An impeller pump has a pump casing including a pump chamber and an inlet and an outlet thereon and an impeller therein, and including a heating device for heating the conveyed medium, which heating device forms an external wall of the pump chamber. The pump chamber extends annularly around the impeller and away from the pump chamber floor, wherein the outlet leads off on a region of the pump chamber which, viewed in the axial direction of the impeller pump, is pointing away from the pump chamber floor. The cross-sectional area of the pump chamber decreases in the axial direction of the longitudinal center axis of the impeller pump away from the pump chamber floor toward the outlet by virtue of an obliquely inwardly inclined external wall.