Electric immersion heater for diesel exhaust fluid reservoir

An immersion heater including an encapsulated, semi-conductive, heating element. The heating element may be a non-metallic, carbon-based material in the form of a monofilament, a yarn or bundle of semi-conductive fibers which may be twisted, braided fibers or yarns, or the like. The encapsulation may be in the form of a tube of one or more layers of encapsulation material(s) with the heating element inserted therein. Alternately, the heating element may be thermoplastic with semi-conductive carbon additive, and the heating element may be coated with one or more external layers of insulating encapsulation material(s). The encapsulation material may be a rubber or thermoplastic material with sufficient chemical resistance to be immersed in a reservoir of fluid subject to freezing or thickening at low temperatures, such as DEF. The heater may be thermoformed into a predetermined fixed shape.