Evaporative cooler is an old recognized technology for air conditioning. This system is used in the most areas of the world which have hot and dry weather. The evaporative coolers used today, have the design related to almost fifty years ago, and it makes the sense of wonder as their design has not been changed during these years. Due to several problems existing in such coolers they have not enough efficiency in the hot weather of summer. In this research performance and problems of these coolers have been discussed and for increasing the efficiency and cooling power of them a new design has been presented. One of the major problems of a evaporative cooler is low speed of evaporation on the surface; in the new design presented in this research the speed of evaporation has been significantly increased by spraying the water on the air inside the cooler. The theory of the new design included the evaluation of water evaporation kinetic and comparison of it between bulk and droplet forms. The impact of droplet form of water on evaporation, condensation and vapor pressure has been discussed. Afterward production of new designed cooler has been done. Moreover for estimating the cooling efficiency of the normal water cooler and the new designed one an experiment was arranged to measure the temperature and humidity of the outgoing air form two coolers in the same situation. Cooling efficiency of the common cooler is around 60-70% while the new designed cooler has 95% efficiency. Therefore, the new designed cooler increases the cooling efficiency of common coolers around 30-40% It means the new designed cooler improves the cooling property almost 5-6 Centigrade degrees. Comparison between two coolers shows the superiority of the new designed one over the common one. This superiority is in the more cooling efficiency and the less power consumption. Considering the significant numbers of evaporative cooler used in Iran, if the old designed coolers replaced by the new designed one there will be a considerable saving in the power consumption. This saving will be on summer which is the peak of power consumption and there will be a direct effect on the water reservoir of the country.