Exelon

• 1. Introduction

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  Exelon Corporation is the largest regulated electric utility in the United States, serving approximately 10 million customers across six states and the District of Columbia. That number alone is remarkable. But behind it sits a story of mergers, nuclear accidents, political battles, and a corporate empire assembled piece by piece over more than two decades.

  How does a company become the backbone of power for an entire region? And what happens when that much infrastructure is held in a single set of hands? The answers begin in Chicago in the autumn of 2000, and they stretch through courthouses, regulatory hearings, and a radioactive water spill that stayed secret for four years.

• 2. A Merger in October

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  In October 2000, PECO Energy Company and Unicom Corporation completed a merger that created Exelon Corporation. PECO had been operating since 1902. Unicom, the parent of Commonwealth Edison, traced its roots to 1907. The two companies brought nearly a century of combined history into a single entity.

  Unicom had been based in Chicago, and the new company kept that city as its headquarters. The merger was guided by John Rowe, who had joined Unicom as CEO in 1998. Rowe would lead Exelon until 2012, eventually earning the distinction of being the longest-serving utility executive in the country.

  That longevity mattered. In an industry shaped by regulatory cycles and long-horizon capital planning, continuity at the top allowed Exelon to pursue an unusually aggressive expansion strategy. Rowe's tenure would span two major acquisitions, a failed merger attempt, and a string of controversies that tested the company's relationship with the public.

• 3. The Mergers That Shaped a Giant

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  On the 31st of July 2005, the Federal Energy Regulatory Commission gave Exelon the green light to merge with Public Service Enterprise Group, a New Jersey utility. The deal seemed set. But over the following 18 months, pressure mounted from community organizations, including New Jersey Citizen Action, which pushed the New Jersey Board of Public Utilities hard enough that both companies eventually walked away.

  Exelon pivoted. On the 12th of March 2012, it acquired Constellation Energy. The combined company now controlled more than 34 gigawatts of power generation. The fuel mix told its own story: 55% nuclear, 24% natural gas, 8% renewable including hydro, 7% oil, and 6% coal. Nuclear was not just part of Exelon's portfolio. It was the dominant force.

  Two years later, on the 30th of April 2014, Exelon announced the purchase of Pepco Holdings for $6.8 billion in an all-cash transaction. The deal met fierce opposition from community groups and from Washington D.C. Mayor Muriel Bowser. The District of Columbia Public Service Commission rejected it outright in August 2015. The companies appealed. On the 23rd of March 2016, after Exelon made concessions, the commission reversed course. The merger went through, and Exelon became the largest regulated utility in the United States by customer count and total revenue.

• 4. Six Utilities, One Owner

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  Commonwealth Edison, known as ComEd, is the largest of Exelon's six subsidiaries, serving 4 million electric customers across Illinois. PECO Energy, serving eastern Pennsylvania, adds 1.6 million electric customers and more than 500,000 natural gas customers.

  Baltimore Gas and Electric brings more than 1.25 million electric customers and more than 650,000 natural gas customers in Maryland. Pepco covers Washington D.C. and parts of Maryland, serving 842,000 electric customers in the capital and surrounding areas.

  The two smaller utilities cover thinner geography. Atlantic City Electric serves 545,000 customers in New Jersey. Delmarva Power operates across 5,000 square miles of Delaware and the Eastern Shore of Maryland, reaching 515,000 electric customers and providing natural gas to 130,000 customers in northern Delaware. Each subsidiary operates as a regulated utility, meaning its rates and investments are subject to state-level oversight rather than open market competition.

• 5. Tritium, Security Guards, and Fines

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  In 2005, Exelon paid a $602,000 fine after its Cromby Generating Station in Chester County, Pennsylvania exceeded permitted sulfur dioxide emission limits from April to October 2004.

  A more serious episode unfolded around the Braidwood Nuclear Generating Station, located 60 miles southwest of Chicago. The plant had spilled millions of gallons of water containing tritium, a radioactive form of hydrogen, multiple times over a decade. Exelon and Illinois state officials waited four years before disclosing the spills, finally acknowledging them in 2006. Exelon officials eventually apologized and described the risk from the leaks as "minimal," pointing to tritium levels in surrounding wells that fell below regulatory limits. The delay drew sharp criticism.

  In 2009, the Nuclear Regulatory Commission announced a plan to fine Exelon $65,000 after contracted security guards at the Peach Bottom Nuclear Generating Station, a two-reactor plant in Delta, Pennsylvania, were caught sleeping on the job. The incidents only came to light after a videotape was leaked to news media. Exelon terminated the contract with Wackenhut, the security firm involved, and moved to an in-house nuclear security operation.

  Not all the challenges were recent. In the 1970s, activists managed to delay the opening of nuclear power plants operated by PECO Energy, the predecessor company that would eventually anchor Exelon's founding merger.

• 6. Spinning Off a Nuclear Empire

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  On the 2nd of February 2022, Exelon completed the corporate spin-off of Constellation Energy, separating its power generation business into a standalone company. At the time of the split, Constellation was the largest operator of nuclear power plants in the United States and the largest non-governmental operator of nuclear power plants in the world.

  Constellation held full or majority ownership of 23 nuclear reactors across 14 nuclear power plants. Its total owned capacity reached approximately 35,500 megawatts. The spin-off restructured Exelon into a purely regulated utility business, shedding the competitive power generation side that had long defined the company's scale.

  The Earth Quaker Action Team, which had launched a campaign in 2015 to pressure PECO to expand its local solar purchases and create regional jobs, was one signal of the shifting expectations around energy companies. The generation side of the business faced different pressures than the transmission and distribution side. Separating them gave Constellation room to operate under different regulatory and market conditions, while the remaining Exelon focused on its 10 million regulated customers.

• 7. Political Reach and Public Money

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  Exelon channels political activity through its PAC, EXELONPAC. In the two-year period of 2021 and 2022, the PAC contributed $323,500 to federal candidates: $202,500 went to Democrats and $121,000 to Republicans. In 2022 alone, the company spent $2,878,000 on lobbying.

  Those numbers reflect the stakes. A company ranked 187th on the Fortune 500, with assets that in 2017 reached $116.7 billion and revenues that year of $33.5 billion, operates in a world where regulatory decisions can shift earnings by hundreds of millions of dollars. The merger battles over Pepco, the rejected deal with Public Service Enterprise Group, and the long fight with the D.C. Public Service Commission all demonstrated how central political relationships are to utility growth. Exelon's history is as much a story about regulators and public commissions as it is about power lines and transformers.