Abstract: A steam generator intended for intermittent operation has a cylindrical body in which a water-conducting passageway and hollow spaces for electric resistance elements are located. The cylindrical body is homogenous, and the water conducting passageway is located axially and symmetrically. From that passageway one or more radial passageways extend out of the body. The cylindrical body is externally provided with the heat insulating material, which in turn is enclosed in a casing of a material, at least the inner surface of which is reflective. An atomizer nozzle is located within the water conducting passageway, and is arranged to atomize water against substantially the entire wall surface of the passageway. The insulating material surrounds the body and has a thickness which is about equal to the radius of the cylindrical body. The insulating material and casing together maintain the body at a standby temperature of at least 70.degree. C.