The electrical grid evolved markedly over the past years and new Smart Grid phenomenon was born. Many new technological trends and concepts were introduced including also the blockchain. In the recent years, many theoretical ideas of using blockchain in Smart Grid were discussed, which resulted in new start-ups and test pilots deployed. This paper focuses on the investigation of peer-to-peer blockchain based energy trading suitability. We offer more broad discussion on the challenges and issues related with the selected application, which should help to understand the relations between application levels.