Sankey diagrams are typically used to visualize energy or material or cost transfers between processes. They can also visualize the energy accounts, material flow accounts on a regional or national level, and also the breakdown of cost of item or services.
Sankey diagrams put a visual emphasis on the major transfers or flows within a system. They are helpful in locating dominant contributions to an overall flow. Often, Sankey diagrams show conserved quantities within defined system boundaries.