This paper presents an overview of blockchain technology from its inception through its most recent evolution and presents a thematic review of state of the art in the application of this technology in power systems. Further, it addresses the barriers preventing the power sector from large‐scale, full‐scope adoption of this technology. Finally, the emerging blockchain trends in the near future will be discussed and its potential to facilitate a secure, decentralized energy trading platform will be investigated.