A navigation device has an evaluation unit for determining a maximal range, which can be traveled in the current driving operation mode with an amount of energy stored in an energy storage device of the motor vehicle, and a display unit for displaying a road map, on which a border of an action field delimited by the determined at least one maximum range is presented. A range indicator can be adapted with low expenditure to different types of road maps. On the basis of the graphic data of the road map to be indicated, a graphic processing unit produces a representation of the road map with a region that is offset in terms of height in relation to a map plane. An extension of a border of the region that is offset in terms of height corresponds to the extension of the border of the action field.