The use of renewable energy,such as from photovoltaic (PV)systems,is expected to provide an effective means for reducing the dependence of households on commercial electricity supply. However, because of mismatch of the power supply and consumption of electricity, surplus electricity generated by PV systems is fed into the commercial power grid. With the increasingly widespread adoption of PV systems, this approach may introduceinstability to the grid in the near future. In this context, using batteries to store surplus electricity may be effective for reducing the amount of surplus electricity flowing into the commercial power grid.In this study, we evaluated the load leveling effect of using electric vehicle batteries as a storage system for surplus electric power generated by PV systems installed on single-family houses in cities in Japan.