This work considers a hydronic radiative cooling (RC) panel to be coupled with a phase change material (PCM) storage tank system to assist a conventional air conditioning (AC) unit in meeting the cooling needs of an office space during occupancy hours. The nocturnal radiative cooling power is used to regenerate the PCM during nighttime and the diurnal radiative power is used to pre-cool the air supplied to the condenser of the AC unit during daytime to enhance its performance. A mathematical model is developed to predict the system operation; it integrates the hydronic RC panel model, water/PCM system heat exchange model and space model. The developed model is applied to a case study considering an office space located in Kuwait. An energy analysis is conducted to predict the energy savings of the proposed system in comparison to typical AC system, for the months of June, July, August and September. Results show that the use of the diurnal cooling power of the RC panel was able to enhance the coefficient of performance (COP) of the AC system. Moreover, a reduction in the energy consumption of the AC unit of 37.74% during the four considered months was achieved.