In the present globally interconnected world, energy is generated, stored, transmitted and consumed and its related waste disposed of or recycled- through a complex and dynamic system of systems. A central challenge for Global Systems Science is to focus on the multiple interactions of different scales of the energy systems: from smart micro-grids to super grids. To what extent can these two approaches coexist? How do these two apparently divergent trends and configurations relate to each other and can be managed for a better coordination and efficiency? Global Systems Science should be able to identify what kinds of factors are most relevant for the global energy systems and to what particular pressures are they more sensitive (e.g. not necessarily prices but perhaps to other variables outside the energy systems). This report presents the key points and open issues in emerging energy systems and highlights questions and challenges to global systems science applied to energy systems. It is based on the discussions and results of the workshop on "Vision in global systems science: energy futures" held in Brussels on 18th and 19th March 2013 and organized by DG Connect in collaboration with Joint Research Centre, Institute for Energy and Transport, Petten.