The residual demand, which is defined as electricity demand minus power supply from variational generators, is getting important to be considered as installations of variational generators to power grid systems are increasing. Because variational power generations and electricity demand fluctuate due to variations in weather, the residual demand is supposed to be influenced by weather variations. However, understanding of the variability of the residual demand is not deepened adequately. Therefore, we investigated variability of the residual demand to deepen understanding of the mechanism for how meteorological variability of photovoltaic (PV) power generating systems affects the variability of the residual demand. Because there is not enough long observation data to analyze the variability of residual demand and power supply from PV systems, numerical simulations were performed using numerical models of electricity demands and PV systems. Local and seasonal characteristics of variations in the residual demand are generated by variations in the electricity demand and power supply from PV systems and the correlation between the electricity demand and power supply from PV systems. It was an interesting finding that installation of PV systems causes reduction of variability of the residual demand depending on some situations of areas and seasons.
