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Property And Plant, Net | 12 Months Ended
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Dec. 31, 2025
Property, Plant and Equipment [Abstract] |
PROPERTY AND PLANT, NET | PROPERTY, PLANT, AND EQUIPMENT, NET The following table presents components of “Property, plant, and equipment, net” at December 31, 2025 and 2024:
|  | Ameren Missouri |  | Ameren Illinois |  | Other |  | Ameren
2025 |  |  |  |  |  |  |  |
Property, plant, and equipment at original cost(a): |  |  |  |  |  |  |  |
Electric generation: |  |  |  |  |  |  |  |
Coal(b) |  | $ | 3,640 |  |  | $ | — |  |  | $ | — |  |  | $ | 3,640 |
Natural gas |  | 948 |  |  | — |  |  | — |  |  | 948 |
Nuclear |  | 6,255 |  |  | — |  |  | — |  |  | 6,255 |
Renewable(c) |  | 3,072 |  |  | 19 |  |  | — |  |  | 3,091 |
Electric distribution |  | 10,205 |  |  | 8,758 |  |  | — |  |  | 18,963 |
Electric transmission |  | 2,479 |  |  | 6,247 |  |  | 2,184 |  |  | 10,910 |
Natural gas |  | 837 |  |  | 4,642 |  |  | — |  |  | 5,479 |
Other(d) |  | 2,132 |  |  | 1,412 |  |  | 40 |  |  | 3,584 |
|  | 29,568 |  |  | 21,078 |  |  | 2,224 |  |  | 52,870 |
Less: Accumulated depreciation and amortization |  | 11,090 |  |  | 5,219 |  |  | 260 |  |  | 16,569 |
|  | 18,478 |  |  | 15,859 |  |  | 1,964 |  |  | 36,301 |
Construction work in progress: |  |  |  |  |  |  |  |
Nuclear fuel in progress |  | 194 |  |  | — |  |  | — |  |  | 194 |
Other |  | 1,932 |  |  | 708 |  |  | 178 |  |  | 2,818 |
Property, plant, and equipment, net |  | $ | 20,604 |  |  | $ | 16,567 |  |  | $ | 2,142 |  |  | $ | 39,313 |
2024 |  |  |  |  |  |  |  |
Property, plant, and equipment at original cost(a): |  |  |  |  |  |  |  |
Electric generation: |  |  |  |  |  |  |  |
Coal(b) |  | $ | 3,556 |  |  | $ | — |  |  | $ | — |  |  | $ | 3,556 |
Natural gas |  | 938 |  |  | — |  |  | — |  |  | 938 |
Nuclear |  | 5,931 |  |  | — |  |  | — |  |  | 5,931 |
Renewable(c) |  | 2,901 |  |  | 19 |  |  | — |  |  | 2,920 |
Electric distribution |  | 9,469 |  |  | 8,160 |  |  | — |  |  | 17,629 |
Electric transmission |  | 2,406 |  |  | 5,725 |  |  | 2,031 |  |  | 10,162 |
Natural gas |  | 776 |  |  | 4,421 |  |  | — |  |  | 5,197 |
Other(d) |  | 2,427 |  |  | 1,770 |  |  | 260 |  |  | 4,457 |
|  | 28,404 |  |  | 20,095 |  |  | 2,291 |  |  | 50,790 |
Less: Accumulated depreciation and amortization |  | 10,875 |  |  | 5,184 |  |  | 436 |  |  | 16,495 |
|  | 17,529 |  |  | 14,911 |  |  | 1,855 |  |  | 34,295 |
Construction work in progress: |  |  |  |  |  |  |  |
Nuclear fuel in progress |  | 268 |  |  | — |  |  | — |  |  | 268 |
Other |  | 991 |  |  | 619 |  |  | 131 |  |  | 1,741 |
Property, plant, and equipment, net |  | $ | 18,788 |  |  | $ | 15,530 |  |  | $ | 1,986 |  |  | $ | 36,304 |
(a)The estimated lives for each asset group are as follows: 5 to 72 years for electric generation, excluding Ameren Missouri’s hydroelectric generating assets, which have useful lives of up to 150 years; 20 to 80 years for electric distribution; 50 to 75 years for electric transmission; 15 to 80 years for natural gas; and 2 to 55 years for other. (b)Includes $30 million of oil-fired generation at December 31, 2025 and 2024. (c)Renewable includes hydroelectric, wind, solar, and methane gas generation facilities. (d)Other property, plant, and equipment includes assets used to support electric distribution, electric transmission, and natural gas services. Capitalized software costs are classified within “Property, Plant, and Equipment, Net” on the balance sheet and are amortized on a straight-line basis over the expected period of benefit, ranging from 2 to 15 years, with the amortization expense included in “Depreciation and amortization” on the statement of income. Deferred cloud implementation costs are classified within “Other Assets” on the balance sheet and are amortized on a straight-line basis over the term of the associated hosting arrangement, ranging from 5 to 15 years, with the amortization expense included in “Other operations and maintenance” on the statement of income. The following table presents the amortization expense, gross carrying value, and related accumulated amortization of capitalized software and deferred cloud implementation costs by year:
|  | Amortization Expense |  | Gross Carrying Value |  | Accumulated Amortization
|  | 2025 | 2024 | 2023 |  | 2025 | 2024 |  | 2025 | 2024
Capitalized software costs: |  |  |  |  |  |  |  |  |  |
Ameren |  | $ | 222 |  | $ | 224 |  | $ | 212 |  |  | $ | 1,174 |  | $ | 1,996 |  |  | $ | (572) |  | $ | (1,348) |
Ameren Missouri |  | 113 |  | 118 |  | 114 |  |  | 562 |  | 881 |  |  | (290) |  | (567) |
Ameren Illinois |  | 101 |  | 100 |  | 92 |  |  | 570 |  | 867 |  |  | (261) |  | (552) |
Deferred cloud implementation costs: |  |  |  |  |  |  |  |  |  |
Ameren |  | $ | 19 |  | $ | 20 |  | $ | 17 |  |  | $ | 142 |  | $ | 157 |  |  | $ | (59) |  | $ | (71) |
Ameren Missouri |  | 8 |  | 9 |  | 8 |  |  | 63 |  | 71 |  |  | (28) |  | (32) |
Ameren Illinois |  | 10 |  | 10 |  | 9 |  |  | 76 |  | 82 |  |  | (29) |  | (36) |
Annual amortization expense for capitalized software classified as in service as of December 31, 2025, is estimated to be as follows:
|  | 2026 |  | 2027 |  | 2028 |  | 2029 |  | 2030
Ameren |  | $ | 198 |  |  | $ | 152 |  |  | $ | 98 |  |  | $ | 63 |  |  | $ | 32 |
Ameren Missouri |  | 96 |  |  | 73 |  |  | 46 |  |  | 28 |  |  | 14 |
Ameren Illinois |  | 96 |  |  | 73 |  |  | 49 |  |  | 32 |  |  | 17 |

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