Constellation Energy makes money by generating electricity and selling it to customers across the United States. The company runs the largest nuclear power fleet in the country, with ownership interests in 14 nuclear stations. It also owns natural gas plants, hydroelectric dams, wind farms, and solar facilities. On top of generating power, Constellation sells electricity and natural gas directly to about 2 million customer accounts, including three-quarters of the Fortune 100 companies. Customers pay for power they consume continuously, so revenue keeps coming in as long as the lights stay on. The diagram below traces where the money goes.

Five years of financial data tell a complicated story. Revenue grew from $19.6 billion in 2021 to $25.5 billion in 2025, which looks healthy on the surface. But for most of that period, the company was burning through cash rather than generating it. Operating cash flow was negative every year from 2021 through 2024, reaching as low as negative $5.3 billion in 2023. Free cash flow was even worse, hitting negative $7.7 billion that same year. That means the company was spending far more cash than it was bringing in from its operations.

Then 2025 arrived and things changed. Operating cash flow swung from negative $2.5 billion in 2024 to positive $4.2 billion in 2025. Free cash flow turned positive for the first time in five years, reaching $1.3 billion. Net debt also fell sharply, from $8.8 billion in 2023 to $4.4 billion in 2024, before edging back up to $5.3 billion in 2025. One year of positive cash flow after four deeply negative years is meaningful, but it is still just one year.

The shift toward long-term contracts with large technology companies is one of the most important recent developments. Data centers need power around the clock, and nuclear plants are one of the few sources that can deliver that reliably without emitting carbon. Constellation's nuclear fleet produced 183 terawatt-hours of zero-emissions electricity in 2025, enough to power 16 million homes according to the company. Its nuclear plants ran at a capacity factor of 94.7% in 2025, meaning they were generating power almost all of the time. The industry average is roughly four percentage points lower, according to the company's own filing.

Then there are the risks that could disrupt this picture. The most immediate involves geography. About 70% of Constellation's power plants sit inside the PJM grid region, which covers the mid-Atlantic and Midwest states. If PJM changes its market rules, or if federal regulators step in, the prices Constellation can charge could fall sharply. The company's filing notes that rule changes could force early plant closures or require plants to run at a loss. In January 2026, the National Energy Dominance Council was already pushing PJM to revise its pricing rules, which the filing describes as an emerging issue with potential to impact future revenues.

A second risk sits on the balance sheet in the form of nuclear decommissioning obligations. Constellation has set aside money in trust funds to cover the future cost of shutting down its nuclear plants safely, but those obligations stood at $12.9 billion as of December 31, 2025. If the trust fund investments perform poorly, or if decommissioning costs rise faster than expected, Constellation may have to contribute hundreds of millions of additional dollars from its operations. A third risk is nuclear fuel supply. U.S. sanctions now ban imports of Russian uranium. Russia also imposed restrictions on uranium exports to the U.S. in late 2024. Constellation says it has long-term contracts with a diverse set of suppliers, but the filing acknowledges that losing a key supplier could prevent it from operating its nuclear plants.

The biggest near-term financial risk may be the January 2026 acquisition of Calpine for approximately $22 billion. Calpine adds about 23 gigawatts of natural gas and geothermal generation capacity and makes Constellation the largest private-sector power producer in the world. But the deal is expected to add a significant amount of goodwill to the balance sheet. Goodwill is an accounting entry that represents the extra amount paid above the fair value of what was purchased. If energy markets weaken or the deal performs below expectations, the company may have to write down billions of dollars of that goodwill, reducing reported earnings significantly even if no actual cash leaves the door.