2019 revenue requirements included in rates for Ameren Illinois’ and ATXI’s electric transmission businesses are \$297 million and \$177 million, respectively. These revenue requirements represent an increase in Ameren Illinois' and ATXI’s revenue requirements of \$24 million and \$3 million, respectively, primarily because of the rate base growth. These rates will affect Ameren Illinois’ and ATXI’s cash receipts during 2019, but will not determine their respective electric transmission service operating revenues, which will instead be based on 2019 actual recoverable costs, rate base, and return on common equity as calculated under the FERC formula ratemaking framework.

• The return on common equity for MISO transmission owners, including Ameren Illinois and ATXI, is the subject of a FERC complaint case filed in February 2015 challenging the allowed base return on common equity. Ameren Illinois and ATXI currently use the FERC authorized total allowed return on common equity of 10.82% in customer rates. A final FERC order would establish the allowed return on common equity to be applied to the 15-month period from February 2015 to May 2016 and also establish the return on common equity to be included in customer rates prospectively from the effective date of such order, replacing the current 10.82% total return on common equity. In October 2018, the FERC issued an order addressing the remanded issues in an unrelated case. That order proposed a new methodology for determining the base return on equity and required further briefs from the participants. In November 2018, the FERC issued an order related to the February 2015 complaint case and the September 2016 final order, which required briefs from the participants to be filed in February 2019 regarding a new methodology for determining the base return on common equity and whether and how to apply the new methodology to the two MISO complaint cases. Ameren is unable to predict the ultimate impact of the proposed methodology on these complaint cases at this time. As the FERC is under no deadline to issue a final order, the timing of the issuance of the final order in the February 2015 complaint case, or any potential impact to the amounts refunded as a result of the September 2016 final order, is uncertain. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for information regarding FERC complaint cases. A 50 basis point reduction in the FERC-allowed base return on common equity would reduce Ameren’s and Ameren Illinois’ net income by an estimated \$9 million and \$5 million , respectively, based on each company’s 2019 projected rate base.

• In November 2018, the ICC issued an order in Ameren Illinois’ annual update filing that approved a \$72 million increase in Ameren Illinois’ electric distribution service rates beginning in January 2019. However, Illinois law provides for an annual reconciliation of the electric distribution revenue requirement as is necessary to reflect the actual costs incurred and investment return in a given year with the revenue requirement that was reflected in customer rates for that year. Consequently, Ameren Illinois’ 2019 electric distribution service revenues will be based on its 2019 actual recoverable costs, rate base, and return on common equity as calculated under the Illinois performance-based formula ratemaking framework. The 2019 revenue requirement is expected to be higher than the 2018 revenue requirement because of an expected increase in recoverable costs, expected rate base growth of approximately 8%, and an expected increase in the annual average of the monthly yields of the 30-year United States Treasury bonds. The 2019 revenue requirement reconciliation is expected to result in a regulatory asset that will be collected from customers in 2021. A 50 basis point change in the annual average of the monthly yields of the 30-year United States Treasury bonds would result in an estimated \$8 million change in Ameren’s and Ameren Illinois’ net income, based on Ameren Illinois’ 2019 projected year-end rate base.

• Ameren Illinois is allowed to earn a return on its electric energy-efficiency program investments. Ameren Illinois’ electric energy-efficiency investments are deferred as a regulatory asset and earn a return at its weighted-average cost of capital, with the equity return based on the annual average of the monthly yields of the 30-year United States Treasury bonds plus 580 basis points. The equity portion of Ameren Illinois’ return on electric energy-efficiency investments can be increased or decreased by up to 200 basis points, depending on the achievement of annual energy savings goals. Pursuant to the FEJA, Ameren Illinois plans to invest up to \$100 million per year in electric energy-efficiency programs through 2023 and will earn a return on those investments. The ICC has the ability to reduce electric energy-efficiency savings goals if there are insufficient cost-effective programs available or if the savings goals would require investment levels that exceed amounts allowed by legislation. The electric energy-efficiency program investments and the return on those investments are collected from customers through a rider and are not included in the electric distribution formula ratemaking framework. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for information regarding Ameren Illinois’ energy-efficiency program.

• In November 2018, the ICC issued an order approving a stipulation and agreement that resulted in an annual natural gas rate increase of \$32 million, based on a 9.87% return on common equity, a capital structure composed of 50% common equity, and a rate base of \$1.6 billion. This increase reflects the reduction in the federal statutory corporate income tax rate enacted under the TCJA, as well as the increase in the Illinois corporate income tax rate that became effective in July 2017, which collectively decreased annual rates by approximately \$17 million. The new customer rates were effective in November 2018. As a result of this order, the rate base under the QIP rider was reset to zero. Ameren Illinois used a 2019 future test year in this proceeding.

• Ameren Missouri’s next scheduled refueling and maintenance outage at its Callaway energy center is scheduled for the spring of 2019. During the 2017 refueling, Ameren Missouri incurred maintenance expenses of \$35 million. During a scheduled refueling, which occurs every 18 months, maintenance expenses increase relative to non-outage years. Additionally, depending on the availability of its other generation sources and the market prices for power, Ameren Missouri’s purchased power costs may increase and the amount of excess