Energy and exergy study of an air-water combined solar collector, which is called dual purpose solar collector, is investigated. The method of epsilon - NTU is used. Analysis is performed for three air passages of triangle-, rectangular-, and common-shaped channels. Parameters like the air flow rate and water inlet temperature are studied. Results show that a dual purpose solar collector has better energy and exergy efficiency than a single collector. In addition, the triangle passage with a water inlet temperature of 60 degrees C has shown better exergy and energy efficiency than others.