The energy storage industry just crossed another important milestone. CATL has launched the world’s first 9MWh energy storage system built for mass production. The system is called the TENER Stack.
This isn’t simply a larger container. Rather than building a single oversized unit that would trigger regulatory and logistical issues, CATL introduced a modular “two-in-one” design. Each unit remains under 36 tonnes and functions as two 4.5MWh containers stacked together. This approach meets transport regulations in 99 percent of global markets and simplifies deployment.
“9 MWh is not the limit of the energy capacity or space. Every breakthrough in energy density in the future will unleash greater energy value from a smaller footprint.” Hank Zhao, CTO of ESS Europe CATL.
According to the Chinese company, this new product enhances land-use efficiency by 40% and reduces total station construction costs by 20%.
However, this stacking approach raises critical safety and regulatory questions: What happens when vertical venting is blocked? Will European regulators accept this type of product?
The launch comes as part of a broader trend. Across the industry, storage systems are getting larger. Fluence’s SmartStack offers 7.5MWh, while Envision has introduced an 8MWh grid-scale solution. CATL’s move to 9MWh signals the next step in this evolution.
Durability Takes Center Stage
Capacity is important, but longevity may prove even more valuable. CATL has engineered the TENER Stack to deliver five years of zero degradation. This capability was first introduced in 2024 with the 6.25MWh TENER system and is now scaled up for the 9MWh version.
The technology relies on biomimetic SEI layers and self-assembled electrolytes to reduce resistance and stabilize lithium-ion movement. The result is a system that maintains its power and capacity over time, without added auxiliary power draw. It is designed to operate consistently over years of use, without the gradual losses typical of lithium-ion storage.
CATL’s Zhao says the company could extend this zero-degradation period beyond five years, but the cost trade-offs aren’t attractive to the market at this stage.
The Shift to Larger Cells
The push toward bigger systems is backed by a parallel move toward larger battery cells. The market is moving past the 280Ah and 314Ah formats and heading toward 500Ah and beyond. CATL will use 587Ah LFP cells in the TENER Stack, a major step forward in both energy density and system efficiency.
They aren’t alone. Gotion and Hithium are also working with cells in this range. Meanwhile, EVE Energy, now ranked second in global ESS battery production for 2024, has already started manufacturing 628Ah LFP cells. Their 60GWh gigafactory in China is focused on high-capacity ESS formats, with the 628Ah cell positioned as a core product.
Built to Last
CATL continues to back LFP chemistry for utility-scale storage. The choice is deliberate. LFP offers strong thermal stability, safety (vs NMC), and cost-effectiveness, especially over long duty cycles. CATL’s LFP cells are rated for up to 15,000 cycles. Combined with system design targeted at 20-year service life, the economics are hard to ignore. These systems are built to endure.
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