The implication is that the NAV system is not worth the money if it is factory installed. However, since the TCH also includes the energy screen with minute by minute graphics of FE and the ability to look at FE over any period you want to test, that premise is invalid. I contend that I have increased my FE by at least 5% by using this screen. Over the life that I will keep the TCH, that will more than offset depreciation of the NAV system with fuel savings.