ROUNDUP: Texas BESS updates from SolarMax, Energy Vault, Engie, and Spearmint

SolarMax’s EPC contract is expected to generate approximately US$258.1 million in revenue. The agreement will see SolarMax providing design, engineering, procurement, installation, construction, testing, startup, and commissioning services for the 600MWh BESS and the interconnection infrastructure.

The BESS project aims to enhance grid stability and promote energy affordability in Texas by storing renewable electricity for peak demand times. Once finished, SolarMax says the installation will support the region’s overall clean energy goals and help ensure grid reliability.

Earlier this week, ESN reported that SolarMax also entered into two EPC agreements for BESS projects in Puerto Rico.

The company stated that these contracts are expected to generate a total revenue of approximately US$158.3 million. SolarMax is also purchasing a 9% equity interest in each of the Puerto Rico projects.

Energy-Storage.news contacted SMA Solar, SolarMax, Navitas Energy, and AEP Texas for more information about Navboot Holdco and the Navboot BESS, but did not receive a response from any of the parties prior to publication. In the case of Navitas, the mailbox appeared to be unavailable, and the listed phone number did not connect to a working line.

Energy Vault begins construction of 300MWh SOSA BESS

US grid-scale energy storage solutions provider Energy Vault has started construction on the 150MW/300MWh SOSA BESS in Madison County, Texas.

The project, initially created by Savion, a subsidiary of oil giant Shell, was officially acquired by Energy Vault in Q4 2025 through its Asset Vault platform, with commercial operation expected by Q2 2027.

ESN reported on the acquisition in October. At the time, the company stated that SOSA’s acquisition was supported by an investment from North American infrastructure investment firm OIC L.P. and the monetisation of investment tax credit (ITC) related funds.

According to Energy Vault, the SOSA Energy Centre is the first project to begin construction under the Asset Vault investment platform.

In October, Energy Vault closed on a US$300 million preferred equity investment with OIC L.P., to launch Asset Vault.

Asset Vault is the company’s fully consolidated subsidiary dedicated to “developing, building, owning and operating energy storage assets globally.”

The company says that SOSA is “strategically positioned” within the ERCOT North market, and will make use of Energy Vault’s B-Vault AC storage solution.

Additionally, Energy Vault reports it is in advanced talks with a counterparty for an 8-year offtake agreement. The structure is anticipated to be backed by an investment-grade counterparty and is expected to generate reliable, frontloaded revenue, improving returns and reducing project cash flow risks.

The project benefits from fully secured site control, a clean title, and completed environmental and interconnection milestones. Energy Vault will handle EPC and long-term service agreements for the project.

Energy Vault claims that the Asset Vault approach secures value throughout the entire energy storage lifecycle, from development to long-term operations. The SOSA Energy Centre is projected to generate around US$350 million in total revenue, with stable, recurring high-margin cash flows over the project’s technical lifespan.

Engie faces more backlash in Fannin County, Texas

In November, residents of Fannin County, Texas spoke out against a BESS in Savoy, Texas, from Utility and power firm Engie.

Concern about Engie’s 300MW BESS is an ongoing issue. The company commenced development of the BESS several years ago; however, in May 2025, some residents claimed to have never heard of the project.

Fire risk was a primary concern. In response, Engie held an informational meeting for the residents of Savoy.

In September, as reported by local ABC outlet KTEN, Engie filed a lawsuit against the county, stating that the town officials “moved the goalposts at every turn.”

Now, as reported by local news outlet KXII, residents are speaking out against Engie and its BESS due to concerns about grid security.

At the Fannin County Commissioner’s Court, Nancy White, a member of the Secure the Texas Grid Coalition, said the Chinese Communist Party (CCP) controls 90% of all BESS globally, adding, “That’s why locations like Fannin County are so significant because nobody knows where Savoy is, but that doesn’t stop them from being a critical impact point.”

The meeting occurred only a few days after Texas Attorney General Ken Paxton launched an investigation into the use of “CCP-aligned tech products in critical state infrastructure.”

Paxton’s release specifically mentions Contemporary Amperex Technology (CATL) as a company “aligned with the CCP that could be violating state law through its involvement with a Texas power facility.”

Documents filed for the BESS project cite the ambient temperature limits for Chinese solar PV inverter and energy storage provider Sungrow’s BESS cells. It also clarifies that the project will use 87 Sungrow inverters.

The comments from the County Commissioners’ meeting highlight the increasing scrutiny of Chinese products.

Under the foreign entity of concern (FEOC) rules introduced in the ‘One Big, Beautiful Bill Act’, US downstream projects or upstream manufacturing cannot receive material assistance from prohibited foreign entities (PFEs) above specified thresholds if they wish to qualify for tax credits.

China is included in a list alongside Russia, Iran, and North Korea, all of which are already mostly restricted from accessing the US market.

Importantly, China plays a leading role in nearly every part of the supply chain, except for software, which it is already barred from.

Engie is also facing challenges, in this case, self-imposed, to the development of its Compass Energy Storage project in California.

As reported by ESN Premium earlier this week, the company asked the California Energy Commission (CEC) to pause the review of Compass, which was set for Orange County, in order to assess alternative development sites.

Engie’s request arrives just weeks prior to the CEC’s final decision, after eight months of project assessment within its opt-in certification programme. 

Spearmint Energy closes investment for 400MWh combined BESS

Battery storage developer and long-term management firm Spearmint Energy has closed an equity investment in the Tierra Seca and Seven Flags BESS projects, located in Del Rio and Laredo, Texas, respectively.

Both systems have a capacity of 100MW/200MWh. The investment was provided by Kyuden International, the overseas business arm of Japanese utility company Kyuden Group.

Kyuden International’s investment in Tierra Seca and Seven Flags represents the company’s first foray into US-based BESS, building on previous investments in a solar power portfolio and four gas turbine combined cycle power plants.

Kyuden’s investment finalises a funding package that includes over US$250 million secured in Q2 2025 from financial corporations Manulife, East West Bank, Investec, and Sugar Creek Capital. This capital supports the construction of both Tierra Seca and Seven Flags.

In 2022, ESN reported that Black Mountain Energy Storage (BMES) had signed an exclusivity agreement with Cypress Creek Renewables for the Tierra Seca and Seven Flags BESS projects, as well as two additional BESS.

EPC contractor M.A. Mortenson is spearheading the construction of both projects, which use Sungrow’s PowerTitan 2.0 energy storage platform. Both projects started operating in late December 2025.

Spearmint states that it currently manages 23 projects with a combined capacity exceeding 15GWh.

The Energy Storage Summit USA will be held from 24-25 March 2026, in Dallas, TX. It features keynote speeches and panel discussions on topics like FEOC challenges, power demand forecasting, and managing the BESS supply chain. For complete information, visit the Energy Storage Summit USA website.