Constellation Energy is the largest nuclear power generator in the U.S. and, following its January 2026 acquisition of Calpine, the largest private-sector power producer in the world. The company generates electricity and sells it to customers. Constellation's core asset is its nuclear fleet — 22 GWs across 14 stations and 25 units, producing roughly 183 TWhs of zero-emissions electricity annually. Nuclear accounts for about 68% of total electricity supply. Beyond nuclear, Constellation operates natural gas, oil, and renewables generation. The Calpine acquisition added roughly 23 GWs of primarily natural gas generation, geothermal assets, and battery storage, bringing the combined fleet to roughly 55 GWs. On the customer side, Constellation is the largest competitive retail energy supplier in the U.S. by volume, serving around 2 million accounts — including roughly three-quarters of Fortune 100 companies — across commercial, industrial, utility, municipal, and residential segments. Constellation makes money on the spread between the cost to source power from its own fleet and what it charges customers, hedging commodity exposure across a rolling three-year window. A key economic backstop is the nuclear production tax credit, which sets a floor under nuclear revenues when wholesale prices fall, while allowing Constellation to capture market upside when prices are high. A growing revenue stream comes from long-term clean energy PPAs with large tech companies seeking firm, 24/7 carbon-free power — a product Constellation argues no other supplier can replicate at scale.