Iron-sodium battery makers Inlyte Energy just crossed an important line from lab to grid reality. The company has completed a factory acceptance test of its first field-ready iron-sodium battery energy storage system with reps from a major US utility in attendance.
Iron-sodium battery storage
The test took place at Inlyte’s facility near Derby in the UK, and was witnessed by representatives from Southern Company, one of the largest electric utilities in the US. The goal was to prove the performance and integration readiness of the whole system, which combines sodium metal chloride battery cells with inverters and control electronics. By Inlyte’s account, the system performed as expected and is ready for field deployment.
The energy storage market is growing fast, and utilities are looking beyond lithium‑ion. Iron-sodium battery storage systems are emerging as a compelling alternative to lithium-ion batteries for grid-scale use, as they rely on abundant, low-cost materials and offer strong safety and long-duration performance.
While lithium-ion batteries excel at fast response and short-to-medium-duration storage, iron-sodium systems are better suited for multi-hour to multi-day grid applications where cost, thermal stability, and long service life matter more than energy density.
The global energy storage market is projected to grow from approximately $70 billion in 2025 to over $150 billion by 2030. The US Department of Energy estimates the grid will need more than 225 gigawatts of long‑duration energy storage by 2050.
Inlyte is betting that iron‑sodium batteries can help fill that gap. The system tested in the UK utilizes what the company claims are the world’s largest sodium metal chloride battery cells and modules ever built, each capable of storing more than 300 kilowatt-hours of energy. The chemistry is designed to be lower-cost, safer, and longer-lasting than lithium-ion – key traits for grid-scale storage.
During the factory test, Inlyte’s battery system hit 83% round‑trip efficiency, including auxiliary loads. That puts it in the same range as high-performance lithium-ion systems and well above the roughly 40% to 70% efficiency typical of many other long-duration energy storage technologies. Southern Company’s R&D team observed the test in person, a step that helps clear the way for real‑world deployment.
The commercial plan
Next up: the field. Inlyte says its first energy storage systems will be installed at Southern Company’s Energy Storage Test Site in Wilsonville, Alabama, in early 2026. Those deployments will allow the utility to study how the iron‑sodium batteries perform under real grid conditions.
With technical readiness now demonstrated, Inlyte is turning its focus to US manufacturing. The company plans to finalize a site for its first domestic factory in 2026. To help speed that process, Inlyte has partnered with HORIEN Salt Battery Solutions, the world’s largest producer of sodium metal chloride batteries. HORIEN brings over 25 years of commercial experience across applications like critical power, remote industrial sites, and battery energy storage.
The plan is to combine HORIEN’s manufacturing know‑how with Inlyte’s system integration work to bring sodium‑based grid batteries to the US market. If all goes according to plan, Inlyte expects commercial deliveries of domestically produced systems to begin in 2027.
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