Even before the 2011 release of the ISO 50001 energy management standard, which lists Sankey diagrams as one tool for energy analysis, companies and consultants have been using them in energy efficiency and energy management projects. Many published examples come from Austria, like this one.
Below is a Sankey diagram example for Austrian company ‘Joh. Pengg AG’ from a 2005 report published by Austrian Federal Ministry for Traffic, Innvation and Technology (bmvt): (H. Bayer: ‘Abwärmenutzung und Einsatz Erneuerbarer Energieträger in einem metallverarbeitenden Betrieb’, Report in German, Sankey diagram on p. 34).
All flows in kWh, total energy consumption for the year 2003 is 45,35 Mio. kWh. The red flows are for electric energy, the yellow ones for energy from natural gas. The middle column has the different equipments that consume energy within the company. Useful energy quantities (“Genutzte Energie”) are shown in orange, while losses are outputs in pink that are visually “collected” and joined again in the last node. Not sure what the light blue part stands for.