Overview
On October 30, 2026, the Justice Department’s Antitrust Division issued a statement regarding its investigation of the acquisition of Cogentrix Energy ("Cogentrix") by Vistra Corp. ("Vistra"). The statement provides a useful indication of how the Antitrust Division is screening electricity-generation transactions: it confirms that (1) the Antitrust Division may continue investigating a transaction even following Federal Energy Regulatory Commission ("FERC") approval; and (2) the Division is applying the analytical framework set out in Constellation-Calpine, including potentially narrow geographic and narrow product markets.
In its statement, the Antitrust Division made clear that it will review and may challenge electricity-generation mergers even where FERC has approved. During FERC’s review, the Internal Market Monitor ("IMM") cautioned against relying heavily on HHI calculations where the combined portfolio following the transaction "would be pivotal in a substantial share of real-time intervals, including the majority of high-load hours." Without prompting from FERC, Vistra decided to sell its Casco Bay Energy facility, apparently to satisfy FERC concerns. After that divestiture, FERC approved the transaction. The Antitrust Division nevertheless continued investigating, raising concerns about the combination of the parties’ gas-fired power plants in ISO New England ("ISO-NE"), the organization that operates the regional electricity grid and wholesale electricity markets in New England. To address these concerns, Vistra and Cogentrix decided to divest Cogentrix’s gas-fired combined-cycle power plant in Rumford. Vistra closed its acquisition of Cogentrix shortly after the Antitrust Division’s statement, indicating that the Antitrust Division’s review had ended.
Thus, FERC’s approval was not automatically sufficient to address the Antitrust Division’s concerns: companies need to ensure they are addressing both agencies’ interests. The agencies’ different outcomes appear to reflect their distinct analytical approaches: FERC’s approval rested on the transaction’s satisfaction of FERC’s established competitive screens after considering the Casco Bay divestiture, whereas the Antitrust Division continued examining whether the particular combination of gas-fired plants could give the merged company the ability or incentive to raise prices in ISO-NE.
Substantively, the Antitrust Division stated that its investigation of the transaction "followed the framework for evaluating electricity mergers described in the Division’s 2025 settlement complaint and competitive impact statement regarding Constellation Energy Corp.’s acquisition of Calpine Corp." By expressly adopting the Constellation-Calpine investigation as a framework for the electricity industry, the Antitrust Division signals how it will define markets and screen future transactions.
With respect to geographic market, the Antitrust Division’s geographic market in the Constellation-Calpine complaint was a prominent theme. The alleged geographic market there was the narrower "PJM Coastal Mid-Atlantic," dividing PJM Interconnection ("PJM"), the Regional Transmission Organization ("RTO") serving parts of the Midwest and Mid-Atlantic, into narrower geographic sub-units than RTO-wide. In support of this narrower geographic market, the Antitrust Division relied on transmission constraints to define narrow geographic markets within wholesale power regions. In its Vistra-Cogentrix statement, the Antitrust Division did not say whether it looked as a narrower part of ISO-NE or considered the entire ISO-NE as the geographic market, but its express reference to Constellation-Calpine suggests that it might have chosen a narrower market.
Another notable aspect of the Constellation-Calpine complaint was the Antitrust Division’s focus on the role of flexible generating assets, particularly mid-merit and peaking units. Mid-merit units, such as combined-cycle natural-gas plants, can generally start or adjust their output more quickly than baseload plants, while peaking units typically operate during periods of high demand and can be turned on and off relatively quickly. The Department of Justice ("DOJ") alleged that control over these flexible assets could make it easier for a generator to withhold output, require the system operator to dispatch a higher-priced unit, and thereby increase the price received by the generator’s other plants. That competitive-effects theory operated within DOJ’s alleged product markets: the sale of wholesale electricity during particular hourly day-ahead or five-minute real-time auction intervals.
The analysis for both geographic market, product market, and competitive effects shows that the Antitrust Division is looking at narrow markets at a more granular level than the RTO or ISO level. Industry participants should expect the agency might revisit and update historical congestion analyses and continue to argue for localized geographic markets where recurring constraints produce price separation and for narrower product markets focused on gas-fired peaking units in future deal evaluations.
