Why and how your country is using one particular (most important or interesting source of renewable energy to generate electricity? In Iran, the hydroelectric power is more used than the other renewable resources. Iran attempt to construct the barriers on rivers to produce the electricity, because the affluent of rain in Highland, high Debbie rivers in these areasand being the permanent water. What are the biggest potentials concerning renewable energy production in Iran and what obstacles hinder a higher degree of their use now or in the future? Iran has the high potential to gain the solar, wind, water power and geothermal energies because it is located in low latitude, in earthquake and igneous activities belt path, in airflow path, blowing of local wind, having the watery rivers in mountainous area. Unfortunately, it is paid little attention to renewable energies becauseIran has high oil and gas reserves (Iran has the third rank in oil resources and second rank in gas resources). Main obstacles for using of renewable energies are the high costs of investment; so that cost of supply in some cases is around double than fossil fuels. For this reason, private sectors don’t have interest to investment in renewable energies in spite of government policy for encouraging in this area. So, lack of sufficient financial supports are very problematic to implement of renewable energies in Iran.