Skeleton Technologies has secured a strategic investment led by Siemens that values the Estonian ultracapacitor and battery maker at more than $1 billion.
Neither company disclosed the size of the investment beyond noting a “9-figure deal”, which Bloomberg reported at more than $100 million. Siemens is taking a minority stake and gains exclusive global rights to sell and scale Skeleton’s high-power storage products for data center customers.
Separately, Estonian electrical equipment maker Harju Elekter agreed to sell part of its Skeleton stake to Siemens for €5.7 million ($6.4 million).
Skeleton said the investment will primarily go toward expanding its US manufacturing footprint and research and development in Silicon Valley, to meet demand from hyperscalers for AI data center power systems. It plans to invest more than $200 million in operational scale-up and R&D in Silicon Valley, and its US expansion includes plans for domestic cell manufacturing. It has not disclosed a site, capacity or start date for US production.
“AI is scaling faster than the power infrastructure behind it,” said Taavi Madiberk, CEO of Skeleton. “This 9-digit investment round led by Siemens gives us the industrial scale to expand manufacturing in the United States and become the only player in our segment with a full US value chain, from cells to complete systems.”
GPU smoothing
Skeleton’s products are built on its Curved Graphene ultracapacitors and SuperBattery hybrid cells, which are designed for very short, high-power events rather than multi-hour energy shifting. Its GrapheneGPU system supplies power to GPUs during compute bursts and recharges when they are idle, smoothing the load seen by the facility and the grid. The company says the system responds in 10 microseconds. Its SuperBattery cells are rated for up to 50,000 cycles and can charge in under 90 seconds.
Skeleton claims its systems can deliver energy savings of up to 40% and double-digit improvements in GPU performance. It has not named any hyperscaler customers.
“Skeleton’s portfolio perfectly complements Siemens’ comprehensive data center offering,” said Markus Grabmeier, president of electrical products at Siemens AG. “Our combined innovation roadmap will deliver benchmark solutions for the white space of next-generation data centers, delivered by a strong manufacturing network across Europe and the USA.”
Funding path
Founded in 2009 and headquartered in Tallinn, Skeleton opened a €220 million factory in Markranstädt, near Leipzig, Germany, with capacity for up to 12 million ultracapacitor cells a year, and a SuperBattery plant in Varkaus, Finland, in November 2025.
Siemens Financial Services took part in its €108 million funding round in 2023, and Siemens Digital Industries designed and automated the Leipzig factory. In May, Skeleton announced a €33 million first close of a pre-IPO round, bringing its total venture funding to €392 million, and said it is targeting a US listing in 2027.
When Skeleton launched GrapheneGPU in June 2025, it said first units would ship from Germany that month and that a second manufacturing line was planned in the US for early 2026.
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