A ternary diagram is a graphical representation used for systems with three components. They are familiar to mineralogists (who typically use them to categorize varieties of solid solution minerals such as feldspar) but are not yet widely used in the physics community. Last year the lead author began using ternary diagrams in his introductory (calculus-based) physics course in a novel context--tracking the distribution of energy in a system as it transforms among three categories (e.g., gravitational, kinetic, and thermal) or transfers among three objects (e.g., inductor, capacitor, and resistor). The ternary diagram has some significant advantages over other graphical representations of energy distributions: an "entire scenario" can appear in a "single plot", even when using "very small time steps". This also means that the plot can be used to compare "relative rates of energy change" during various processes. Our goal for this paper is to introduce the ternary diagram and discuss these advantages in hopes that this will stimulate broader use of ternary diagrams and further research into their educational utility.