Embodiments of the invention provide an LED replacement light assembly for retrofitting an incandescent light fixture that has a housing with a base. The LED replacement light assembly can include a shaft with a top portion and a lower threaded portion. The lower threaded portion can be screwed into the base. The LED replacement light assembly can also include an LED adapter, and a circuit board including a plurality of LEDs. One embodiment can include a thermally conductive disc that can engage the circuit board and the housing to conduct heat from the circuit board to the housing. A thermal interface can be positioned between the thermally conductive disc and the housing to provide enhanced conduction.