Indonesia is a country that has a tropical climate with an average daily irradiation value of 4.8 kWh/m2. In general, the large potential of solar energy in Indonesia is the main capital as a source of energy that can support electricity energy security. However, the problem faced in planning the solar panel plant (SPP) is efficiency factor which is closely related to the amount of daily irradiation that can be converted into electrical energy optimally. This study investigates characteristics of solar radiation as preliminary analysis for solar power plant construction planning at PLN Institute of Technology. For this purpose, quadratic regression model is used for prediction using data solar radiation between 8 AM to 4 PM. Main result shown that applied model can provide the characteristics of solar irradiation in a day at observed place with a correlation level is 0.9288 (R = 0.9288) and obtained Mean Absolute Percentage Error (MAPE) is 18.6% (accurate is 81.4%). Presented information can be used as a basic reference in planning SPP development at PLN Institute of Technology.