Exelon Corporation
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Company History
Founded 2000 in Chicago, Illinois
1882: Chicago Edison Company begins supplying electricity to downtown Chicago. 1881: Philadelphia Electric Company starts operations in Pennsylvania. These two utilities operated independently for over a century, building distribution infrastructure across their respective service territories through the industrialization of America, two world wars, and the postwar suburban expansion. The 2000 merger of PECO Energy and Unicom (parent of Commonwealth Edison) created Exelon Corporation — a combination that brought together the Philadelphia and Chicago utility legacies under a single holding company. The merged entity immediately ranked among the largest utilities in the country by customer count and rate base. The 2012 spin-off of Constellation Energy was an early signal of the pure-play regulated utility direction, though Constellation at that time retained significant unregulated nuclear generation. The 2016 acquisition of Pepco Holdings — a deal initially blocked by D.C. Regulators before eventually receiving approval — added the Mid-Atlantic service territory and extended the geographic corridor that defines Exelon's footprint. The complete separation of Constellation in 2022 completed the transformation that the 2012 spin-off had started. The Exelon that remains is a distribution-focused regulated utility with no exposure to commodity power markets — a structure that institutional investors in regulated utilities explicitly prefer.
Exelon possesses a deep, corporate lineage, tracing its roots to the dawn of commercial electricity and the legendary ambition of the man who invented the modern utility business model: Samuel Insull. The modern conglomerate is the product of a 2000 merger between PECO Energy (Philadelphia) and Unicom (the parent company of Commonwealth Edison in Chicago). The foundational DNA of the company lies with Commonwealth Edison (ComEd), founded in 1907 by Samuel Insull. Insull was originally Thomas Edison's personal secretary, but he moved to Chicago and built an unprecedented energy empire. Insull was a financial visionary. While other early utilities operated small, inefficient neighborhood power plants, Insull realized that electricity was a natural monopoly. He bought up all the small, fragmented power companies in Chicago and consolidated them. His foundational breakthrough was the concept of the 'load factor.' He realized that if he built efficient, centralized power plants, he needed to sell electricity 24 hours a day to pay off the capital cost. He pushed for the electrification of streetcar systems (which ran during the day) and industrial factories (which ran at night). Insull invented the capital-intensive, regulated monopoly model that defines the entire American utility industry today. Although his holding company empire tragically collapsed during the Great Depression, the foundational physical grid and the fundamental economic architecture he built in Chicago remain the core of the modern Exelon corporation.
The Chicago Edison Company is founded, later evolving into Commonwealth Edison (ComEd) under the leadership of Samuel Insull, establishing the foundation for modern electric utility distribution in the Midwest.
The Philadelphia Electric Company is established to provide reliable power to the rapidly growing industrial hub of Philadelphia, building a dense network of wires and substations that would become the backbone of the region's economy.
PECO Energy Company and Commonwealth Edison execute a landmark, $34 billion merger of equals to form Exelon Corporation, creating a diversified energy conglomerate with significant regulated and competitive assets.
Exelon spins off its competitive power generation business into a separate, publicly traded company named Constellation Energy, allowing Exelon to focus more heavily on its regulated utility operations, though the two would later re-merge briefly before a final split.
Following a lengthy regulatory battle, Exelon completes the $6.8 billion acquisition of Pepco Holdings, instantly expanding its regulated footprint into Washington D.C., Maryland, and Delaware, and solidifying its position as the largest regulated utility in the United States by customer count.
The state of Illinois passes the Future Energy Jobs Act, providing a stable, multi-year regulatory framework for ComEd to recover its investments in grid modernization and energy efficiency, marking a turning point in the company’s relationship with Illinois regulators.
Exelon completes the strategic, tax-free spin-off of its competitive power generation business, Constellation Energy, transforming Exelon into a pure-play regulated electric and gas utility and eliminating all merchant power market exposure.
Calvin Butler Jr. assumes the role of President and Chief Executive Officer, initiating a comprehensive strategic focus on grid resilience, extreme weather hardening, and the execution of the company's multi-billion-dollar capital expenditure program.
Exelon begins the operational and financial restructuring required to comply with the Climate and Equitable Jobs Act in Illinois, positioning ComEd as the central architect of the state's aggressive decarbonization and grid modernization mandates.
Exelon reported $24.258 billion in FY2025 revenue and $2.768 billion in net income available to common shareholders while continuing regulated grid and utility investment.
In a transformative merger that reshaped the American energy landscape, Exelon acquired Constellation Energy Group. This deal primarily added Baltimore Gas and Electric (BGE) to Exelon's portfolio of regulated utilities, establishing a vital foothold in the lucrative Mid-Atlantic market. More importantly at the time, the merger combined Exelon's low-cost nuclear generation fleet with Constellation's industry-leading wholesale power marketing and retail customer-facing business. This created a colossal, vertically integrated energy powerhouse capable of selling electricity directly to residential and commercial customers across the country, effectively hedging Exelon's generation output against fluctuating wholesale market prices.
Seeking to reduce its exposure to volatile wholesale energy prices, Exelon expanded its regulated utility footprint by acquiring Pepco Holdings. This transaction brought three major regional utilities—Potomac Electric Power Company (Pepco), Delmarva Power (DPL), and Atlantic City Electric (ACE)—under the Exelon corporate umbrella. The deal expanded Exelon's customer base by nearly two million, cementing its status as the largest regulated utility operator in the United States and significantly shifting the company's overall revenue mix toward predictable, regulated transmission and distribution operations.
Since its establishment in 2000, Exelon Corporation expanded from an early-stage venture into a recognized leader in Regulated Electric and Gas Utilities, overcoming key market challenges.
Over its history, Exelon Corporation executed decisive strategic pivots toward scalable monetization and digital distribution, securing its current market leadership.
By continually modernizing operations and embracing workflow automation, Exelon Corporation maintains resilience through changing technological and economic cycles.