Direct Answer
Ameren reports revenue across 4 business segments in its fiscal 2025 Form 10-K. Union Electric Company is the largest, with $4.8 billion of revenue (54% of the total), followed by Ameren Illinois Electric Distribution at $2.4 billion (27%).
How Does Ameren Make Money?
No single line supplies a majority of revenue: the largest, Union Electric Company, is 54%, which spreads Ameren's exposure across several demand drivers. Between fiscal 2024 and 2025, Union Electric Company grew fastest (+20.3%) and Ameren Illinois Gas slowest (+3.2%), so the revenue mix tilts toward Union Electric Company while that gap lasts.
| Segment | FY2025 revenue | FY2024 revenue | Share of revenue | Change |
|---|---|---|---|---|
| Union Electric Company | $4.8 billion | $4.0 billion | 54.1% | 20.3% |
| Ameren Illinois Electric Distribution | $2.4 billion | $2.1 billion | 27.2% | 14.6% |
| Ameren Illinois Gas | $968 million | $938 million | 11.0% | 3.2% |
| Ameren Transmission | $675 million | $637 million | 7.7% | 6.0% |
What Does Ameren Sell?
Ameren also breaks revenue down by product and service line, which shows what customers pay for rather than how management organizes the business.
| Product or service | FY2025 revenue | FY2024 revenue | Share of revenue | Change |
|---|---|---|---|---|
| Electricity | $7.7 billion | $6.5 billion | 87.1% | 17.2% |
| Natural Gas Reserves | $1.1 billion | $1.1 billion | 12.9% | 4.4% |
What the Segment Figures Do Not Show
The rows above add up to 100% of Ameren's reported revenue for fiscal 2025; the difference is intersegment eliminations, corporate revenue or items the company reports outside its segments. Segment definitions are management's choice and change when a company reorganizes, in which case it restates prior years in the next filing, so a multi-year comparison should use the figures from a single filing. Revenue shows where sales come from, not where profit or cash is earned: a small segment can carry most of the margin.
Where These Numbers Come From
Every figure on this page is a value Ameren reported in the segment note and revenue disclosures of its Form 10-K filed February 18, 2026 (accession 0001002910-26-000009), read from the SEC's Financial Statement Data Sets. The prior-year column is the comparative figure from that same filing, so it reflects any restatement for a change in segments. Category names are the company's own XBRL labels, lightly reformatted for reading.
Rows that only total other rows (for example a "Products" line beside the individual products) are left out so nothing is counted twice. This page is educational and describes reported history for fiscal 2025; it is not a forecast or a recommendation.
Frequently Asked Questions
What are Ameren's business segments?
In its fiscal 2025 Form 10-K, Ameren reports revenue for Union Electric Company, Ameren Illinois Electric Distribution, Ameren Illinois Gas and Ameren Transmission.
Which part of Ameren brings in the most revenue?
Union Electric Company, with $4.8 billion of revenue in fiscal 2025, or 54% of the total.
Where does Ameren report its segment results?
In the segment note to the financial statements in its Form 10-K, most recently filed February 18, 2026, alongside management's discussion of each segment's results.