A sub-kilogram scale (∼500 g) of expanded graphite nanoplatelet (EGnP) with multi-layered graphene sheets were successfully fabricated using a simple mild-oxidation of pristine graphite. In particular, a substantial amount of trapped water molecules in EGnP make it a good ionic conductor, while simultaneously allowing it to serve as an electrolyte with ion transport characteristics. Due to its high electrical and thermal conductivity, micro-patterned EGnP can be used to produce electro-heating elements for line heaters. We found that the surface resistance of EGnP-based films was two orders of magnitude smaller than that of graphene-based thin films. The EGnP-based line heater demonstrated efficient heat propagation with uniform temperature distribution, resulting in an energy savings of up to ca. 37% in comparison to the graphene-based flexible heater. Especially, the steady-state temperature increased as the applied voltage increased and it reached to 172.3 °C at a driving voltage of 14 V. In addition, the EGnP-based line heaters under a bending radius of 4 cm had a 25 °C higher temperature as compared with heaters under flat conditions. Most of all, screen printing technique provides the facile formation of shape and size, and makes it possible to be used as a cheap and lightweight patch heater for industrial applications.