Spearmint Energy closed an equity investment from Kyuden International Corporation to support Tierra Seca and Seven Flags, two 100 MW / 200 MWh battery energy storage systems (BESS) located in Del Rio and Laredo, Texas. The two projects add a combined 400 MWh of storage capacity to ERCOT, the Texas power grid.
Spearmint said the investment strengthens its effort to bring large-scale storage online as U.S. power demand rises and grid operators seek more flexibility and stability. For Kyuden International—the overseas business arm of Japan’s Kyuden Group—the deal marks its first U.S. battery energy storage investment, following prior investments in a solar portfolio and gas turbine combined-cycle plants.
The investment follows Spearmint’s more than $250 million financing package secured in Q2 2025 from Manulife, East West Bank, Investec, and Sugar Creek Capital to fund construction of Tierra Seca and Seven Flags. M.A. Mortenson is leading construction, and both projects use Sungrow’s PowerTitan 2.0 storage platform. Spearmint said both facilities began operating in late December 2025. Financial terms of Kyuden International’s equity investment were not disclosed.
KEY QUOTES:
“As power demand continues to rapidly increase across the U.S. accelerating the need for battery energy storage, we are pleased to partner with Kyuden International to advance our development of reliable and affordable energy solutions.”“We believe Kyuden International’s significant investment in Tierra Seca and Seven Flags underscores their confidence in Spearmint’s ability to safely and efficiently bring projects online that enhance grid stability and meet the needs of communities across ERCOT.”Andrew Waranch, Founder, President, and Chief Executive Officer, Spearmint Energy
“Our entry into the U.S. battery energy storage market required a partner with both vision and capability, and we believe Spearmint embodies both.”“Spearmint’s technical expertise, scalable platform, and execution competence in complex markets make the Company an exceptional fit for our investment strategy.”
Takashi Mitsuyoshi, CEO, Kyuden International Corporation
