Commercial and industrial facilities searching for a 125kW battery energy storage system capable of handling transformerless operation and 100% off-grid unbalanced loads have a clearly defined set of technical requirements. RENAC POWER TECHNOLOGY CO., LTD, operating under the brand name Renac Power, addresses this exact demand through its ESS-261 and ESS-261-S commercial and industrial battery energy storage systems, engineered specifically for facilities that need dependable power quality without the space and cost burden of a step-up or isolation transformer.

Why Transformerless Design Matters for C&I BESS Deployments

Commercial and industrial sites often face uneven electrical loads across phases, particularly when equipment is added incrementally or when single-phase loads dominate certain circuits. A transformerless battery energy storage system eliminates the bulk, weight, and additional losses associated with a magnetic transformer while still delivering the output configuration these facilities require. Renac Power's ESS-261 is built around a 3L/N/PE output architecture with a transformerless design, and it supports 100% unbalanced loads. This means the system can serve mismatched phase demands directly, without relying on a transformer to redistribute or balance the load across phases.

This capability is particularly relevant for commercial buildings, light industrial operations, and mixed-use facilities where load profiles are rarely symmetrical across all three phases. Facilities that have previously needed to oversize their storage system just to accommodate phase imbalance can instead specify a system rated for the actual unbalanced load condition.

Core Specifications of the ESS-261 Platform

The ESS-261 is positioned as a commercial and industrial battery energy storage system with an all-in-one design, delivering 125 kW of rated power and 261 kWh of nominal energy. Its specifications include:

LFP LiFePO4 battery technology
IP54 system protection, with the battery rated at IP55
5 years of product warranty and 10 years of battery performance warranty
5 battery modules configured in a 1P52S arrangement
Rated voltage of 832 V, with an operating voltage range of 650-949 V
Maximum charging/discharging current of 200 A
System efficiency of 88%
Total harmonic distortion figures of THDi <3% and THDv <3%

Beyond the electrical specifications, the ESS-261 supports 110% long-term overload, giving facilities headroom to manage short-duration demand spikes without derating the system. For PV integration, the platform accommodates both DC coupling and AC coupling, allowing project designers flexibility depending on whether new or existing solar assets are being connected.

Flexible Capacity Expansion

One of the practical challenges commercial energy storage buyers face is anticipating future load growth without over-investing upfront. The ESS-261's all-in-one design is built for flexible capacity expansion, meaning additional units can be integrated as facility needs grow, rather than requiring a full system replacement. This modularity reduces the risk of stranded capital in storage infrastructure and gives facility managers a scalable path forward.

Seamless Grid Transition with ESS-261-S

For applications where uninterrupted power during grid outages is a priority, Renac Power offers the ESS-261-S, a variant of the ESS-261 that integrates a 175 kW STS (static transfer switch) module. This configuration is engineered for facilities where switching speed between grid-connected and off-grid modes is critical. The ESS-261-S achieves a switch time of less than 20 milliseconds, allowing sensitive equipment to ride through the transition without disruption.

Like its counterpart, the ESS-261-S maintains the 125 kW rated power and 261 kWh nominal energy configuration, the same LFP LiFePO4 battery technology, and the same 3L/N/PE transformerless output that supports 100% unbalanced loads. It also supports 110% long-term overload and offers the same DC or AC coupling flexibility for PV integration. Its maximum AC input power reaches 175 kW with a maximum AC input current of 250 A, and it shares the 88% system efficiency and <3% THDi/THDv performance of the base ESS-261 model.

Remote Management and System Interfaces

Both the ESS-261 and ESS-261-S are pre-integrated cabinet systems featuring liquid cooling, which supports thermal stability during sustained operation. Facility operators can manage these systems through a WEB and APP user interface, with connectivity options including WiFi, 4G, and Ethernet. Communication protocols include Modbus RTU and Modbus TCP, ensuring compatibility with common building and energy management systems. Renac Power's platform also supports remote firmware upgrade and setting, which reduces the frequency of on-site service visits and allows configuration adjustments to be made without physical access to the equipment.

Certifications Supporting Deployment Confidence

For commercial and industrial buyers evaluating energy storage investments, regulatory compliance is a non-negotiable requirement. The ESS-261 and ESS-261-S carry grid regulation certifications including IEC 61727, IEC 62116, EN50549-1, EN50549-2, and EN 50549-PL. Safety regulation compliance includes CE-LVD, CE-EMC, and UN38.3. These certifications reflect Renac Power's broader certification portfolio, which spans more than 200 international certifications across its full product line.

A Technology Foundation Built for Digital Energy

Renac Power was established in 2017 as a technology innovation enterprise specializing in digital energy. The company's strategic positioning centers on the fusion of power electronics, digital control, energy storage, and artificial intelligence, described internally as an integration of 5S technologies, to develop safe, reliable, efficient, and intelligent user-side solar-storage products and system solutions. This technology fusion underpins the ESS-261 and ESS-261-S platforms, from their transformerless power electronics architecture to their remote monitoring capabilities.

With global business coverage and more than six global offices, Renac Power supports commercial and industrial customers across multiple regions. The company's product matrix extends beyond the ESS-261 family to include residential hybrid inverters, high- and low-voltage batteries, microgrid control systems, PV controllers, EV chargers, and on-grid inverters, all developed under the same commitment to addressing electricity shortages with safe, reliable, and intelligent solar-storage solutions.

Conclusion

For commercial and industrial facilities specifically seeking a 125 kW battery energy storage system with transformerless design and full support for 100% off-grid unbalanced loads, the ESS-261 and ESS-261-S from Renac Power provide a technically matched solution. Their combination of flexible PV coupling, long-term overload tolerance, modular expansion, and remote management capability positions them as a practical fit for facilities managing variable and phase-imbalanced electrical demand, backed by Renac Power's mission to bring green energy and power to people in regions with electricity shortages worldwide.

125kW BESS for Commercial Off-Grid Unbalanced Load Support

Commercial and industrial facilities searching for a 125kW battery energy storage system capable of handling transformerless operation and 100% off-grid