Electrification of mobile working machines, such as excavators, wheel loaders and forestry ma-chines, presents new challenges in electric motor selection and sizing, particularly in handling peak loads and overload conditions. This thesis topic examines the peak load capacity and overload-based sizing of electric motors used in mobile machinery. The findings of this thesis should provide state-of-the-art for optimizing the selection of electric motors for mobile working machines. These insights contribute to the broader development of efficient and durable electrified work machinery.