Ameren expands MISO transmission footprint through multi-billion dollar project awards
The holding company leveraged formula ratemaking and securitization tools to fund grid expansion and the accelerated retirement of coal assets.
Ameren (AEE) expanded its regional transmission capacity and restructured its generation cost recovery across its Missouri and Illinois operations during the 2025 report year. The holding company manages its regulated footprint through Union Electric Company (MO), Ameren Illinois Company (IL), and Ameren Transmission Company of Illinois (IL).
Transmission investment drove the year's capital activity. Ameren Transmission Company of Illinois secured MISO long-range transmission projects with estimated costs of $1.8 billion for the first tranche and $1.3 billion for the second tranche. The company also added $220 million in competitive bid projects to its build-out. To support these assets, the company utilizes a forward-looking formula ratemaking framework. This structure includes an allowed base ROE supplemented by incentive adders of up to 50 basis points for RTO participation and an additional 50 basis points specifically for the Mark Twain line.
In Missouri, Union Electric Company managed the financial transition of its generation fleet. The company established a Variable Interest Entity in 2024 to issue securitized utility tariff bonds. This mechanism was designed to fund the accelerated retirement of the Rush Island Energy Center, shifting the cost recovery of the plant's closure into a securitized instrument. Union Electric also maintained its integration with the Midcontinent Independent System Operator through annual updates to the MISO FERC Electric Tariff, including docket ER26-1692-000.
Revenue streams remained concentrated across the two primary operating states. Union Electric reported electric operating revenues of $4.63 billion, while Ameren Illinois reported electric operating revenues of $2.97 billion.
Operational adjustments in Illinois focused on credit risk and revenue stability. Ameren Illinois employed bad debt riders to adjust rates based on the net write-offs of customer accounts receivable. This regulatory tool allows the utility to recover losses from uncollectible customer bills through the rate base rather than absorbing them as operational expenses.
The company's forward path is defined by the execution of its awarded MISO transmission projects and the ongoing servicing of the securitized bonds related to the Rush Island retirement. As Ameren Transmission Company of Illinois continues to operate the Illinois Rivers, Spoon River, and Mark Twain lines, the company remains positioned to capture incentive-based ROE through its FERC-regulated transmission assets.