OVERVIEW
Ameren Executive Summary
Operations
In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business segment's long-lived assets. This determination resulted from Ameren's analysis of the current and projected future financial condition of its Merchant Generation business, including the need to fund Genco debt maturities beginning in 2018, and its conclusion that this business was no longer a core component of its future business strategy. The volatility of earnings and cash flows of the Merchant Generation business, as well as the high degree of uncertainty regarding future returns on incremental capital invested in this business, are not in alignment with Ameren's current strategy. Ameren's decision to exit the business follows a trend of decreasing earnings and cash flows from the Merchant Generation business since 2008. Ameren's date and method of exit from the Merchant Generation business is currently uncertain with a sale or restructuring possible. Senior management and Ameren's board of directors are focused on maximizing the overall benefit to Ameren consistent with its legal obligations. While working to exit the Merchant Generation business, Ameren remains focused on its rate-regulated utilities, including growing investments in jurisdictions with constructive regulatory frameworks. Ameren continues to seek modern, constructive regulatory frameworks, which provide timely cash flows and a reasonable opportunity to earn fair returns on investments that are in the best long-term interest of Ameren's customers. These frameworks support Ameren's rate-regulated businesses' ability to obtain cash on a timelier basis, to reinvest in energy infrastructure and also attract capital on terms that facilitate timely investments to modernize their aging infrastructure. In December 2012, the MoPSC issued an order approving an increase for Ameren Missouri in annual revenues for electric service of $260 million. These new rates became effective on January 2, 2013. The MoPSC's December 2012 electric rate order improved Ameren Missouri's regulatory framework for energy efficiency programs as well as authorized the implementation of a new storm restoration cost tracking mechanism.
In 2012, Ameren Illinois elected to participate in the IEIMA's performance-based formula ratemaking framework. The IEIMA was designed to promote investment in electric grid modernization and create jobs through the establishment of formula ratemaking for electric delivery service. Ameren Illinois believes the ICC has incorrectly implemented the IEIMA in both of its 2012 electric delivery service rate orders. As a result, Ameren Illinois has appealed both 2012 electric delivery service rate orders to the Appellate Court of the Fourth District of Illinois and is also seeking a legislative solution to address the ICC's

implementation of the IEIMA. Additionally, in January 2013, Ameren Illinois filed a request with the ICC to increase its annual revenues for natural gas delivery service by $50 million. This request was based on a 2014 future test year.
Ameren continues to proceed with its plans to increase its investment in FERC-regulated electric transmission. In 2013, for both Ameren Illinois and ATXI, transmission rates will be updated annually based on a forward-looking calculation with a revenue requirement reconciliation. Ameren expects to invest a total of approximately $2.2 billion in FERC-regulated transmission projects over the next five years. The Ameren Illinois portion of that total, approximately $1 billion, is for projects focused on local load growth and reliability needs. ATXI, through its construction of three MISO-approved regional multi-value electric transmission projects, expects to invest approximately $1.2 billion over the next five years. In November 2012, ATXI filed a request with the ICC for a certificate of public convenience and necessity for the Illinois Rivers project. Once ATXI receives the certificate of public convenience and necessity, it can begin to acquire right of way for the Illinois Rivers project. A full range of construction activities for the Illinois Rivers project is expected to begin in 2014. Earnings
Ameren reported a net loss of $974 million, or $4.01 per share, for 2012 compared with net income of $519 million, or $2.15 per share, in 2011. The main factor contributing to the net loss in 2012, compared with net income in 2011, was the 2012 impairments of Merchant Generation's long-lived assets resulting from Ameren's determination in December 2012 that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously useful lives of that business segment's long-lived assets, coupled with the sharp decline in the market price for power in the first quarter of 2012. The decline in Merchant Generation earnings also reflected lower power prices and higher fuel costs. Ameren's earnings also decreased in 2012, compared with 2011, because of a decline in Ameren Illinois' earnings primarily due to the impacts of implementing the IEIMA's formula ratemaking in 2012, including a lower allowed return on equity and required nonrecoverable contributions, as well as lower natural gas sales volumes as a result of warmer 2012 winter temperatures. Summer weather was much warmer than normal in 2012, but similar to 2011. The earnings declines in the Merchant Generation and Ameren Illinois segments were partially offset by increased Ameren Missouri earnings due primarily to the full year effect of the 2011 electric rate increase as well as lower operations and maintenance expense reflecting the absence of a refueling outage at the Callaway energy center in 2012, decreased labor costs primarily due to staff reductions resulting from the 2011 voluntary separation plan, and reduced major storm-related costs. Ameren Missouri's 2012 earnings, compared to 2011 earnings, also benefited from a favorable 2012 FERC order related to a disputed power purchase agreement that expired in 2009 and the absence of a 2011 charge to earnings related to the FAC. These positive Ameren Missouri factors were partially offset by higher

depreciation expense and lower electric sales volumes due to warmer 2012 winter temperatures.
Liquidity
Cash flows from operations of $1.7 billion were used to pay dividends to common stockholders of $382 million and to fund capital expenditures of $1.2 billion. At December 31, 2012, Ameren, on a consolidated basis, had available liquidity, in the form of cash on hand and amounts available under existing credit agreements, of approximately $2.3 billion, which was a $100 million increase from the amount of available liquidity at December 31, 2011. Capital Spending
From 2013 through 2017, Ameren's cumulative capital spending is projected to range between $7.4 billion and $9.5 billion. Much of this spending is at Ameren's rate-regulated utilities, including a total of approximately $1.2 billion at ATXI to invest in its electric transmission assets as discussed above. The Merchant Generation segment's capital spending is expected to be up to $385 million from 2013 through 2017, assuming Ameren continues to own the Merchant Generation energy centers for the entire period. General
Ameren, headquartered in St. Louis, Missouri, is a public utility holding company under PUHCA 2005, administered by FERC. Ameren's primary assets are its equity interests in its subsidiaries. Ameren's subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. These subsidiaries operate, as the case may be, rate-regulated electric generation, transmission, and distribution businesses, rate-regulated natural gas transmission and distribution businesses, and merchant electric generation businesses. Dividends on Ameren's common stock and the payment of other expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren's principal subsidiaries are listed below. See Note 1 - Summary of Significant Accounting Policies under Part II, Item 8, of this report for a detailed description of our principal subsidiaries.
• Ameren Missouri operates a rate-regulated electric generation, transmission, and distribution business, and a rate-regulated natural gas transmission and distribution business in Missouri.

• Ameren Illinois operates a rate-regulated electric and natural gas transmission and distribution business in Illinois.

• AER consists of non-rate-regulated operations, including Genco, AERG, Marketing Company, and through Genco, an 80% ownership interest in EEI, which Ameren consolidates for financial reporting purposes.

In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business's long-lived assets. This determination resulted from Ameren's analysis of the current and projected future

financial condition of its Merchant Generation business segment, including the need to fund Genco debt maturities beginning in 2018, and its conclusion that this business segment is no longer a core component of its future business strategy. In consideration of this determination, Ameren has begun planning to reduce, and ultimately eliminate, the Merchant Generation business segment's, including Genco's, reliance on Ameren's financial support and shared services support. Furthermore, Ameren recorded a noncash long-lived asset impairment charge to reduce the carrying values of the Merchant Generation energy centers, except for the Joppa coal-fired energy center, to their estimated fair values. See Note 17 - Impairment and Other Charges under Part II, Item 8, for additional information. Ameren's date and method of exit from the Merchant Generation business is currently uncertain. Exit strategies may include the sale of all or parts of the Merchant Generation business and the restructuring of all or a portion of Ameren's equity position in Genco. Ameren's Merchant Generation long-lived assets have not been classified as held-for-sale under authoritative accounting guidance as all criteria to qualify for that presentation were not met as of December 31, 2012. Specifically, Ameren did not consider it probable that a disposition would occur within one year.
On October 1, 2010, Ameren, CIPS, CILCO, IP, AERG and AER completed a two-step corporate internal reorganization. The first step of the reorganization was the Ameren Illinois Merger. The second step of the reorganization involved the distribution of AERG stock from Ameren Illinois to Ameren and the subsequent contribution by Ameren of the AERG stock to AER. Ameren Illinois segregated AERG's operating results and cash flows and presented them separately as discontinued operations in its consolidated statement of income and consolidated statement of cash flows, respectively, for all periods presented prior to October 1, 2010, in this report. See Note 16 - 2010 Corporate Reorganization under Part II, Item 8, for additional information.
The financial statements of Ameren and Ameren Illinois are prepared on a consolidated basis and therefore include the accounts of their respective majority-owned subsidiaries. Ameren Illinois' financial statements are consolidated because Ameren Illinois included AERG in its statements of income and cash flows during 2010. Ameren Missouri has no subsidiaries, and therefore its financial statements are not prepared on a consolidated basis. All significant intercompany transactions have been eliminated. All tabular dollar amounts are in millions, unless otherwise indicated.
In addition to presenting results of operations and earnings amounts in total, we present certain information in cents per share. These amounts reflect factors that directly affect Ameren's earnings. We believe that this per share information helps readers to understand the impact of these factors on Ameren's earnings per share. All references in this report to earnings per share are based on average diluted common shares outstanding.
RESULTS OF OPERATIONS
Our results of operations and financial position are affected

by many factors. Weather, economic conditions, and the actions of key customers or competitors can significantly affect the demand for our services. Our results are also affected by seasonal fluctuations: winter heating and summer cooling demands. The vast majority of Ameren's revenues are subject to state or federal regulation. This regulation has a material impact on the prices we charge for our services. Merchant Generation sales are also subject to market conditions for power. We principally use coal, nuclear fuel, natural gas, methane gas, and oil for fuel in our operations. The prices for these commodities can fluctuate significantly because of the global economic and political environment, weather, supply and demand, and many other factors. We have natural gas cost recovery mechanisms for our Illinois and Missouri natural gas delivery service businesses, a purchased power cost recovery mechanism for our Illinois electric delivery service business, and a FAC for our Missouri electric utility business. Ameren Illinois' electric delivery service utility business, pursuant to the IEIMA, conducts an annual reconciliation of the revenue requirement necessary to reflect the actual costs incurred in a given year with the revenue requirement that was in effect for that year, with recoveries from or refunds to customers in a subsequent year. Included in Ameren Illinois' revenue requirement reconciliation is a formula for the return on equity, which is equal to the average of the monthly yields of 30-year United States treasury bonds plus 590 basis points for 2012 and 580 basis points thereafter. Therefore, Ameren Illinois' annual return on equity will be directly correlated to yields on United States treasury bonds. Fluctuations in interest rates and conditions in the capital and credit markets also affect our cost of borrowing and our pension and postretirement benefits costs. We employ various risk management strategies to reduce our exposure to commodity risk and other risks inherent in our business. The reliability of our energy centers and transmission and distribution systems and the level of purchased power costs, operations and maintenance costs, and capital investment are key factors that we seek to control to optimize our results of operations, financial position, and liquidity.
Earnings Summary
Net loss attributable to Ameren Corporation was $974 million, or $4.01 per share, for 2012. Net income attributable to Ameren Corporation was $519 million, or $2.15 per share, for 2011, and $139 million, or $0.58 per share, for 2010. 2012 versus 2011
The net loss attributable to Ameren Corporation in 2012 was primarily caused by a net loss in the Merchant Generation segment of $1.516 billion in 2012. The Merchant Generation segment reported net income of $45 million in 2011. Net income attributable to Ameren Corporation in 2012 decreased in the Ameren Illinois Segment by $52 million from 2011 and increased in the Ameren Missouri segment by $129 million from 2011.
Compared with 2011 earnings per share, 2012 earnings were unfavorably affected by:
• the 2012 impairments of Merchant Generation's long-lived assets resulting from Ameren's determination in December

2012 that it intends to, and it is probable that it will, exit its Merchant Generation segment before the end of the previously estimated useful lives of that business segment's long-lived assets, coupled with the sharp decline in the market price of power in the first quarter of 2012 ($6.42 per share);
• lower electric margins in the Merchant Generation segment, largely due to reduced generation volumes caused by lower market prices for power as well as higher fuel and related transportation costs (34 cents per share);

• a reduction in Ameren Illinois' electric earnings primarily caused by a lower allowed return on equity under electric delivery service formula ratemaking and required donations pursuant to the IEIMA (17 cents per share);

• reduced electric and natural gas demand as a result of warmer 2012 winter temperatures (estimated at 7 cents per share); and

• reduced rate-regulated retail sales volumes, excluding the effects of abnormal weather, as sales volumes declined due to continued economic pressure, energy efficiency measures, and customer conservation efforts, among other items (2 cents per share).

Compared with 2011 earnings per share, 2012 earnings were favorably affected by:
• the absence in 2012 of charges recorded in 2011 at Ameren Missouri for the MoPSC's July 2011 disallowance of costs of enhancements relating to the rebuilding of Ameren Missouri's Taum Sauk energy center in excess of amounts recovered from property insurance and at Merchant Generation for the closure of the Meredosia and Hutsonville energy centers (32 cents per share);

• higher utility rates at Ameren Missouri and Ameren Illinois. Ameren Missouri's electric rates increased pursuant to an order issued by the MoPSC, which became effective in July 2011. The favorable impact of the Ameren Missouri rate increase on earnings was reduced by the increased regulatory asset amortization directed by the rate order. Ameren Illinois' natural gas rates increased pursuant to an order issued by the ICC, which became effective in mid-January 2012 (22 cents per share);

• the absence in 2012 of a Callaway energy center refueling and maintenance outage (11 cents per share);

• reduction in operations and maintenance expenses at both Ameren Missouri and Merchant Generation energy centers due to fewer outages and a reduction in employees (10 cents per share);

• the impact of fewer major storms on operations and maintenance expenses (9 cents per share);

• a reduction in Ameren Missouri's purchased power expense and an increase in interest income, each as a result of a FERC-ordered refund received in 2012 from Entergy for a power purchase agreement that expired in 2009 (7 cents per share);

• the absence in 2012 of a 2011 charge associated with voluntary separation offers to eligible Ameren Missouri and Ameren Services employees (7 cents per share);

• the absence in 2012 of a reduction in Ameren Missouri's

revenues as a result of the MoPSC's April 2011 FAC prudence review order covering the period from March 1, 2009, to September 30, 2009, which resulted in Ameren Missouri recording an obligation to refund to its electric customers the earnings associated with certain previously recognized sales (5 cents per share); and
• a decrease in Merchant Generation depreciation and amortization expense due to the asset impairments recorded in 2012, a change in 2011 in the estimates relating to asset retirement obligations, and the closure of the Meredosia and Hutsonville energy centers at the end of 2011, which was partially offset by an increase in Ameren Missouri depreciation and amortization expense caused primarily by the installation of scrubbers at the Sioux energy center (4 cents per share).

The cents per share information presented above is based on average shares outstanding in 2011.
2011 versus 2010
Net income attributable to Ameren Corporation increased $380 million, and earnings per share increased $1.57 in 2011 compared with 2010. The Merchant Generation segment reported net income attributable to Ameren Corporation of $45 million in 2011, compared with a $409 million net loss in 2010. Net income attributable to Ameren Corporation decreased in the Ameren Missouri segment and Ameren Illinois Segment by $77 million and $15 million, respectively, in 2011 compared with 2010.
Compared with 2010 earnings per share, 2011 earnings were favorably affected by:
• reduced impairment and other charges in the Merchant Generation segment, offset in part by a charge to earnings related to the MoPSC's July 2011 disallowance of costs of enhancements relating to the rebuilding of the Taum Sauk energy center in excess of amounts recovered from property insurance ($1.87 per share);

• higher Ameren Missouri electric rates pursuant to orders issued by the MoPSC, which became effective in June 2010 and in July 2011, as well as higher Ameren Missouri natural gas rates pursuant to a MoPSC order, which became effective in late February 2011. The impact of the Ameren Missouri electric rate increases on earnings was reduced by the adoption of life span depreciation methodology, recognition in 2010 of regulatory assets for previously expensed costs in the prior-year period, and increased regulatory asset amortization as directed by the rate orders (17 cents per share). These amounts exclude the unfavorable impact of the charge to earnings related to the MoPSC's disallowance of Taum Sauk rebuilding costs discussed above;

• lower interest expense, primarily due to the maturity and repayment of $200 million of Merchant Generation's senior secured notes in November 2010, the redemption of $66 million of Ameren Missouri's subordinated deferrable interest debentures in September 2010, Ameren Illinois' redemptions of $150 million of senior secured notes and $40 million of

first mortgage bonds in June 2011 and September 2010, respectively, and a reduction in borrowings under credit facility agreements (12 cents per share);
• higher Ameren Illinois electric rates pursuant to orders issued by the ICC in 2010 (6 cents per share);

• the absence in 2011 of a charge for the impact on deferred taxes from changes in federal health care laws (6 cents per share);

• the absence in 2011 of charges recorded in 2010 for cancelled or unrecoverable projects at Ameren Missouri (6 cents per share);

• a reduction in operations and maintenance expense related to plant maintenance, primarily at Ameren Missouri, as fewer costs were incurred for major outages at coal-fired energy centers because the scope of the outages in 2011 was not as extensive as the scope of the outages conducted in 2010 (5 cents per share); and

• reduction in expense as a result of disciplined cost management efforts to align spending with regulatory outcomes and economic conditions.

Compared with 2010 earnings per share, 2011 earnings were unfavorably affected by:
• lower electric margins in the Merchant Generation segment, largely due to lower realized revenue per megawatthour sold and higher fuel and related transportation costs (21 cents per share). This amount excludes the unfavorable impacts of net unrealized MTM activity discussed below;

• reduced rate-regulated retail sales volumes, excluding the effects of abnormal weather, as sales volumes declined due to continued economic pressure, energy efficiency measures, and customer conservation efforts as well as lower wholesale sales at Ameren Missouri due to a reduction in customers and the expiration of favorably priced contracts, among other items (15 cents per share);

• unrealized net losses on MTM activity primarily related to nonqualifying power hedges and fuel-related contracts as well as unfavorable changes in the market value of investments used to support Ameren's deferred compensation plans (10 cents per share);

• the impact of weather conditions on electric and natural gas demand (estimated at 10 cents per share);

• increased operations and maintenance expenses as a result of major storms in 2011 (9 cents per share);

• a reduction in allowance for equity funds used during construction reflecting the 2010 completion of two scrubbers at Ameren Missouri's Sioux energy center (8 cents per share);

• increased operations and maintenance expenses associated with voluntary separation offers to eligible Ameren Missouri and Ameren Services employees during 2011 (7 cents per share);

• a reduction in revenues resulting from the MoPSC's April 2011 order with respect to its FAC review for the period from March 1, 2009, to September 30, 2009, as discussed above. See Note 2 - Rate and Regulatory Matters under Part II, Item 8, of this report for additional information (5 cents per share); and

• an increase in depreciation and amortization expense caused primarily by the installation of scrubbers at Ameren Missouri's Sioux energy center as well as other capital additions (4 cents per share).

The cents per share information presented above is based on average shares outstanding in 2010.

For additional details regarding the Ameren Companies' results of operations, including explanations of Margins, Other Operations and Maintenance Expenses, Impairment and Other Charges, Depreciation and Amortization, Taxes Other Than Income Taxes, Other Income and Expenses, Interest Charges, and Income Taxes, see the major headings below.

Below is a table of income statement components by segment for the years ended December 31, 2012, 2011, and 2010:

                                                                                     Other /
                               Ameren             Ameren            Merchant       Intersegment
           2012               Missouri       Illinois Segment      Generation      Eliminations       Total
Electric margins            $     2,340     $          1,034     $        518     $        (11 )   $    3,881
Natural gas margins                  75                  378                -               (1 )          452
Other revenues                        1                    -                -               (1 )            -
Other operations and
maintenance                        (827 )               (684 )           (259 )             18         (1,752 )
Impairment and other
charges                               -                    -           (2,578 )              -         (2,578 )
Depreciation and
amortization                       (440 )               (221 )           (102 )            (12 )         (775 )
Taxes other than income
taxes                              (304 )               (130 )            (25 )             (9 )         (468 )
Other income and (expenses)          49                  (10 )             (1 )             (4 )           34
Interest charges                   (223 )               (129 )            (95 )             (1 )         (448 )
Income (taxes) benefit             (252 )                (94 )          1,019                7            680
Net income (loss)                   419                  144           (1,523 )            (14 )         (974 )
Noncontrolling interest and
preferred dividends                  (3 )                 (3 )              7               (1 )            -
Net income (loss)
attributable to Ameren
Corporation                 $       416     $            141     $     (1,516 )   $        (15 )   $     (974 )
           2011
Electric margins            $     2,252     $          1,087     $        668     $        (10 )   $    3,997
Natural gas margins                  79                  354                -               (2 )          431
Other revenues                        5                    1                3               (9 )            -
Other operations and
maintenance                        (934 )               (640 )           (285 )             39         (1,820 )
Impairment and other
charges                             (89 )                  -              (37 )              1           (125 )
Depreciation and
amortization                       (408 )               (215 )           (143 )            (19 )         (785 )
Taxes other than income
taxes                              (296 )               (129 )            (24 )             (8 )         (457 )
Other income and (expenses)          51                    1                1               (7 )           46
. . .