This study presents a GIS-based model to identify optimal sites to install large-scale smart grid-connected Photovoltaic (PV) power plants. Input datasets include digital elevation model, road networks, grid lines and daily average solar radiation. Using multi-criteria decision-making approach, we set constraining conditions for slope, proximity to the road, proximity to grid lines, solar radiation and land use to optimize the process of selecting suitable sites. Also, we predicted energy generation potential, installation capacity and CO 2 emission reduction potential. The result shows that 790.48 km 2 (40%) of the study is optimal for large-scale PV installation. Furthermore, a total of 105276.88 GWh/yr annual electricity generation, 59.29 GW installation capacity and yearly CO 2 emission reduction of 66324 (kt-CO 2 /yr) are estimated for Selangor. This study indicates that based on the 2030 national energy demand, about 38.4% of the annual energy demand could be met if 59.29 GW capacity is install in Selangor. Similarly, the study predicts 13.2% annual carbon emission reduction offset from the predicted 2020 CO 2 emission.