Question:What is a Sankey Diagram?
A Sankey Diagram is a way of showing how the energy supplied to something is used.
Please look at the Sankey diagram for a light bulb below.
All of the energy put into the device is represented by the thickness of the arrow at the left.
The width of the arrow is then divided into however many parts are needed to show what happens to all of the energy.
In this case all of the energy is used to either produce light with is useful or is converted to heat which is not useful or wasted energy.
Note: You do not need to put the useful energy at the top or the biggest arrow at the top, but one of these is most often done.