The notion of essential orders was first introduced for the handling of decoupling problems. This paper focuses more on their interpretation, namely on the fact that each essential order corresponds to the highest time-differentiation order of a specific output appearing in the inverse model. During inverse modeling, this can in particular be useful for checking whether the specifications are appropriate to the structure of the given model. The aim of this paper is to define two procedures to graphically determine the essential orders directly from a bond graph (BG) model of a linear time-invariant system. Their usefulness is then justified in the context of a bond-graph based methodology for design problem analysis.