The 2–4 year part: who makes large power transformers

Every AI campus above roughly 100 MW needs a dedicated substation, and at its heart sits a large power transformer — 345 to 765 kV class, wound to order, tested to order, shipped on a truck that needs police escorts. The taxonomy behind this site carries one number on that part, and it is the number that matters: lead times of 2–4 years, flagged as the single biggest schedule risk for GW-class campuses. That is longer than it takes to build the building the transformer feeds.

Three things stand out in that table.

The listed core is European, Korean and Japanese. Siemens Energy, Hitachi Energy (inside Hitachi), GE Vernova, Hyundai Electric, Hyosung Heavy, LS Electric, Mitsubishi Electric, WEG. The US names — Virginia Transformer, Delta Star, Pennsylvania Transformer — are mostly private, which is why the public-market conversation about US transformer capacity keeps routing through the same few foreign tickers.

Several rows carry caveats. Our verify queue is honest about what’s uncertain: Prolec GE is a Xignux/GE Vernova joint venture, Efacec sits inside Mutares, Toshiba’s transformer business is private since the 2023 JIP take-private. Rows in the table tagged inferred are taxonomy placements we have not yet tied to a disclosure — the sources & method page explains the tags.

The bottleneck behind the bottleneck is steel. Transformer cores are wound from grain-oriented electrical steel (GOES), and the taxonomy’s note on that part is blunt: GOES supply is the input constraint behind transformer lead times. Cleveland-Cliffs is described there as the sole US producer — a single point of concentration two steps upstream of every data center interconnection.

None of this is a buy list. It is a map of who sits on a part whose queue is measured in years — and when queues are that long, the interesting disclosures are order backlogs and capacity additions, not quarterly shipments.