What NGK built, and how big it got
A sodium sulphur battery stores electricity in sodium and sulphur held as liquids instead of solids, at high heat. NGK Insulators, the Japanese company that makes nearly all the sodium sulphur batteries used worldwide, reports its batteries running at over 250 locations, with a combined output of over 720 megawatts, the rate at which a system can push power into the grid, and total storage of approximately 5,000 megawatt hours, the amount of energy those systems can hold at once, as of 2024. The single largest national total sits in Japan, at 430 megawatts, counted in a 2021 presentation by the company.
Figures are NGK own count as of a March 2021 presentation. The company reported a larger worldwide total, over 720 megawatts, by 2024, after this snapshot was taken.
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| Japan, national total | 430 |
| Abu Dhabi, 11 substations | 108 |
| Buzen Power Plant, Japan | 50 |
| Catalina Island, California | 1 |
NGK installed 108 megawatts across 11 substations in Abu Dhabi. A system at the Buzen Power Plant in Japan has run since March 2016 at 50 megawatts and 300 megawatt hours of storage. A single 1 megawatt unit holding 7.2 megawatt hours on Catalina Island in California had run 9 years with no major failure and no battery replacement, as of the same 2021 count.
The national total for Japan has no matching megawatt hour figure in the source and is left out of this chart rather than estimated.
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| Abu Dhabi, 11 substations | 648 |
| Buzen Power Plant, Japan | 300 |
| Catalina Island, California | 7.2 |
Why the technology never left the grid
A sodium sulphur battery only works while its sodium and sulphur stay molten, meaning heated past the point where they melt and kept liquid, at 300 to 360 degrees Celsius, the range NGK states for its own product. Below 280 degrees Celsius, a peer reviewed review of the chemistry states, the material inside solidifies and stops conducting electricity properly. The same review states the battery is built for stationary use, not a moving vehicle, which is why sodium sulphur batteries run substations and never cars.
The decision that ended it
The sodium sulphur battery business brought in 41.97 million dollars in sales for NGK in the year ending March 2025, about 1% of total company sales. On 31 October 2025, the NGK board resolved to stop manufacturing and selling the battery and to stop taking new orders, while continuing to service the sites already running. NGK had spent since 2019 developing a newer version, the NAS Model L24, together with BASF, but BASF withdrew financial support for that partnership in September 2025 under its newly appointed chief executive, Markus Kamieth, and a search for another backer did not succeed.
Gauthier Dupont, director of strategy and partnerships for the energy storage business NGK runs in Europe, put it this way.
It's still a great technology that maybe was not in the right environment, in the right time.
Gauthier Dupont, director of strategy and partnerships for the energy storage business NGK runs in Europe. Source 3.