In this work, we have studied the characteristics of a heater based on single-layer graphene obtained by CVD using methane as the carbon precursor and using copper as a catalytic substrate. Synthesized graphene was transferred onto an EVA/PET substrate using a heat press printing method. A theoretical model of heating a polycrystalline graphene film was developed. The temperature gradients in graphene crystallites were estimated based on the model. It was shown that local overheating of graphene crystallite boundaries is the main cause of damage for the graphene-based heater. In order to enhance the power of graphene heaters, it is necessary to reduce the size of 2D graphene crystallites that make up the coating.