Out of all the popular cities in Germany, Mannheim is the cheapest city to rent a car in at just $14/day. Renting a car in Mannheim is 30% cheaper than renting one in Cologne where the per day rate is around $20. Other fairly inexpensive cities in Germany to get a rental car in are: Paderborn ($15/day), Hannover ($15/day), and Aachen ($16/day). While these cities typically have cheaper prices than the rest of the country, travelers looking to rent a car in Berlin should expect to spend around $18/day on their transportation. The most popular city to rent a car in Germany is Berlin.