Siemens Turns Skeleton Technologies Into a Unicorn

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Anyone building A.I. data centers needs shock absorbers for the power supply, and Siemens has just locked in one of the key makers: The Munich-based technology group is leading a new funding round in Skeleton Technologies. The Estonian energy storage company is now valued at more than $1 billion (about €855 million), making it officially a unicorn. Skeleton did not disclose the amount. In a news release, its chief executive, Taavi Madiberk, described it as a “9-digit investment round,” meaning at least $100 million (about €85 million).

It is Skeleton’s second big step in just a few months. In May, the company announced the first close of a €33 million round and said it was preparing for a U.S. initial public offering in 2027 (as Trending Topics reported). Axon Partners Group, SmartCap and Taiwania Capital joined as investors at the time, bringing Skeleton’s total venture funding to €392 million.

Siemens Gets Exclusive Sales Rights

The centerpiece of the deal is an exclusive partnership: Siemens gets worldwide exclusive rights to sell and scale Skeleton’s products in the data center market, the group said in a press release. Skeleton’s supercapacitors will become part of Siemens’s electrical infrastructure portfolio, which now stretches from the grid connection to the A.I. rack. According to Siemens, nine of the world’s 10 largest data center operators already rely on the company.

The relationship is not new. Siemens has worked with Skeleton as a technology partner since 2022 and has been an investor since 2023. Siemens Digital Industries also designed and automated Skeleton’s SuperFactory in Markranstädt, near Leipzig, Germany. The transactions are still subject to customary closing conditions.

“The race to scale A.I. is increasingly becoming a race for energy,” said Peter Koerte, a member of the Siemens managing board and head of its Smart Infrastructure business. Operators need ways to expand capacity without waiting years for new grid and facility infrastructure, he added.

Why GPUs Need Shock Absorbers

The problem Skeleton wants to solve plays out in milliseconds. Thousands of GPUs in an A.I. cluster work in lockstep, switching between idle and full load at the same time. According to Siemens, these swings add up within seconds to load jumps in the megawatt range that strain both equipment and the grid. Skeleton’s supercapacitors, based on its proprietary Curved Graphene material, absorb these spikes close to the hardware. The company promises up to 40 percent energy savings and double-digit gains in GPU performance.

Mr. Madiberk is not short on confidence. “In A.I. infrastructure, supercapacitors are becoming the new semiconductors,” he said. What matters, in his view, is how much compute can be extracted from every GPU and every available megawatt. His stated goal is to make Skeleton the world’s largest supplier of power systems for the server floor of A.I. data centers.

The market is growing fast. Skeleton cites International Energy Agency figures projecting that global data center electricity consumption will nearly double, from about 485 terawatt-hours last year to 950 terawatt-hours in 2030. In the United States, data centers are expected to account for about half of the growth in electricity demand, which is already driving plans for new gas power plants.

More Than $200 Million for the United States

Most of the new money will go to the United States, home of the big hyperscalers. Skeleton plans to invest more than $200 million (about €171 million) in scaling up production and in research and development in Silicon Valley. It also plans its own U.S. cell manufacturing, giving it a full American value chain from cells to complete systems. Where and when U.S. cell production will start has not been disclosed.

Founded in 2009 by Mr. Madiberk and Oliver Ahlberg, the company currently makes supercapacitors in the German state of Saxony and runs a SuperBattery factory in Finland. Skeleton did not say whether its new valuation brings the planned 2027 U.S. listing any closer.

The Competition

Skeleton is far from the only company using supercapacitors to tame A.I. power spikes:

• Eaton: The U.S. power management company sells the XLHV, a supercapacitor bank the size of a single rack unit that can deliver up to 420 kilowatts and is already deployed in data centers.
• Siemens Energy: The energy technology group, spun off from Siemens in 2020, offers E-statcom, a supercapacitor system for entire data centers that can buffer up to 75 megawatts per unit.
• Delta Electronics: The Taiwanese power supply maker relies on its own capacitor shelf for server racks.
• Nvidia: Working with LITEON, the chip giant has already built energy storage for smoothing power spikes directly into the racks of its GB300 NVL72 systems.

With Siemens as its exclusive sales partner, however, Skeleton now has a direct line to the very hyperscalers buying these solutions at scale.