Energy flow diagrams in the form of Sankey diagrams have been identified as a useful tool in energy management and performance improvement. However there is a lack of understanding on how such diagrams should be designed and developed for different applications and objectives. At the national level, a framework matching features of Sankey diagrams with various objectives of energy performance management provides better understanding how Sankey diagrams can be designed. As part of the framework, boundaries outlined around a group of facilities provide a refined representation of sub-systems that trace energy use in various conversion devices, products and services, which identifies potential areas for energy savings. There are some differences between energy flows and exergy flows represented in Sankey diagrams. Furthermore, exergy flow Sankey diagrams offer advantages in identifying potential areas for energy savings. This is illustrated at a national level, using UK's industrial heating processes that overlays both energy and exergy flow diagrams. (C) 2014 Elsevier Ltd. All rights reserved.