Limited access to the power transmission network has been deemed one of the factors hampering the growth of renewable energy in Japan. Major power companies that own the transmission network have often refused to buy electricity from solar and wind power generators on the grounds there was no spare capacity in the transmission system. That explanation has been challenged by a university professor's research, and the government and the power industry are reviewing regulations to pave the way for renewable energy firms to use the surplus capacity. To significantly boost the power supply from renewable sources — as the draft of the government's new Basic Energy Plan advocates — both the government and the power industry need to maximize efficient use of the transmission network.
Since the introduction of the feed-in tariff system in 2012, in which electricity generated by renewable sources is bought at pre-determined advantageous prices to promote their use, solar and wind power facilities have been launched in large numbers across the country — with solar power generation expanding sevenfold since before the FIT system was launched. Still, renewable energy including large-scale hydro power accounted for just 15.3 percent of Japan's electricity supply as of 2016, compared with 26 percent in Britain and 30 percent in Germany in 2015.
The high cost of renewable energy in Japan is often cited as a major reason behind the slow growth: It costs ¥21 to generate 1 kilowatt-hour of electricity via solar power and ¥22 via wind power, compared with a global average of ¥10. Aside from the cost problem, renewable power generators have frequently been denied access to the power transmission system owned by major power companies, which monopolized the regional power supply before the electricity business was liberalized.