  Peer-to-peer trading is a next-generation energy management technique that
economically benefits proactive consumers (prosumers) transacting their energy
as goods and services. At the same time, peer-to-peer energy trading is also
expected to help the grid by reducing peak demand, lowering reserve
requirements, and curtailing network loss. However, large-scale deployment of
peer-to-peer trading in electricity networks poses a number of challenges in
modeling transactions in both the virtual and physical layers of the network.
As such, this article provides a comprehensive review of the state-of-the-art
in research on peer-to-peer energy trading techniques. By doing so, we provide
an overview of the key features of peer-to-peer trading and its benefits of
relevance to the grid and prosumers. Then, we systematically classify the
existing research in terms of the challenges that the studies address in the
virtual and the physical layers. We then further identify and discuss those
technical approaches that have been extensively used to address the challenges
in peer-to-peer transactions. Finally, the paper is concluded with potential
future research directions.
