In the classic Soleum, a steam generator is not required but is used 98% of the time! Most customers take a steam generator right away, because retrofitting is difficult and expensive.
In Soleum, all wall elements, seat and floor part are heated with special very powerful electric heating mats. These generate the pleasant radiant heat in the cabin. This is different from superheated steam, which provides the necessary temperature (~40-42°C) in a steam shower or steam room.