SUMMARYIn the past, we have proposed battery operations in a photovoltaic (PV) system using PV output and load power forecasts. In the proposed method, we utilized multiobjective optimization for a residential area model that includes a large number of PV systems with storage batteries. To practically demonstrate that the proposed operation effectively improves economic and environmental efficiency, it is indispensable to evaluate the effects of forecast error on the operation design of a PV system with storage battery. In this paper, we propose a method for evaluating the robustness of battery operation taking account of the statistical characteristics of forecast errors. Some numerical examples, which show the validity of the proposed method, are also presented.