Solar energy is a free, accessible and pollution-free resource which can be used as an alternative to fossil fuels in the current climate of Iran. The purpose of this study is to estimate the spatial and temporal distribution of solar energy with emphasis on plains of Iran. For this purpose, cloud cover amount and sunny hours during the period of 30 (1985-2014), 20 (1995-2014) and 10 years (2005-2014) for 51, 146 and 218 synoptic stations of I. R. of Iranian Meteorological Organization have been derived respectively. Then the day light hours for 403 stations were estimated monthly and annually and were zoned using GIS. Both of monthly average of cloud cover amount and sunny hours have been derived during warm seasons (March to August) and cold seasons (September to February). The cloud amount have been classified in the following three classes; clear to partly cloudy (0-2 Octa), semi cloudy (3-6 Octa), and total cloudy (7-8 Octa). The results showed only clear and partly cloudy during May through September and Semi-cloudy region were shown during October through February mostly occurred over Northern regions, Caspian coast, and North West of Iran. The Maximum of monthly sunny hours has been occurred in Mashad station with 15.7 days in June and the minimum in Anzali station with 3.8 days during 30 years. The results of the study of the three average parameters of amount of cloud cover, sunny hours and day light hours show that the greatest potential for solar energy utilization is in the summer and then in the spring. Spatially, this potential is observed in the plains of semi-southeastern and eastern, central and southwestern regions of Iran, respectively. In addition, all temporal and spatial changes of these three parameters are directly related to the climate systems of Iran and the position of the sun.