Kagawa-based quarrying and stonework company Nakayoshi Sekizai will retrofit all three of its solar power plants in Kyushu with battery storage and switch the them from the feed-in-tariff (FIT) to the feed-in-premium (FIP) scheme with TESS Engineering’s support, TESS Holdings announced on September 25, 2025.
According to the statement, TESS Engineering will install a total of 22.35MWh of Huawei BESS units across the three sites and handle the solar-plus-storage assets’ aggregation once they begin operation under FIP. The projects are expected to be completed in April 2026.
Two of the assets, including a 1MWAC/1.21MWDC power plant in Yusui Town and a 1.75MWAC/2.3MWDC project in Kirishima City, are in Kagoshima Prefecture and were built by TESS Engineering, which has also been in charge of their operation and maintenance (O&M). They were commissioned in 2018 and 2014, respectively. The third, 1.75MWAC/2.63MWDC project is located in Kusu Town, Oita Prefecture, and was commissioned in 2020.
TESS Engineering plans to add a 1.28MW/4.47MWh BESS to the smaller facility and 2.56MW/8.94MWh systems to the two 1.75MWAC plants.
Nakayoshi Sekizai currently operates the Oita asset under a contract secured in FY2012, when 10kWAC and larger solar power plants were offered a 40 yen per kWh tariff. The two Kagoshima power plants are under FY2013 contracts, when the rate was reduced to 38 yen per kWh. METI data shows the company also owns 50kWAC/83kWDC and 500kWAC/765kWDC power plants in Miki Town, Kagawa Prefecture with more recent FIT contracts.
The deal highlights the opportunity for companies with industry experience to support non-energy companies that invested in solar assets in the early years of the FIT scheme with retrofitting them with BESS and converting them to the FIP scheme amid increasing curtailment.
