Astmax-affiliated Kumamoton Solar Project will retrofit its 7.10MWAC/8.19MWDC Kumamoton Solar Power Plant in Kikuchi City, Kumamoto Prefecture, with a 2MW/12.9MWh battery system system and convert the asset from the feed-in-tariff (FIT) to the feed-in-premium (FIP) scheme, the company announced on May 22, 2026.
According to the statement, the project will use 60 Huawei 215kWh units. Construction is scheduled to begin in July 2026 and finish in March 2027. FIP operations are scheduled to start in June 2027. Astmax will aggregate the asset in-house.
TESS Engineering will handle the battery system’s engineering, procurement, and construction (EPC), and remain in charge of its operations and maintenance (O&M) after commissioning. The Bank of Kochi, which provided project finance for the solar power plant, will also fund the retrofit.
The existing project was FIT-certified in FY2012, when 10kWAC and larger solar power plants were eligible for a 20-year, 40-yen-per-kWh tariff. It was commissioned in July 2016 and operates under a contract valid until June 2036.
Kumamoton Solar Power Plant is one of seven solar projects in Astmax’s 13.1MWDC operational portfolio. The company also leases land and provides O&M services to other asset owners.
An increasing number of owners of early FIT-certified solar power plants are retrofitting their assets with battery storage and transitioning them to FIP to reduce curtailment losses and shift power sales to higher-priced periods. The strategy has gained particular traction in Kyushu, which sees the highest solar curtailment rates among Japan’s 10 TSO areas.
