In spite of recent successful demonstrations of flexible and transparent graphene heaters, the underlying heat-transfer mechanism is not understood due to the complexity of the heating system. Here, graphene/glass defoggers are fabricated and the dynamic response of the temperature as a function of input electrical power is measured. The graphene/glass defoggers reveal shorter response times than Cr/glass defoggers. Furthermore, the saturated temperature of the graphene/glass defoggers is higher than for Cr/glass defoggers at a given input electrical power. The observed dynamic response to temperature is well-fitted to the power-balance model. The response time of graphene/glass defogger is shorter by 44% than that of the Cr/glass defogger. The convective heat-transfer coefficient of graphene is 12.4 × 10−4 W cm−2 °C−1, similar to that of glass (11.1 × 10−4 W cm−2 °C−1) but smaller than that of chromium (17.1 × 10−4 W cm−2 °C−1). The graphene-based system reveals the lowest convective heat-transfer coefficient due to its ideal flat surface compared to its counterparts of carbon nanotubes (CNTs) and reduced graphene oxide (RGO)-based systems.