Estonian supercapacitor maker Skeleton Technologies topped a $1 billion valuation after Siemens AG closed a strategic investment and exclusive partnership.

The deal targets what both companies call the central constraint on data center expansion: massive, rapid, and recurring swings in electricity demand from AI compute racks.

Why supercapacitors?

Skeleton builds high-power energy-storage systems that absorb sharp load fluctuations in under one millisecond. The company claims its systems smooth power demand and cut energy consumption at AI data centers without choking compute density.

Peter Koerte, member of the Siemens managing board and president of smart infrastructure, framed the logic. "By combining Siemens' electrical infrastructure expertise with Skeleton's breakthrough supercapacitor technology, we can help customers unlock more AI capacity, improve resilience and accelerate growth in a rapidly expanding market," Koerte said.

What does this change for AI data center operators?

Operators gain an integrated power stack — Siemens' switchgear (high-voltage circuit control hardware) and transformers paired with Skeleton's shock-absorber storage. The pitch: ride through demand spikes, protect grid-tied equipment, and keep dense AI compute racks fed through power transients that would otherwise stress downstream hardware.

Skeleton CEO Taavi Madiberk laid out the ambition. "Our partnership with Siemens brings together Skeleton's innovation and Siemens' global industrial scale to accelerate the deployment of AI infrastructure," Madiberk said. He added that the company plans to become "the world's largest provider of white-space power systems for AI data centers" — the power distribution gear sitting between the grid feed and the server racks.

A wider build-out

The Siemens tie-up slots into a broader commercial push. Skeleton has stacked data-center-focused partnerships across the supply chain this year:

• A deal with transformer maker DG Matrix to push 800VDC (800-volt direct current) power architecture, replacing the 400V AC distribution still common in legacy halls.
• A co-development pact with German chipmaker Infineon for high-efficiency, resilient power-conversion circuits.

Skeleton also launched a new UPS (uninterruptible power supply) for AI data centers. The system delivers continuous backup power while complying with grid-connection rules, the company said.

Manufacturing footprint

A Houston factory opened earlier this year — Skeleton's first US site. Two European plants followed in November 2025: a $270 million site in Germany and a $60 million plant in Finland.

The company started in 2009 in Tartu, Estonia. First customer: the European Space Agency. Skeleton's ultracapacitors (a related class of high-power storage) also ride in BMW's i7 and M-series vehicles, a German automotive proving ground the company cites often.

Terms remain thin

Siemens did not disclose the investment size or equity stake. Neither company named a timeline for joint products. A billion-dollar-plus valuation suggests Siemens paid a premium; the price tag stays private for now.