With the increase of public programs to encourage the use of electric vehicles and the shift of social reception towards so called energy efficient solutions the research in the field of vehicle routing using low-emission vehicles has increased as well. We therefore introduce a new problem, the so-called Electric Fleet Size and Mix Vehicle Routing Problem with Time Windows (EFSMVRPTW). The problem covers real world applications where an optimal mix of different available battery powered (and conventional) vehicles has to be found.