In this paper we evaluate the performance of Energy Management and Building Automation Systems in smart environment using wireless sensor network. We describe some aspects of smart grid and then explain the related communication models of smart meters and building management or energy management systems in a smart home. We propose three models, then we compare these models and we select a model for our test bed. We implement the selected model in real environment using wireless sensor network. We analyse network delay to find out whether wireless sensor network is useful or not. With proposed model, we can save up to 57% in energy cost. Also, we develop In- home display to inform customers about their energy usage so that they can manage their energy consumption easier.