Abstract: An auxiliary heater device is for use with a primary room heater, the primary heater having a heating element cycling between operational and non-operational phases. The heater device includes a body configured to be disposed at least generally proximal to the primary heater, the body being either formed of a thermal retentive material or containing a quantity of thermal retentive material. As such, heat generated by the primary device is absorbed by the retentive material and subsequently emitted by the retentive material into a room so that the auxiliary heater device emits heat when the primary device is in a non-operational phase to reduce temperature fluctuations within the room. Preferably, the body is formed as an elongated tube disposeable upon an upper surface of the primary heater and the thermal retentive material is a semi-solid or gel disposed within the body tube.