Economic analysis of Hot Water Supply Using Solar Energy(Case study of a residential buildings in Tehran)

In this study, inflation and time value has been taken into account for the economical investigation of the period of return on investment in replacing natural gas water heaters in Tehran residential buildings. First economic analysis was calculated considering all replacing cost by the residents. Second, the calculation was done if the government through the Ministry of Energy pays for all replacing cost. After reviewing of various strategic of replacing natural gas boilers with solar water heaters considering the importance of economic and environmental subjects, replacing by citizens because of the financial problems and a long period of return on investment (12 years) is impossible. On the other hand due to reduction of air pollution and greenhouse gas emissions, especially CO2, and the country's ability to exporting natural gas to neighboring countries, the strategy of subsidize of replacing by the Ministry of Energy has a return on investment (in first year) is much more reasonable.