This paper proposes the PV-ESS system operation algorithm based on the weather forecast and load forecast. PV output is predicted using the weather forecast and the historical PV output data. The proposed ESS scheduling algorithm is developed considering the inherent forecasting error of PV output. To verify the proposed PV-ESS operation algorithm, a real time simulation environment, composed of RTDS, irradiation sensor, and temperature sensor, is developed. The simulation results showed the advantages of the proposed algorithm.