The smart concept has changed both household electrical systems (smart home) and the whole electric power system (smart grid). It has facilitated much more efficient electrical energy management. Therefore, there is a need to develop a detailed model and knowledge base at the micro-system level, which can respond to changes in the electric power system. Extensive knowledge (know-how), large financial outlays, and access to modern technologies are necessary in order to design and build a functional smart grid. The first installations were made in highly developed countries. Currently, a significant proportion of newly built power installations in Europe have the features of a smart grid type. Developing countries, such as Poland, should benefit from the experience of other countries in the process of building modern installations. The article addresses the energy performance of a household and the ontology of a household micro-system, while taking into account the possibility of it being controlled via energy management systems (EMS).