In the present flow system for a low dew point desiccant dehumidifier, multiple rotors have to be arranged in tandem.Because each rotor requires a regeneration heater, running costs of the system becomes large.In this work, we assessed and reviewed how to save energy in the low dew point dehumidifier.In the proposed energy saving flow, the regeneration heater for the first rotor can be removed by introducing the regeneration outlet air of the second rotor as the regeneration inlet air for the first rotor.The optimal rotational speed for the low dew point dehumidifier is decided as the highest efficiency point for using energy, and is expressed as nw.