The March 11, 2011 disaster created the need to review Japan’s energy architecture. We believe that it will take about 10 years for Japan to fully decide on a new energy and electricity architecture, and it will take about 3 years to reach decisions on the future of Japan’s nuclear power generation. Japan has taken a careful approach towards the development of renewable power, and renewable power - except for hydropower - is substantially lower than in most other advanced countries. Japan’s potential for renewable energy is very high, especially wind and geo-thermal power, and will required substantial changes in laws and regulations, and a decentralized and democratic approach to grid management. Necessary liberalization of Japan’s electricity markets is in preparation, and we will see a rapid development of renewable energy. This report reviews the current situation and the future potential of renewable electrical power in Japan.