Rate And Regulatory Matters	9 Months Ended
Sep. 30, 2018
Public Utilities, General Disclosures [Abstract]
RATE AND REGULATORY MATTERS	RATE AND REGULATORY MATTERS Below is a summary of updates to significant regulatory proceedings and related lawsuits. See also Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K. We are unable to predict the ultimate outcome of these matters, the timing of the final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity. Missouri Missouri Senate Bill 564 On June 1, 2018, Missouri Senate Bill 564 was enacted. The section of the law applicable to the TCJA was effective immediately; the remaining sections, including the ability to elect PISA, became effective August 28, 2018. The law resulted in certain changes to the regulation of Ameren Missouri’s electric service business. These changes include the reduction of customer rates to pass through the effect of the reduction in the federal statutory corporate income tax rate enacted under the TCJA and, at each electric utility’s election, the use of PISA. The law required the MoPSC to authorize a reduction in Ameren Missouri’s rates to pass through the effect of the TCJA within 90 days of the law’s effective date. In July 2018, the MoPSC authorized Ameren Missouri to reduce its annual revenue requirement by $167 million and reflect that reduction in rates beginning August 1, 2018. The reduction included $74 million for the amortization of excess accumulated deferred income taxes. In addition, Ameren Missouri recorded a reduction to revenue and a corresponding regulatory liability of $60 million for the excess amounts collected in rates related to the TCJA from January 1, 2018, through July 31, 2018. The regulatory liability will be reflected in customer rates over a period of time to be determined by the MoPSC in the next regulatory rate review. Ameren Missouri filed a notification with the MoPSC on September 1, 2018, to elect PISA. Under PISA, Ameren Missouri is permitted to defer and recover 85% of the depreciation expense and a weighted-average cost of capital return on rate base on certain property, plant, and equipment placed in-service after September 1, 2018, and not included in base rates. The rate base on which the return is calculated incorporates qualifying capital expenditures since the PISA election date as well as changes in total accumulated depreciation excluding retirements and plant-related deferred income taxes. The debt return on rate base is recognized in earnings as a reduction of “Interest Charges” until PISA deferrals are reflected in customer rates, while the equity return is recognized in earnings as “Operating Revenues – Electric” when billed to customers. Accumulated PISA deferrals earn carrying costs at the weighted-average cost of capital, and all approved PISA deferrals will be added to rate base prospectively and recovered over a period of 20 years following a regulatory rate review. Costs not included in the PISA deferral, including the remaining 15% of the depreciation expense and return on rate base, remain subject to regulatory lag. Qualifying PISA capital expenditures exclude amounts related to new coal-fired, nuclear, and natural gas generating units and service to new customer premises. Amounts deferred under PISA were immaterial as of September 30, 2018. As a result of Ameren Missouri’s PISA election, additional provisions of Missouri Senate Bill 564 apply, including limiting customer rate increases to a 2.85% compound annual growth rate in the average overall customer rate per kilowatthour, based on the electric rates that became effective in April 2017, less half of the 2018 savings from the TCJA that was passed on to customers. Additionally, Ameren Missouri’s electric base rates, as determined in the July 2018 MoPSC rate order, are frozen until April 1, 2020. Recoveries under the MEEIA, the FAC, and the RESRAM riders have not been frozen; however, except for costs recoverable under the MEEIA rider, Ameren Missouri will be unable to recover any amounts above the 2.85% cap from customers. If rate changes from the FAC or the RESRAM riders would cause rates to temporarily exceed the 2.85% cap, the overage will be deferred for future recovery in the next regulatory rate review; however, rates established in such regulatory rate review will be subject to the rate cap. Any deferred overages approved for recovery will be recovered in a manner consistent with costs recovered under PISA. Both the rate cap and PISA election will be effective through December 2023, unless Ameren Missouri requests and receives MoPSC approval of an extension through December 2028. Ameren Missouri’s PISA election supports Ameren Missouri’s ability to invest approximately $1 billion of incremental capital over the 2019 to 2023 period to strengthen and modernize Missouri’s electric grid. Wind Generation Facilities and RESRAM In the second quarter of 2018, Ameren Missouri entered into an agreement with a subsidiary of Terra-Gen, LLC to acquire, after construction, a 400-megawatt wind generation facility, which is expected to be located in northeastern Missouri. In May 2018, Ameren Missouri filed for a certificate of convenience and necessity with the MoPSC for the 400-megawatt facility. The MoPSC issued an order approving a unanimous stipulation and agreement regarding that requested certificate in October 2018. Also in October 2018, Ameren Missouri entered into an agreement with a subsidiary of EDF Renewables, Inc. to acquire, after construction, a wind generation facility of up to 157 megawatts, and filed for a certificate of convenience and necessity with the MoPSC. The MoPSC is expected to issue an order regarding that certificate by May 2019. The up to 157-megawatt facility is expected to be located in northwestern Missouri. Both facilities are expected to be completed in 2020 and would help Ameren Missouri comply with the state renewable energy standard. Each acquisition is subject to certain conditions, including the issuance of a certificate of convenience and necessity by the MoPSC, obtaining a MISO transmission interconnection agreement, approval by the FERC, and other customary contract terms and conditions. As a part of its May 2018 filing, Ameren Missouri requested the MoPSC to authorize a proposed RESRAM that would allow Ameren Missouri to adjust customer rates on an annual basis without a traditional regulatory rate review. The October 2018 MoPSC order included approval of the RESRAM, without addressing recovery through the RESRAM of the 15% of capital investment not recovered under PISA, which was an objection raised by the MoOPC. Ameren Missouri anticipates a MoPSC decision resolving this remaining issue and approving the RESRAM tariff by December 2018. The RESRAM is designed to mitigate the impacts of regulatory lag for the cost of compliance with renewable energy requirements, including recovery of investments in wind generation and other renewables, by providing more timely recovery of costs and a return on investments not already provided for in customer rates or any other recovery mechanism. RESRAM regulatory assets will earn carrying costs at short-term interest rates. Renewable Choice Program In June 2018, the MoPSC approved Ameren Missouri’s Renewable Choice Program, which allows large commercial and industrial customers and municipalities to elect to receive up to 100 percent of their energy from renewable resources. The tariff-based program is designed to recover the costs of the election, net of changes in the market price of such energy. Based on customer contracts, the program enables Ameren Missouri to supply up to 400 megawatts of renewable wind energy generation, up to 200 megawatts of which it could own. As applicable, the addition of generation by Ameren Missouri would be subject to the issuance of a certificate of convenience and necessity by the MoPSC, obtaining transmission interconnection agreements with MISO or other RTOs, and approval by the FERC. This generation would be incremental to the expected renewable generation included in the 2017 IRP. Without extension, the option to elect into the program will terminate in the third quarter of 2023. MEEIA In June 2018, Ameren Missouri filed a proposed customer energy-efficiency plan with the MoPSC under the MEEIA. In October 2018, Ameren Missouri, the MoPSC staff, the MoOPC, and certain other intervenors filed a stipulation and agreement with the MoPSC with respect to that proposed plan. The proposed plan includes a three-year plan for a portfolio of customer energy-efficiency programs and a six-year plan for low-income energy-efficiency programs, along with a cost recovery mechanism. If the proposal is approved, Ameren Missouri intends to invest $226 million over the life of the plan, including $65 million per program year for the three-year period beginning March 2019. The proposed plan includes the continued use of the MEEIA rider, which allows Ameren Missouri to collect from or refund to customers any difference in actual MEEIA program costs and related lost revenues and the amounts collected from customers. In addition, similar to the MEEIA 2016 plan ending in February 2019, the proposed plan includes a performance incentive that would provide Ameren Missouri an opportunity to earn additional revenues by achieving certain customer energy-efficiency goals, including $30 million if 100% of the goals are achieved during the three-year period beginning March 2019. Additional revenues may be earned if Ameren Missouri exceeds 100% of its energy savings goals. A decision by the MoPSC in this proceeding is anticipated in November 2018. The MEEIA 2016 program provided Ameren Missouri with a performance incentive to earn additional revenues by achieving certain customer energy-efficiency goals, including $27 million if 100% of the goals were achieved during the three-year period beginning March 2016, with the potential to earn more if Ameren Missouri’s energy savings exceeded those goals. In September 2017, Ameren Missouri received an order from the MoPSC approving Ameren Missouri’s energy savings results for the first year of the MEEIA 2016 programs. As a result of this order and in accordance with revenue recognition guidance, Ameren Missouri recognized $5 million of revenues in the first quarter of 2018 relating to the MEEIA 2016 performance incentive. In October 2018, Ameren Missouri received an order from the MoPSC approving Ameren Missouri’s energy savings results for the second year of the MEEIA 2016 programs. As a result of this order, Ameren Missouri will recognize $6 million of additional revenues in the fourth quarter of 2018 relating to the MEEIA 2016 performance incentive. In July 2018, the Missouri Supreme Court overturned a 2016 decision by the Missouri Court of Appeals, Western District, which had upheld a 2015 MoPSC order regarding the determination of a certain input used to calculate the MEEIA 2013 performance incentive, and remanded the matter to the MoPSC. Upon issuance of a MoPSC order, Ameren Missouri expects to recognize an additional $9 million MEEIA 2013 performance incentive. Illinois Electric Distribution Service Rates In April 2018, Ameren Illinois filed its annual electric distribution service formula rate update to establish the revenue requirement to be used for 2019 rates with the ICC. 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. This order reflected an increase to the annual formula rate based on 2017 actual costs and expected net plant additions for 2018, and an increase to include the 2017 revenue requirement reconciliation adjustment. It also included a decrease for the conclusion of the 2016 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2018, consistent with the ICC’s December 2017 annual update filing order. As of September 30, 2018, Ameren Illinois had recorded a regulatory liability of $25 million to reflect the difference between Ameren Illinois’ estimate of its 2018 revenue requirement and the revenue requirement reflected in customer rates, including interest. Electric Customer Energy-Efficiency Investments In June 2018, Ameren Illinois filed its annual electric customer energy-efficiency formula rate update to establish the revenue requirement to be used for 2019 rates with the ICC. In November 2018, the ICC issued an order that approved 2019 rates of $35 million for electric customer energy-efficiency investments, which represents an increase of $20 million from 2018 rates. Income Tax Regulatory Mechanisms In February 2018, the ICC granted Ameren Illinois’ request, filed in January 2018, to establish a rider to reduce Ameren Illinois’ electric distribution customer rates for the effect of the reduction in the federal statutory corporate income tax rate enacted under the TCJA and the return of excess deferred taxes, net of the increase in state income taxes enacted in July 2017. Ameren Illinois' electric distribution customer rates were reduced as a result of the rider beginning in the first quarter of 2018. The estimated reduction of $50 million per year will continue through 2019, as base rates will be adjusted to reflect the current income tax rates starting in 2020. In April 2018, the ICC approved a rider for the difference between revenues billed under natural gas rates established pursuant to Ameren Illinois’ most recent natural gas rate order and the revenues that would have been billed had the state and federal tax rate changes discussed above been in effect. The rider required Ameren Illinois to record this difference as a regulatory liability beginning January 25, 2018. Ameren Illinois’ natural gas customer rates were reduced as a result of the rider beginning in May 2018, with an estimated reduction of up to $17 million to be reflected substantially over a one-year period. 2018 Natural Gas Delivery Service Regulatory Rate Review In January 2018, Ameren Illinois filed a request with the ICC seeking approval to increase its annual rates for natural gas delivery service. In November 2018, the ICC issued an order approving a stipulation and agreement that will result 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. The new rates will be effective starting in November 2018. This increase reflects the reduction in the federal corporate income tax rate as a result of 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. As a result of this order, rate base under the QIP rider has been reset to zero. Ameren Illinois used a 2019 future test year in this proceeding. ATXI’s Illinois Rivers Project In August 2017, the Illinois Circuit Court for Edgar County dismissed several of ATXI’s condemnation cases related to one line segment in the Illinois Rivers project. These cases had been filed to obtain easements and rights of way necessary to complete the line segment. The court found that required notice was not given to the relevant landowners during the underlying ICC proceeding. In November 2017, ATXI appealed this decision to the Illinois Supreme Court. In October 2018, the Illinois Supreme Court reversed the Illinois Circuit Court for Edgar County’s decision and remanded the case for further proceedings. Absent the landowners pursuing rehearing, or a voluntary settlement, ATXI intends to file a motion to reinstate the condemnation cases in the Illinois Circuit Court for Edgar County in the fourth quarter of 2018. ATXI plans to complete the project by the end of 2019; however, delays associated with the condemnation proceedings or a rehearing arising from the Illinois Supreme Court’s ruling could delay the completion date. The estimated line segment capital expenditure investment is approximately $81 million, of which $38 million was invested as of September 30, 2018. The other eight line segments of the Illinois Rivers project are not affected by these proceedings. Federal FERC Complaint Cases In November 2013, a customer group filed a complaint case with the FERC seeking a reduction in the allowed base return on common equity for FERC-regulated transmission rate base under the MISO tariff from 12.38% to 9.15%. In 2016, the FERC issued a final order in the November 2013 complaint case, which lowered the allowed base return on common equity to 10.32%, or a 10.82% total allowed return on common equity with the inclusion of a 50 basis point incentive adder for participation in an RTO, effective since September 2016. The 10.82% allowed return on common equity may be replaced prospectively after the FERC issues a final order in the February 2015 complaint case, discussed below. Since the maximum FERC-allowed refund period for the November 2013 complaint case ended in February 2015, another customer complaint case was filed in February 2015. MISO transmission owners subsequently filed a motion to dismiss the February 2015 complaint, as discussed below. The February 2015 complaint case seeks a further reduction in the allowed base return on common equity for FERC-regulated transmission rate base under the MISO tariff. In June 2016, an administrative law judge issued an initial decision in the February 2015 complaint case. If approved by the FERC, it would lower the allowed base return on common equity for the 15-month period of February 2015 to May 2016 to 9.70%, or a 10.20% total allowed return on equity with the inclusion of a 50 basis point incentive adder for participation in an RTO. It would also require customer refunds, with interest, for that 15-month period. A final FERC order would also establish the allowed return on common equity that will apply prospectively from the effective date of such order, replacing the current 10.82% total return on common equity. In the second quarter of 2017, the United States Court of Appeals for the District of Columbia Circuit vacated and remanded to the FERC an order in an unrelated case in which the FERC established the allowed base return on common equity methodology used in the two MISO complaint cases described above. In October 2018, the FERC issued an order addressing the remanded issues, which proposed a new methodology for determining the base return on equity and required further briefs from the participants. A final order is not expected until 2019. While this order provides insight on how the FERC may determine the return on equity in the MISO complaint cases, Ameren is unable to predict the impact of the outcome on the MISO FERC 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 November 2013 complaint case, is uncertain. In September 2017, MISO transmission owners, including Ameren Missouri, Ameren Illinois, and ATXI, filed a motion to dismiss the February 2015 complaint case with the FERC. The MISO transmission owners maintain that the February 2015 complaint was predicated on the now superseded 12.38% allowed base return on common equity and is therefore inapplicable given the current 10.32% allowed base return on common equity. The MISO transmission owners further maintain that the current 10.32% allowed base return on common equity has not been proven to be unjust and unreasonable based on information provided, including the base return on common equity methodology ranges set forth in the February 2015 complaint case and in the initial decision issued by an administrative law judge in June 2016. Additionally, the MISO transmission owners maintain that the February 2015 complaint should be dismissed because the approach utilized in the case to assert that a return on common equity was unjust and unreasonable was insufficient. That same approach was rejected by the United States Court of Appeals for the District of Columbia Circuit, as discussed above. The FERC is under no deadline to issue an order on this motion. As of September 30, 2018, Ameren and Ameren Illinois had recorded current regulatory liabilities of $43 million and $25 million, respectively, to reflect the expected refunds, including interest, associated with the reduced allowed returns on common equity in the initial decision in the February 2015 complaint case. Ameren Missouri does not expect that a reduction in the FERC-allowed base return on common equity would be material to its results of operations, financial position, or liquidity. FERC Federal Income Tax Proceeding and Formula Rate Change In March 2018, the FERC granted a request filed in February 2018 by MISO transmission owners with forward-looking rate formulas, including Ameren Illinois and ATXI, to allow revisions to their 2018 electric transmission rates to reflect the effect of the reduction in federal income taxes enacted under the TCJA. Ameren Illinois and ATXI’s 2018 electric transmission rates have been reduced by $27 million and $23 million, respectively. In May 2018, the FERC accepted Ameren Illinois and ATXI tariff filings to change the formula rate calculation. The change allows for the recovery or refund of both excess deferred income taxes resulting from tax law or rate changes and effect of permanent income tax differences and will be reflected in Ameren Illinois and ATXI’s electric transmission rates starting in January 2019.

RATE AND REGULATORY MATTERS

Below is a summary of updates to significant regulatory proceedings and related lawsuits. See also Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K. We are unable to predict the ultimate outcome of these matters, the timing of the final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity.

Missouri

Missouri Senate Bill 564

On June 1, 2018, Missouri Senate Bill 564 was enacted. The section of the law applicable to the TCJA was effective immediately; the remaining sections, including the ability to elect PISA, became effective August 28, 2018. The law resulted in certain changes to the regulation of Ameren Missouri’s electric service business. These changes include the reduction of customer rates to pass through the effect of the reduction in the federal statutory corporate income tax rate enacted under the TCJA and, at each electric utility’s election, the use of PISA. The law required the MoPSC to authorize a reduction in Ameren Missouri’s rates to pass through the effect of the TCJA within 90 days of the law’s effective date. In July 2018, the MoPSC authorized Ameren Missouri to reduce its annual revenue requirement by $167 million and reflect that reduction in rates beginning August 1, 2018. The reduction included $74 million for the amortization of excess accumulated deferred income taxes. In addition, Ameren Missouri recorded a reduction to revenue and a corresponding regulatory liability of $60 million for the excess amounts collected in rates related to the TCJA from January 1, 2018, through July 31, 2018. The regulatory liability will be reflected in customer rates over a period of time to be determined by the MoPSC in the next regulatory rate review.

Ameren Missouri filed a notification with the MoPSC on September 1, 2018, to elect PISA. Under PISA, Ameren Missouri is permitted to defer and recover 85% of the depreciation expense and a weighted-average cost of capital return on rate base on certain property, plant, and equipment placed in-service after September 1, 2018, and not included in base rates. The rate base on which the return is calculated incorporates qualifying capital expenditures since the PISA election date as well as changes in total accumulated depreciation excluding retirements and plant-related deferred income taxes. The debt return on rate base is recognized in earnings as a reduction of “Interest Charges” until PISA deferrals are reflected in customer rates, while the equity return is recognized in earnings as “Operating Revenues – Electric” when billed to customers. Accumulated PISA deferrals earn carrying costs at the weighted-average cost of capital, and all approved PISA deferrals will be added to rate base prospectively and recovered over a period of 20 years following a regulatory rate review. Costs not included in the PISA deferral, including the remaining 15% of the depreciation expense and return on rate base, remain subject to regulatory lag. Qualifying PISA capital expenditures exclude amounts related to new coal-fired, nuclear, and natural gas generating units and service to new customer premises. Amounts deferred under PISA were immaterial as of September 30, 2018.

As a result of Ameren Missouri’s PISA election, additional provisions of Missouri Senate Bill 564 apply, including limiting customer rate increases to a 2.85% compound annual growth rate in the average overall customer rate per kilowatthour, based on the electric rates that became effective in April 2017, less half of the 2018 savings from the TCJA that was passed on to customers. Additionally, Ameren Missouri’s electric base rates, as determined in the July 2018 MoPSC rate order, are frozen until April 1, 2020. Recoveries under the MEEIA, the FAC, and the RESRAM riders have not been frozen; however, except for costs recoverable under the MEEIA rider, Ameren Missouri will be unable to recover any amounts above the 2.85% cap from customers. If rate changes from the FAC or the RESRAM riders would cause rates to temporarily exceed the 2.85% cap, the overage will be deferred for future recovery in the next regulatory rate review; however, rates established in such regulatory rate review will be subject to the rate cap. Any deferred overages approved for recovery will be recovered in a manner consistent with costs recovered under PISA. Both the rate cap and PISA election will be effective through December 2023, unless Ameren Missouri requests and receives MoPSC approval of an extension through December 2028. Ameren Missouri’s PISA election supports Ameren Missouri’s ability to invest approximately $1 billion of incremental capital over the 2019 to 2023 period to strengthen and modernize Missouri’s electric grid.

Wind Generation Facilities and RESRAM

In the second quarter of 2018, Ameren Missouri entered into an agreement with a subsidiary of Terra-Gen, LLC to acquire, after construction, a 400-megawatt wind generation facility, which is expected to be located in northeastern Missouri. In May 2018, Ameren Missouri filed for a certificate of convenience and necessity with the MoPSC for the 400-megawatt facility. The MoPSC issued an order approving a unanimous stipulation and agreement regarding that requested certificate in October 2018. Also in October 2018, Ameren Missouri entered into an agreement with a subsidiary of EDF Renewables, Inc. to acquire, after construction, a wind generation facility of up to 157 megawatts, and filed for a certificate of convenience and necessity with the MoPSC. The MoPSC is expected to issue an order regarding that certificate by May 2019. The up to 157-megawatt facility is expected to be located in northwestern Missouri. Both facilities are expected to be completed in 2020 and would help Ameren Missouri comply with the state renewable energy standard. Each acquisition is subject to certain conditions, including the issuance of a certificate of convenience and necessity by the MoPSC, obtaining a MISO transmission interconnection agreement, approval by the FERC, and other customary contract terms and conditions.

As a part of its May 2018 filing, Ameren Missouri requested the MoPSC to authorize a proposed RESRAM that would allow Ameren Missouri to adjust customer rates on an annual basis without a traditional regulatory rate review. The October 2018 MoPSC order included approval of the RESRAM, without addressing recovery through the RESRAM of the 15% of capital investment not recovered under PISA, which was an objection raised by the MoOPC. Ameren Missouri anticipates a MoPSC decision resolving this remaining issue and approving the RESRAM tariff by December 2018. The RESRAM is designed to mitigate the impacts of regulatory lag for the cost of compliance with renewable energy requirements, including recovery of investments in wind generation and other renewables, by providing more timely recovery of costs and a return on investments not already provided for in customer rates or any other recovery mechanism. RESRAM regulatory assets will earn carrying costs at short-term interest rates.

Renewable Choice Program

In June 2018, the MoPSC approved Ameren Missouri’s Renewable Choice Program, which allows large commercial and industrial customers and municipalities to elect to receive up to 100 percent of their energy from renewable resources. The tariff-based program is designed to recover the costs of the election, net of changes in the market price of such energy. Based on customer contracts, the program enables Ameren Missouri to supply up to 400 megawatts of renewable wind energy generation, up to 200 megawatts of which it could own. As applicable, the addition of generation by Ameren Missouri would be subject to the issuance of a certificate of convenience and necessity by the MoPSC, obtaining transmission interconnection agreements with MISO or other RTOs, and approval by the FERC. This generation would be incremental to the expected renewable generation included in the 2017 IRP. Without extension, the option to elect into the program will terminate in the third quarter of 2023.

MEEIA

In June 2018, Ameren Missouri filed a proposed customer energy-efficiency plan with the MoPSC under the MEEIA. In October 2018, Ameren Missouri, the MoPSC staff, the MoOPC, and certain other intervenors filed a stipulation and agreement with the MoPSC with respect to that proposed plan. The proposed plan includes a three-year plan for a portfolio of customer energy-efficiency programs and a six-year plan for low-income energy-efficiency programs, along with a cost recovery mechanism. If the proposal is approved, Ameren Missouri intends to invest $226 million over the life of the plan, including $65 million per program year for the three-year period beginning March 2019. The proposed plan includes the continued use of the MEEIA rider, which allows Ameren Missouri to collect from or refund to customers any difference in actual MEEIA program costs and related lost revenues and the amounts collected from customers. In addition, similar to the MEEIA 2016 plan ending in February 2019, the proposed plan includes a performance incentive that would provide Ameren Missouri an opportunity to earn additional revenues by achieving certain customer energy-efficiency goals, including $30 million if 100% of the goals are achieved during the three-year period beginning March 2019. Additional revenues may be earned if Ameren Missouri exceeds 100% of its energy savings goals. A decision by the MoPSC in this proceeding is anticipated in November 2018.

The MEEIA 2016 program provided Ameren Missouri with a performance incentive to earn additional revenues by achieving certain customer energy-efficiency goals, including $27 million if 100% of the goals were achieved during the three-year period beginning March 2016, with the potential to earn more if Ameren Missouri’s energy savings exceeded those goals. In September 2017, Ameren Missouri received an order from the MoPSC approving Ameren Missouri’s energy savings results for the first year of the MEEIA 2016 programs. As a result of this order and in accordance with revenue recognition guidance, Ameren Missouri recognized $5 million of revenues in the first quarter of 2018 relating to the MEEIA 2016 performance incentive. In October 2018, Ameren Missouri received an order from the MoPSC approving Ameren Missouri’s energy savings results for the second year of the MEEIA 2016 programs. As a result of this order, Ameren Missouri will recognize $6 million of additional revenues in the fourth quarter of 2018 relating to the MEEIA 2016 performance incentive.

In July 2018, the Missouri Supreme Court overturned a 2016 decision by the Missouri Court of Appeals, Western District, which had upheld a 2015 MoPSC order regarding the determination of a certain input used to calculate the MEEIA 2013 performance incentive, and remanded the matter to the MoPSC. Upon issuance of a MoPSC order, Ameren Missouri expects to recognize an additional $9 million MEEIA 2013 performance incentive.

Illinois

Electric Distribution Service Rates

In April 2018, Ameren Illinois filed its annual electric distribution service formula rate update to establish the revenue requirement to be used for 2019 rates with the ICC. 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. This order reflected an increase to the annual formula rate based on 2017 actual costs and expected net plant additions for 2018, and an increase to include the 2017 revenue requirement reconciliation adjustment. It also included a decrease for the conclusion of the 2016 revenue requirement reconciliation adjustment, which will be fully collected from customers in 2018, consistent with the ICC’s December 2017 annual update filing order. As of September 30, 2018, Ameren Illinois had recorded a regulatory liability of $25 million to reflect the difference between Ameren Illinois’ estimate of its 2018 revenue requirement and the revenue requirement reflected in customer rates, including interest.

Electric Customer Energy-Efficiency Investments

In June 2018, Ameren Illinois filed its annual electric customer energy-efficiency formula rate update to establish the revenue requirement to be used for 2019 rates with the ICC. In November 2018, the ICC issued an order that approved 2019 rates of $35 million for electric customer energy-efficiency investments, which represents an increase of $20 million from 2018 rates.

Income Tax Regulatory Mechanisms

In February 2018, the ICC granted Ameren Illinois’ request, filed in January 2018, to establish a rider to reduce Ameren Illinois’ electric distribution customer rates for the effect of the reduction in the federal statutory corporate income tax rate enacted under the TCJA and the return of excess deferred taxes, net of the increase in state income taxes enacted in July 2017. Ameren Illinois' electric distribution customer rates were reduced as a result of the rider beginning in the first quarter of 2018. The estimated reduction of $50 million per year will continue through 2019, as base rates will be adjusted to reflect the current income tax rates starting in 2020.

In April 2018, the ICC approved a rider for the difference between revenues billed under natural gas rates established pursuant to Ameren Illinois’ most recent natural gas rate order and the revenues that would have been billed had the state and federal tax rate changes discussed above been in effect. The rider required Ameren Illinois to record this difference as a regulatory liability beginning January 25, 2018. Ameren Illinois’ natural gas customer rates were reduced as a result of the rider beginning in May 2018, with an estimated reduction of up to $17 million to be reflected substantially over a one-year period.

2018 Natural Gas Delivery Service Regulatory Rate Review

In January 2018, Ameren Illinois filed a request with the ICC seeking approval to increase its annual rates for natural gas delivery service. In November 2018, the ICC issued an order approving a stipulation and agreement that will result 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. The new rates will be effective starting in November 2018. This increase reflects the reduction in the federal corporate income tax rate as a result of 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. As a result of this order, rate base under the QIP rider has been reset to zero. Ameren Illinois used a 2019 future test year in this proceeding.

ATXI’s Illinois Rivers Project

In August 2017, the Illinois Circuit Court for Edgar County dismissed several of ATXI’s condemnation cases related to one line segment in the Illinois Rivers project. These cases had been filed to obtain easements and rights of way necessary to complete the line segment. The court found that required notice was not given to the relevant landowners during the underlying ICC proceeding. In November 2017, ATXI appealed this decision to the Illinois Supreme Court. In October 2018, the Illinois Supreme Court reversed the Illinois Circuit Court for Edgar County’s decision and remanded the case for further proceedings. Absent the landowners pursuing rehearing, or a voluntary settlement, ATXI intends to file a motion to reinstate the condemnation cases in the Illinois Circuit Court for Edgar County in the fourth quarter of 2018. ATXI plans to complete the project by the end of 2019; however, delays associated with the condemnation proceedings or a rehearing arising from the Illinois Supreme Court’s ruling could delay the completion date. The estimated line segment capital expenditure investment is approximately $81 million, of which $38 million was invested as of September 30, 2018. The other eight line segments of the Illinois Rivers project are not affected by these proceedings.

Federal

FERC Complaint Cases

In November 2013, a customer group filed a complaint case with the FERC seeking a reduction in the allowed base return on common equity for FERC-regulated transmission rate base under the MISO tariff from 12.38% to 9.15%. In 2016, the FERC issued a final order in the November 2013 complaint case, which lowered the allowed base return on common equity to 10.32%, or a 10.82% total allowed return on common equity with the inclusion of a 50 basis point incentive adder for participation in an RTO, effective since September 2016. The 10.82% allowed return on common equity may be replaced prospectively after the FERC issues a final order in the February 2015 complaint case, discussed below.

Since the maximum FERC-allowed refund period for the November 2013 complaint case ended in February 2015, another customer complaint case was filed in February 2015. MISO transmission owners subsequently filed a motion to dismiss the February 2015 complaint, as discussed below. The February 2015 complaint case seeks a further reduction in the allowed base return on common equity for FERC-regulated transmission rate base under the MISO tariff. In June 2016, an administrative law judge issued an initial decision in the February 2015 complaint case. If approved by the FERC, it would lower the allowed base return on common equity for the 15-month period of February 2015 to May 2016 to 9.70%, or a 10.20% total allowed return on equity with the inclusion of a 50 basis point incentive adder for participation in an RTO. It would also require customer refunds, with interest, for that 15-month period. A final FERC order would also establish the allowed return on common equity that will apply prospectively from the effective date of such order, replacing the current 10.82% total return on common equity. In the second quarter of 2017, the United States Court of Appeals for the District of Columbia Circuit vacated and remanded to the FERC an order in an unrelated case in which the FERC established the allowed base return on common equity methodology used in the two MISO complaint cases described above. In October 2018, the FERC issued an order addressing the remanded issues, which proposed a new methodology for determining the base return on equity and required further briefs from the participants. A final order is not expected until 2019. While this order provides insight on how the FERC may determine the return on equity in the MISO complaint cases, Ameren is unable to predict the impact of the outcome on the MISO FERC 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 November 2013 complaint case, is uncertain.

In September 2017, MISO transmission owners, including Ameren Missouri, Ameren Illinois, and ATXI, filed a motion to dismiss the February 2015 complaint case with the FERC. The MISO transmission owners maintain that the February 2015 complaint was predicated on the now superseded 12.38% allowed base return on common equity and is therefore inapplicable given the current 10.32% allowed base return on common equity. The MISO transmission owners further maintain that the current 10.32% allowed base return on common equity has not been proven to be unjust and unreasonable based on information provided, including the base return on common equity methodology ranges set forth in the February 2015 complaint case and in the initial decision issued by an administrative law judge in June 2016. Additionally, the MISO transmission owners maintain that the February 2015 complaint should be dismissed because the approach utilized in the case to assert that a return on common equity was unjust and unreasonable was insufficient. That same approach was rejected by the United States Court of Appeals for the District of Columbia Circuit, as discussed above. The FERC is under no deadline to issue an order on this motion.

As of September 30, 2018, Ameren and Ameren Illinois had recorded current regulatory liabilities of $43 million and $25 million, respectively, to reflect the expected refunds, including interest, associated with the reduced allowed returns on common equity in the initial decision in the February 2015 complaint case. Ameren Missouri does not expect that a reduction in the FERC-allowed base return on common equity would be material to its results of operations, financial position, or liquidity.

FERC Federal Income Tax Proceeding and Formula Rate Change

In March 2018, the FERC granted a request filed in February 2018 by MISO transmission owners with forward-looking rate formulas, including Ameren Illinois and ATXI, to allow revisions to their 2018 electric transmission rates to reflect the effect of the reduction in federal income taxes enacted under the TCJA. Ameren Illinois and ATXI’s 2018 electric transmission rates have been reduced by $27 million and $23 million, respectively.

In May 2018, the FERC accepted Ameren Illinois and ATXI tariff filings to change the formula rate calculation. The change allows for the recovery or refund of both excess deferred income taxes resulting from tax law or rate changes and effect of permanent income tax differences and will be reflected in Ameren Illinois and ATXI’s electric transmission rates starting in January 2019.