Decentralising the power systems management brings clear advantages for the grid and for the stakeholders (consumers, generators, operational and management actors). The grid decentralisation can be achieved using microgrids. Some microgrids emerge worldwide, working as small energy islands. It is admitted that ontologies and open (Semantic) Web standards can form a basis for advanced communication architectures in smart grids. True, ontologies enable semantic interoperability and logical reasoning; the Linked Data principles enable the discovery of new information on the web. This paper reports on the use of these formalisms and principles to develop a new information system for a microgrid site already in place. More specifically, we developed a new ontology to represent time series of multiple observations, and made real-time consumption data available on the web as Linked Data. This enables consumption reporting, and enables other researchers to test their algorithms against real-time consumption data.