FlexGen has acquired Clean Energy Services (CES), a US-based services company that has to date commissioned more than 15GWh of battery energy storage system (BESS) projects.
Durham, North Carolina-headquartered BESS system integrator FlexGen announced the deal last Thursday (2 April). Financial terms were not disclosed.
FlexGen, a software-focused company onboarding its HybridOS energy management system (EMS) and controls and data platform to third-party systems from suppliers such as CATL and Hithium, said it will create an integrated model that combines with CES’s commissioning and lifecycle services teams.
CES, which claims to have the biggest BESS commissioning team in the US, has partnerships with other BESS OEM suppliers that FlexGen could now work with through CES authorised service provider (ASP) channels.
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The acquisition target also provides services for utility-scale solar PV, giving its new owner the opportunity to expand the horizons of the recently launched FlexGen HybridOS Solar power plant controller (PPC) offering.
As clean energy developers and their investors increasingly consider commissioning speed and asset availability once operational among the most important aspects of industry competitiveness, FlexGen claimed the CES acquisition will strengthen its position in both areas.
CES will now operate as a subsidiary of FlexGen, maintaining continuity of service for existing customers, who will now be offered the HybridOS platform.
CES will continue to operate its remote operations centre (ROC) in Houston, Texas, managing fleets of more than 1GW of solar PV and 4.5GWh of battery storage. FlexGen’s own ROC is in Durham, from where it provides 24/7 monitoring, root-cause analysis of operational issues and dispatching field services.
The two companies have partnered on BESS projects “for years,” CES CEO Ahmad Atwan said, with the new integrated structure enabling CES “to deliver more robust solutions across a complementary set of customers and markets.”
Deal follows 2025 FlexGen acquisition of Powin’s assets
FlexGen got its start in 2009 as a developer of microgrid projects in remote locations around the world, increasingly pivoting towards demanding applications for large-scale BESS that nonetheless leveraged the experience built up in delivering software-backed integration in off-grid projects that often called for the orchestration of different energy technologies and support for weak or unstable grid environments.
In summer 2025, the integrator bought “almost all the assets” of fallen rival Powin, which went bankrupt earlier in the year. Powin had deployed 11.3GWh of systems since the mid-2010s, but according to industry expert Drew Leibowitz of consultancy PowerSwitch Advisory, it had most likely struggled to compete by manufacturing BESS using third-party battery cells, when those battery OEMs, typically from China, were also integrating their cells into their own BESS solutions at lower cost.
FlexGen CEO Kelcy Pegler told ESN Premium in an exclusive interview in August 2025 that, in addition to representing economic value, the transaction enabled his company to uphold the legacy of “significant” work Powin had done as an early mover in the integration space. Powin systems would be serviced by FlexGen teams, ensuring continuity, while the new owner also got Powin’s hardware and software IP.
On the CES acquisition, a FlexGen spokesperson said it strengthens the company’s ability “to deliver high-performance systems and services with strong field execution and support power quality and reliability by minimising downtime and maximising long-term performance.”
