This paper analyzes a power generation mix in 2040 with a model considering load-frequency control and reserves (corresponding to secondary control reserve or FRR). The current amount of renewable energy approved by FIT are unevenly distributed in Japan. If we assume that renewable energy will be expanding at the current growth rate, a total amount of renewable energy may be limited by the system constrains including control reserve and capacities of interconnection in the future. The results illustrate regional differences of 9 Electric Companies with respect to network configurations and power generation facilities. Local areas, which already have many renewable energy facilities, will reveal their limits to accept further renewable in their power system even with additional amounts of energy storage systems. In urban areas such as Tokyo Electric Power Co., there will be room for additional introductions of intermittent renewable energy. This paper also describes policy implications based on the analysis results. Future energy policies should consider projections of power system reserves and technological developments to encourage stakeholders to realize optimal power generation mix in order to achieve GHG emissions target of 2050.

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This study specifically analyzed changes in energy consumption per household during 1970–2016, presenting evidence that 1996 was the inflection point. In that year, the increase of residential energy consumption per household stopped. Subsequently, its value began to decline. From the following year, the relation of family size and per-capita energy consumption also changed. Energy usage for various applications also showed an inflection point around the same time. A statistical model created based on time-series data also strongly supports that conclusion. The collapse of the bubble economy was merely a trigger of the incident. Occurrence of an inflection point was unavoidable. However, the amount of decrease in energy usage thereafter was greater than predicted from the prior energy consumption structure. The protracted economic downturn raised public anxiety. Consequently, the rate of decrease in energy consumption grew. Effects of the aging population on energy consumption were also examined. Elderly people who lived in the 1970s tended to conserve energy more than young people because of their war experience. In other words, cohorts are important factors affecting energy consumption.

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