"An electric stovetop is about 70 percent efficient, although that varies widely depending on the type of pot or kettle you use. Most of the energy is lost heating the air around the stove.
An electric teakettle is about 80 percent efficient, although again this varies from kettle to kettle. Electric kettles are generally very well insulated, and the heating coils sit directly in the water, so less heat is lost to the air.
An induction stove or hot plate is about 85 percent efficient. It creates an electromagnetic current directly in a pot to generate heat, losing very little to the air."
[as a footnote, the above apparently implies that kettles are not necessarily induction, and of course there are stovetops that are induction]
