Replacing destroyed EHV transformers after an EMP takes 18-36 months per unit

Extra-high-voltage (EHV) transformers — the 345 kV to 765 kV units that form the backbone of the U.S. bulk power system — are custom-built to order. There is no domestic U.S. manufacturer of EHV transformers above 345 kV; nearly all are made by Siemens (Germany), ABB (Switzerland), Hyundai (South Korea), or TBEA (China). Each unit takes 12-18 months to manufacture, weighs 200-800 tons, and requires specialized railcars (Schnabel cars, of which fewer than 30 exist in North America) for transport. If a HEMP event destroys even 9 of the roughly 2,000 EHV transformers in the U.S. — which the EMP Commission considered a conservative scenario — the replacement timeline extends to 3-5 years because manufacturers cannot surge production. During that period, entire regions lose bulk power transmission. You cannot reroute around missing EHV transformers the way you reroute internet traffic; the physics of power flow means load must be shed, resulting in rolling or permanent blackouts for millions. This persists because the transformer supply chain was optimized for efficiency, not resilience. Domestic manufacturing was offshored decades ago because foreign producers offered 20-40% cost savings. Congress authorized a Strategic Transformer Reserve in the FAST Act (2015), but as of 2025, the reserve contains fewer than 10 units — enough to replace routine failures, not a coordinated attack. The economics of maintaining surge manufacturing capacity for a once-in-a-century event are unfavorable for any single company.