Abstract: A dishwasher which generates steam from the surface of a body of water in the dishwasher tub, without substantial heating of the entire body of water, during at least parts of the washing and rinsing operations performed on dishes within the tub. Heating only a surface layer of the body of water to generate steam results in substantial energy savings, particularly when the dishwasher is supplied with cold water, instead of preheated water. Efficient steam generation, and heating limited to the surface layer of the body of water, are achieved by utilizing a large-area partially-submerged electric heater, comprising an electrical resistance heating element carrying a heat conductive, metallic jacket of enlarged cross section. The jacket is provided with a depending peripheral skirt for trapping air and/or steam beneath the jacket so as to minimize downward heat transfer from the jacket to the water below the surface layer.