has zero cloud cover and best for digitizing rooftops. This image was then georefred according to Google earth coordinates In Geographic coordinates system WGS84. ArcGIS 10.1 was used to Georef image. Google Earth imagery is used as a base map to digitize rooftops. The polygons were digitized at a zoom level of 1:250. Example of digitized rooftops is shown in Figure 3. Only a specific portion of rooftops is calculated. Not all the rooftop is digitized. Same size of area is selected from the houses of same size. Some Commercial buildings and school rooftop also digitized but a small portion not all available roof top. The mounts of rooftop are digitized so there is no shadow problem on selected area. Only roofs were selected for PV installation during digitization which meets the following criteria: As south, southeast and south west direction is best for PV installation, only buildings having required orientation were selected during digitization. There were no tilted roofs in study area. All buildings had flat surfaces, so orientation is not big issue for PV installation. No shaded rooftop area was selected in this study. All the selected roofs receive direct solar radiations. Rooftop areas shaded by other buildings, structures or vegetation that affected the solar yield were not included in the study. Those buildings having HVAC systems, air vents, chimneys etc., were not included in study area. No building had HVAC system nor chimneys etc. in study area. DEM data was not helpful for slope and aspect calculations. A survey was conducted to collect elevation data manually for a few rooftops. Garmin GPS was used to collect elevation data. This Elevation data was entered in rooftops. Average elevation was entered to rooftops other than surveyed. Then these polygons were converted to raster to using polygon to raster tool in ArcGIS toolbox using elevation data as a field. The survey was necessary to find out the average elevation of the study area for the calculation of annual incoming solar radiations. To understand geography, topography and rooftop shapes survey was conducted. During survey it was noticed that nearly all the roofs have mounts on their roofs. These are only for security purpose that no one can enter in the house from down stairs. These mounts do not have any other use. So these mounts were selected for the PV installation. The mounts same as shown in Figure 4, were selected during survey of the study area. Garmin GPS was used to find out elevation in the society. About 8 points were taken and average elevation was 202 Meters of study area. Forty bills were captured with a digital camera. As described above there are four types of houses in the study area having different sizes and different electricity load so it was necessary to collect data for all types. Raster made from survey data was used as input to calculate slope and aspect in ArcGIS. Slope and aspect tools were used in ArcGIS 10.1 tool box. The results were aspect and slope as a raster. The aspect was calculated clockwise from north 0˚ - 359.9˚ in degrees measured and was shown in Figure 5. While the inclination was calculated from 0˚ - 90˚ in degrees as shown in Figure 6. GIS model is a convenient way to generate solar radiation potential maps and there spatial relation to other data [19]. In this study, ESRI’s ArcGIS’s tool is used for GIS modeling in this study to calculate solar radiations. The main input for this tool is a Raster. This raster was made up of digitized roof polygons with average elevation as a field to convert it to raster using polygon to raster conversion tool from ArcGIS tool box. Electricity rate and bill data was collected from Lahore Electric Supply Company (LESCO) website. LESCO provides electricity to entire division as well as Lahore city.