Price rising of energy and the limitation of fossil fuel makes it an inevitable tendency to introduce distributed energy such as renewable energy to the existing supply system in the future. Different players, such as power generation, transmission, and distribution, along with the value chain must now cooperate and interact with each other by shared interfaces or eventually a customized network for secure and reliable delivery of energy. While smart grids are focusing on the informationization and intellectualization of the existing power grid, the new concept of an energy internet is proposed as an internet-style solution for energy issues by integrating information and power flows bi-directionally, which can be considered as the version 2.0 of smart grids. Some key features of an energy internet compared with conventional energy grid such as openness and peer-to-peer are introduced. Architecture of an energy internet is proposed in details, including energy storage, switches and routers. The definition of an energy internet call for a much greater degree of interactive flexibility for efficient energy management than the present system is designed to handle.