Currently offered satellite navigation systems for cars are primarily focused on selecting the route with the shortest travel time. These systems also feature relatively simple models that allow the selection of the route with regard to minimizing fuel or electricity consumption, usually called the most ecological. Their effective use requires users to define basic vehicle data, such as drive type, maximum speed, etc. The paper presents an analysis of the impact of selected parameters characterizing vehicle properties and traffic conditions on energy consumption. The focus is mainly on parameters that can be technically used in car navigation systems to plan energy-saving routes. The analysis uses routes recorded in real traffic. The results of these analyses allowed the development of several guidelines for planning routes taking into account the EEC minimization criterion. One of the observations is that for roads with large changes in road height (over 20 m/1 km of route), a flat route with a length increased by 50%, may be more energy-efficient than the original one. This is due to the efficiency of the regenerative braking system being significantly lower than 100%.