ESS Tech launches 1.2-MWh sodium-ion rival to Tesla Megapack
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- ESS Tech launched the ESS Bridge, a 1.2-MWh sodium-ion battery system announced July 8 for utility, commercial, industrial, and data center customers.
- The modular ESS Bridge stacks to deliver up to 4.8 MWh in a standard 20-foot container, roughly matching the latest Tesla Megapack in capacity.
- ESS Tech has attracted over $1 billion in "early-stage customer opportunities" since late April, when it announced a deal to procure 8.5 GWh of sodium-ion cells and modules from Alsym Energy.
- Peak Energy, another sodium-ion player, is building a 4-GWh manufacturing plant in Sacramento with General Motors and previously committed up to 4.75 GWh of batteries to Jupiter Power by 2030.
- ESS Tech spent 15 years commercializing iron flow batteries; its stock has collapsed from nearly $300/share after its 2021 reverse merger to under $1/share today.
- CEO Drew Buckley said sodium-ion handles AI data center workloads more effectively than conventional tech, and proponents cite lower thermal runaway risk — a point underscored by the early-2025 fire that destroyed most of a 300-MW Vistra storage facility near Santa Cruz, California.
- Sodium-ion production and installed capacity still trail lithium-ion, and sodium's more-than-3x heavier atomic weight means a larger footprint for equivalent energy capacity.
Why it matters: Data center operators and utilities gain a domestically sourced, thermally stable alternative to lithium-ion grid storage at Megapack-competitive scale, and ESS Tech's $1 billion pipeline signals real market pull. However, sodium-ion's lower energy density means it will supplement rather than replace lithium at space-constrained sites.
