An electric motor includes a housing including a circumferential housing wall centered around a central axis, an annular stator fixedly mounted inside of the housing and including coils to generate a time-varying magnetic field, a busbar unit including a busbar holder and at least one busbar to electrically connect at least one coil of the stator to a power source to energize the at least one coil, and a rotor rotatably mounted inside of the housing to be rotated by an interaction with the magnetic field generated by the stator. The housing wall may include a housing wall engagement structure at an inner surface thereof engaged or configured to be engaged with a busbar unit engagement structure provided on the busbar unit. The housing wall engagement structure may include at least one protrusion defined by a portion of the housing wall dented into the interior of the housing.