In this review, an energy-saving device is brought into the air-handling unit (AHU). Because of increases in energy costs, energy saving devices or systems have become the new favored pattern in tropical nations. An essential cooling coil framework is consolidated into the AHU to recycle the condensate water to accomplish energy savings. The warm external fresh air is drawn through the essential cooling coil to recover the idle heat of condensate water. The enormous temperature slope between the warm fresh air and condensate water augments the measure of energy recovered.