How much of Japan's electricity can be generated by renewable energy (RE)? America's Berkeley National Laboratory and Japan's Ministry of Economy, Trade, and Industry (METI) have very different assessments. I think Berkley's is more realistic.
           According to Berkeley Lab, by 2035, it is both technologically and economically feasible for Japan to get 70% of its electricity to come from RE, mostly solar and wind. Moreover, doing so would lower wholesale electricity costs by 6% from the 2020 level.
           Berkeley's vision is a mirage, contends the Ministry of Economy, Trade, and Industry (METI ), which contends that geography and the laws of physics create insurmountable barriers. Solar and wind need an enormous amount of suitable land, but Japan lacks enough of such land. 66% of the country is covered by forests. Moreover, due to the earth's tilt and Japan's mountainous topography, a square meter of land in Japan gets less energy from sunlight than in many other countries.

For details, see https://richardkatz.substack.com/p/70-renewable-energy-by-2035-physics

Richard Katz