Use spray head type to determine gallons saved?

Is there a way to also provide gallons saved on top of time saved? I would think since you already know how much time is saved per zone from intelegent skips and in each zone you know available water rates based on spray head type selected or if its determined using advanced settings. Could you not utilize those values to also provide a rough estimate on gallons saved? Something easier to quantify cost savings than trying to use time saved.