US-based renewable energy company Spearmint Energy has achieved commercial operation for two standalone battery energy storage system (BESS) projects in Texas, adding a combined 200 MW / 400 MWh of capacity to the ERCOT power market.
Both projects, the Tierra Seca and Seven Flags, each have 100 MW / 200 MWh batteries, located in Del Rio and Laredo, respectively. Spearmint Energy confirmed that they began operations in late December 2025, approaching the six-month anniversary of successful operations.
Mortenson led the engineering, procurement, and construction (EPC) for the projects, and both sites utilize Sungrow’s PowerTitan 2.0 energy storage platform.
Spearmint founder, president, and chief executive officer Andrew Waranch said the milestone was achievable thanks to the support from Mortenson.
“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,” Waranch said.
Mortenson’s vice president and general manager for energy storage, Kevin Boyce, 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.”
Spearmint Energy currently operates 350 MW / 700 MWh in ERCOT, with more than 20 projects, over 15 GWh of capacity, under development in 13 states across five US regions. Spearmint Energy had previously secured equity investment for the Tierra Seca and Seven Flags projects from Kyuden International Corporation. It also obtained more than $250 million of construction financing Spearmint secured in Q2 2025 from Manulife, East West Bank, Investec, and Sugar Creek Capital.
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