This paper presents a study on the conceptualisations of energy systems which are used in computer modelling. A survey was designed and executed, containing questions about the type of energy systems, the scope of the problem, spatial and temporal dimensions of the work as well as software tools, specific conceptualisations and the difficulty of obtaining data. 50 responses were received, with people from a wide range of backgrounds and working on different types of problems. Key results show that almost all respondents use computer models and that the overall majority of them wrote or customised their own tools and models, which are generally complex and take weeks to months for a new user to become familiar with. More than two-thirds of the respondents claimed that it is either difficult or very difficult to collect the right data and a majority is willing to share input data as well as outcomes of the studies. However, only about half of them indicated that they currently use any shared conceptualisations or ontologies in their work. Analysis of the data reveals that researchers find data collection difficult in almost all circumstances and therefore if a common ontology facilitated easier data access, it could be widely applicable. From the results, we can confirm our hypothesis that there is not yet one widely used conceptualisation for energy systems, and it does not seem likely that a one-size-fits-all solution can be developed. Nevertheless the idea of a generic middle-layer ontology for energy systems, taking into account the standards that people already use in their work, could prove useful to link more detailed schemas and future work will explore how this can be achieved to benefit the larger community.