Baltimore Gas and Electric created Constellation as a holding company in 1999. The current iteration of the company was founded in 2022 when it split off from Exelon to become an independent firm again.
Constellation operates facilities including Calvert Cliffs Nuclear Power Plant in Lusby, Maryland, Braidwood and Byron stations in Illinois, Ginna Nuclear Generating Station in New York, Limerick Nuclear Power Plant in Pennsylvania, and South Texas Nuclear Generating Station. These sites collectively provide over 19,000 megawatts of capacity across multiple states.
Stock prices dropped 56% in a single day causing the New York Stock Exchange to halt trading after reports surfaced about exposure to Lehman Brothers following that firm's bankruptcy filing. Shares fell as low as $13 per share before the market reopened.
By 2023 Constellation held around 360 megawatts of solar assets across states including California and Texas. The company also completed construction on a 10-megawatt solar array outside Ocean City, Maryland in August 2018.
September 2024 marked when Microsoft entered a contract with Constellation to restart the undamaged nuclear reactor at Three Mile Island plant. This agreement represents one of the largest corporate power purchase agreements ever signed.