This thesis work verifies the alternative use of solar energy to be applicable in Addis Ababa at the selected site, Gerji Condominiums. Selection of the Flat Plate Solar Collector and its area, studying the unit cost of solar water heater and orientation of individual houses, determination of number of collectors, and their cost analysis are conducted. The meteorological data governing the global radiation and monthly sunshine hours was used. Based on the annual solar energy availability as well as the hot water demand; the solar energy unit price and the payback period were calculated. AutoCAD and ArchiCAD have been used to identify the orientation and the integration of the block with the collector’s respectively. Energy consumption has been saved due to the replacement of solar energy by electricity; monthly energy expense would be minimized by around 5% in comparison with electricity by an amount 0.273birr/kwh i.e unit price of solar energy is half of electricity. Therefore, using solar energy as an alternative source of renewable energy for the selected site is the reliable solution.