From 1 April, tariffs for solar power will be lowered to JPY 24/kWh ($0.21) from JPY 27/kWh ($0.24).
Solar power tariffs are now around 40% lower compared with the JPY 40/kWh ($0.36) tariff set at the 2012 launch of the feed-in tariff system in Japan, due to overdevelopment.
The move follows a cabinet decision in early February to amend a law governing the use of waters in ports, allowing offshore developers to occupy harbour space for a period of 20 years, far exceeding existing arrangements.
The decision aims to set in place a comprehensive guideline for local governments to follow.
"So far, wind developments have been viewed as temporary or short term in nature, but this amendment helps clarify their long-term nature," said a spokesman for the Ministry of Land, Infrastructure, Transport and Tourism.