Durham, NC (June 3, 2025) – FlexGen Power Systems LLC (“FlexGen”), a leading battery energy storage solution and energy management software provider, and Rosendin, the nation’s largest employee-owned electrical contracting company, are integrating their proprietary technology and solutions to leverage utility-scale Battery Energy Storage Systems (BESS) to support modern data centers without the need for traditional uninterruptible power supply (UPS) infrastructure.
The project will integrate proprietary technology and innovations from both Rosendin and FlexGen, including Rosendin’s BESSUPS design and method patent, and FlexGen’s Soft Grid Interconnection and Island Grid Transient Frequency Stabilization patents. The project will further leverage FlexGen’s Innovation Lab to integrate its powerful HybridOS energy management system. This is complimented by Rosendin’s industry leading data center delivery experience and extensive mission critical and storage energy thought leadership.
The BESSUPS system offers several advantages, namely CEBMA-quality power on an uninterrupted basis on a massive scale while avoiding the use of generators for clients choosing to decarbonize. This approach offers further benefit to the end user of dispatchable power to the Utility upon demand. This approach also allows the end user to meet the evolving power dispatch and consumption dynamic with proven Utility-scale and -grade systems.
The energy demands of AI training workloads, high-density computing, and fast-shifting loads are stretching the limits of conventional power infrastructure inside data center buildings. FlexGen and Rosendin have been working on a utility-scale battery solution outside the data center building that would be a part of the medium-voltage (1000V to 35000V) infrastructure. The companies will bring to market a first-of-its-kind BESS system that can act as a reliable, high-performance alternative to conventional UPS systems outside the data center building while simplifying system architecture and reducing capital expenditures.
Through this initiative, FlexGen and Rosendin are performing real-world, grid-connected tests that will prove:
- Existing grid-forming PCS technology can meet fast-response and waveform control requirements
- Modifications to current AC Power Conversion System (PCS) firmware enhancements from OEMs will support seamless UPS replacement functionality
- Utility-scale BESS can support mission-critical loads, enhance resiliency, and simplify transition between grid-connected and islanded modes
“As data centers scale to meet exponential demand from AI and hyperscale computing, we need to rethink how we deliver power resilience across the modern data center campus,” said Pasi Taimela, Chief Innovation Officer of FlexGen. “This effort with Rosendin enables us to bring to market a smarter, leaner, and more responsive approach to data center energy design that doesn’t require any redesigns inside the walls of the data center—one where battery systems provide both power quality and grid services without compromise.”
“Data center developers are looking for scalable and flexible power solutions that don’t compromise on performance,” said Bill Mazzetti, SVP of Rosendin. “With FlexGen’s Innovation Lab and our experience in building complex electrical systems, we’re positioned to validate a solution that helps our clients build faster, smarter, and with more confidence.”
Battery Energy Storage Systems configured as interactive UPS alternatives offer significant value across the development lifecycle—from reducing electrical footprint and construction complexity to increasing energy efficiency and operational resiliency. This solution development reflects FlexGen’s and Rosendin’s shared focus on solving the most pressing energy infrastructure challenges facing data center facilities- speed, energy costs, reliable cutovers, and power quality. Results from the integration will help inform system architecture standards, procurement planning, and large-scale deployment strategies for future data center projects and suppliers across the industry.
About Rosendin
Rosendin, headquartered in San Jose, CA, is employee-owned and one of the largest electrical contractors in the United States, employing over 7,500 people, with average annual revenues of $2.9 billion. Established in 1919, Rosendin remains proud of our more than 100 years of building quality electrical and communications installations and value for our clients but, most importantly, for building people within our company and our communities. Our customers lead some of the most complex construction projects in history and rely on us for our knowledge, ability to scale, and dedication to quality. At Rosendin, we work to ensure that everyone can reach their full potential by building a diverse, safe, welcoming, and inclusive culture. For more information, visit www.rosendin.com.
Rosendin Energy Group (REG) is an EPC providing renewable, microgrid and mixed modality energy plant design, planning, and construction for a wide variety of energy projects. s. REG has installed nearly 9 GW of Utility-scale power throughout the U.S. and offers a comprehensive portfolio of construction services including design-build, substation and switchyard installation, plant construction, vertical tower wiring, overhead collection systems and transmission lines, AC & DC collection systems, and substation design and communications integration.
About FlexGen Power Systems, LLC.
FlexGen provides industry-leading software and services for deploying, managing and optimizing battery energy storage systems. FlexGen leverages decades of engineering, procurement and software expertise to solve today’s toughest energy challenges that enable the transition to a modern electric grid. FlexGen HybridOS energy management software seamlessly integrates with any battery OEM and offers advanced analytics and AI-driven insights that allow energy storage owners to deploy diverse power market strategies and integrate various generation forms, enhancing grid stability and economic returns. With 1.5M hours of runtime and more than 10 GWh of energy storage systems enabled by FlexGen, we are trusted by the most technically and commercially demanding developers, utilities, government agencies, and industrial companies in the world.
For media inquiries, please contact:
krelja@flexgen.com and sbown@rosendin.com
Forward-looking statements: This press release contains forward-looking statements regarding future operations, project timelines, and market growth. Actual results may vary based on external factors and market conditions.
