This paper evaluates the potential of Quaid-e-Azam Solar Park (QASP), Pakistan and examines its impact on distribution networks. To estimate the PV plant yields, solar park's historical hourly weather data from the years 2000 - 2014 is used. For handling of such huge data, the yearly data is partitioned into four seasons. Further, the seasonal data is modelled by using Beta Probability Density Function (PDF) and a 24 hour solar curve for each season is generated. The solar farm power outputs are tested in IEEE 33 bus distribution network by using time-varying seasonal hourly loads, meanwhile system losses and bus voltages are calculated. The results show that with the passage of time, the impact of solar PV power on reduction of system losses gradually decrease due to yearly degradation of PV module efficiency. System losses at end of PV farm life are 10 - 12 higher than those losses as in the first year. Furthermore, low voltage buses also pose to risk as system voltages also start to decrease. From the analysis, it is suggested that for maintaining the quality of network, time varying detailed assessments should be performed during the calculations of sizing of distributed generation. © 2018 The Authors, published by EDP Sciences.