Electric: The modern style of kotatsu, oki-gotatsu (置き炬燵), consists of a table with an electric heater attached to the underside of the table. This evolved from a clay pot with hot coals placed under a table.[1] The kotatsu usually is set on a thin futon, like a throw rug. A second, thicker futon is placed over the kotatsu table, above which the tabletop is placed.