Spearmint Energy, a next-generation energy company bringing stable, secure and cost-effective energy solutions to the power grid with large-scale battery storage, today announced that Tierra Seca and Seven Flags, two 100 MW / 200 MWh Battery Energy Storage Systems (“BESS”) located in Del Rio and Laredo, respectively, within the ERCOT power market, began operation in late December 2025 and have completed nearly six months of successful operation.
Mortenson, a leading Engineering, Procurement, and Construction (“EPC”) contractor with deep experience in battery energy storage, led the construction of the projects. Tierra Seca and Seven Flags both utilise Sungrow Power Supply Co., Ltd.’s state-of-the-art PowerTitan 2.0 energy storage platform.
Andrew Waranch, Founder, President, and Chief Executive Officer of Spearmint, commented, “We are pleased to achieve commercial operation for Tierra Seca and Seven Flags. This milestone is an important step toward expanding access to reliable, safe, and cost-effective energy in ERCOT as power demand continues to rapidly grow. We appreciate the collaboration with our construction partner, Mortenson, whose team worked closely with us throughout development and construction to help bring energy storage capacity online across the region.”
Kevin Boyce, Mortenson’s Vice President and General Manager for Energy Storage, said, “Mortenson is proud to partner with Spearmint Energy as Tierra Seca and Seven Flags reach commercial operation. These projects add flexible capacity that supports ERCOT reliability and demonstrate how strong collaboration can bring complex energy infrastructure online safely and on schedule.”
This milestone follows over $250 million of construction financing Spearmint secured in Q2 2025 from Manulife, East West Bank, Investec, and Sugar Creek Capital, and the subsequent close of an investment from Kyuden International Corporation in January 2026 that supported the addition of 400 MWh of energy storage capacity to ERCOT.
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