The purpose of this research is to show the optimal energy demand-supply systems of whole Japan considered the cities characteristic and district generators. The city in Japan is classified into four areas according to a size of population. The characteristic is given to the four areas using statistical data. Energy source, photovoltaic (PV) possibility, etc. by the each areas were clarified. Furthermore, the grid power system and the energy systems of non-industrial sectors were modeled by linear programming. Total expense for energy supply-demand is minimized under carbon-dioxide-emission restrictions. It was shown that the target value of carbon-dioxide-emission reduces 18% by optimized calculation compared with 2010. In the target case, 18 GW of CHPs were introduced on the large population area, and 108 GW (heat output capacity) of EHPs were introduced in all four areas. Introduced CHPs supplied 30 to 50% for the peak demand of electric power in the installed areas. EHPs and CHPs were introduced in all assumed scenarios, and it contributed to load leveling of the grid power system.

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With the introduction of the feed-in tariff (FIT) system in July 2012, there is a growing interest in expanding photovoltaic (PV) installations. The history of Germany and other countries, however, shows that a failure to adjust FIT prices promptly could result in a rush in installation, resulting in a huge policy cost. In particular, commercial rooftop PV systems are unique for their short lead time (about a couple of months) and a possible rapid decline in prices. Here we develop a simple model of the PV installation as a function of cost decline scenarios and FIT prices, and examine the effect of the time period for which the FIT price is updated. The more frequent the adjustment of FIT price is, the smaller the policy cost of unit installation. The rapid FIT adjustment can also reduce the uncertainty of the policy costs and PV installations. The law in the present presumes updating every year, or every six months in a special circumstance, although adjusting every one or two months is recommended. It does not explicitly recognize the category of commercial rooftop systems. A more adaptive policy framework is preferable, with frequent price adjustments and extensive price monitoring.

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The largest earthquake ever recorded in Japan struck on March 11, 2011 and measured 9.0 on the Richter scale. Furthermore, multiple nuclear power facilities were damaged by the earthquake. As a result, many people have been worried about power shortages during the summer and winter. The Japanese government and power companies appealed to people to conserve electricity and cut power use during peak hours. The Japanese people complied by diligently trying to conserve electricity. As a result, massive black outs were avoided in Japan. High temperatures were recorded in the summer of 2010. On the other hand, normal temperatures were recorded during the summer 2011. So, a scientific assessment of the energy demand is needed in considerations of the climate and other conditions. We are endeavoring to determine the appreciable post-quake amount of energy cuts. Final household energy demand models were generated by regions, energy types and seasons from data gathered from 2000 to 2010. The models number is 1504. This study revealed that the total annual energy demand dropped by only 1.2%. On the other hand, the annual electricity demand dropped by 6.2%. After the earthquake the electricity demand dropped by 9% in the summer, and by 0.6% in the winter but the demand for heating oil increased though out the year. Therefore, we consider that the heating oil increase was the cause for the majority of the drop in the demand of electricity. We will continue our search into the household energy demand area by area.

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