2018 Annual Attachment O Stakeholder Meeting Ameren Missouri July 10, 2018

Agenda Primary purpose is to review AMMO Pricing Zone Historical 2017 Transmission Rate Calculations which became effective June 1, 2018 Protocol Timeline Attachment O Template Changes ROE Complaint Cases Comparison to Previous Revenue Requirement 2018 AMMO Pricing Zone NITS Charge

Protocol timeline Date Action (Historical) June 1 Posting of annual update Information exchange period begins. Review period begins. September 1 Deadline for annual meeting November 1 Deadline for joint meeting on regional cost-shared projects December 1 Deadline for Interested Parties to submit information requests January 10 Deadline for Transmission Owners to respond to information requests January 31 Deadline for Interested Parties to submit Informal Challenges February 28 Deadline for Transmission Owners to respond to Informal Challenges Any rate changes agreed to by the Transmission Owner will be included in the Information Filing and will be reflected in the Annual Update for the following Rate Year. March 15 Transmission Owners submit informational filing to the Commission. March 31 Deadline for Interested Parties to file Formal Challenge at the Commission

Ameren Missouri Attachment O tariff changes Docket ER17-2323 FERC Order on May 31, 2018 Effective June 1, 2018 for Ameren Missouri Approved company-specific Attachment O for Ameren Missouri Approved additional lines in the Income Tax Section (Page 3, Lines 24a/24b and 26a/26b) Modification to return to (or recover from) customers excess (or deficient) accumulated deferred income taxes (ADIT) resulting from tax law or rate changes An adjustment to recognize the effects of permanent differences between tax accounting and financial reporting, such as those associated with the equity component of Allowance for Funds Used During Construction (AFUDC) Equity Revised 2017 Annual Update including these changes was posted on Ameren’s OASIS and is included in the rates effective June 1, 2018 These tariff changes resulted in an increase of $1,063,389 to the net Attachment O revenue requirement and an increase of $145,406 to the Attachment GG revenue requirement

Roe complaint MISO ROE Complaints RTO Adder (ER15-358) 1st Complaint (EL14-12) Covers November 12, 2013 through February 11, 2015 FERC order received September 28, 2016; set the Base ROE at 10.32% Applicable going forward until 2nd complaint order 2nd Complaint (EL15-45) Covers February 12, 2015 through May 11, 2016 Initial decision issued June 30, 2016 with a recommended Base ROE at 9.70% Additional refunds may be required upon receipt of Final Order RTO Adder (ER15-358) FERC approved a 50 basis point adder for participation in an RTO Effective January 6, 2015, applicable to complaint case refunds after that date and going forward (i.e., total ROE is now 10.82%)

Current effective ROE is 10.82% Roe complaint Current effective ROE is 10.82% Effective revenue requirement will be adjusted as needed for new ROE upon receipt of Order in 2nd Complaint Case Refunds already provided for EL14-12 Two phase process Phase 1 related to ROE impact on projected rates for forward looking TOs and annual updates for historical TOs. These were settled in February 2017. Point-to-point refunds made by Ameren Missouri are treated as an adjustment in the 2016 Annual Update Phase 2 related to the ROE impact on true-ups calculations for forward looking TOs. These were settled in June 2017. No Phase 2 schedule 9 refunds for Ameren Missouri since they are historical Refunds for Schedules 7, 8, 26, 37, 38, 26A were completed by MISO Refunds for Schedule 9 were completed by Ameren Small point-to-point amounts related to Phase 2 of ROE are included in the 2017 True-Up. Schedule 9 Refund amounts and supporting documents are posted on OASIS

June 2017 vs June 2018 Calculation Ameren Missouri Revenue Requirement June 2017 vs June 2018 Calculation

Ameren Missouri June 2018 Calculation Rate Base Page.Line Jun-17 Jun-18 Change Percent 2.6 Total Gross Plant 1,176,985,925 1,229,731,470 52,745,544 4% 2.12 Total Accum Depreciation 337,277,231 358,956,337 21,679,107 6% 2.18 TOTAL NET PLANT 839,708,694 870,775,132 31,066,438 ADJUSTMENTS TO RATE BASE 2.20 Account No. 282 (241,157,155) (257,137,887) (15,980,731) 7% 2.21 Account No. 283 (6,231,888) (6,584,410) (352,522) 2.22 Account No. 190 6,048,866 12,695,516 6,646,650 110% 2.25 Land Held for Future Use 4,741,655 6,181,437 1,439,782 30% 2.26 CWC 4,446,739 4,367,355 (79,385) -2% 2.27 Materials & Supplies 4,105,744 3,958,847 (146,898) -4% 2.28 Prepayments 1,210,298 1,183,365 (26,934) TOTAL ADJUSTMENTS (226,835,740) (235,335,777) (8,500,038) 2.30 TOTAL RATE BASE 612,872,955 635,439,355 22,566,400

Ameren Missouri June 2018 Calculation Expenses Page.Line Jun-17 Jun-18 Change Percent O&M 3.1 Transmission 77,077,746 92,937,081 15,859,335 21% 3.1a Less LSE Expenses 6,676,917 6,738,357 61,440 1% 3.2 Less Account 565 43,363,135 59,557,269 16,194,134 37% 3.3 A&G 7,899,056 7,706,698 (192,358) -2% 3.4 Less FERC Annual Fees - N/A 3.5 Less EPRI, ect. 634,804 694,050 59,246 9% 3.5a Plus Trans. Reg. Comm. Exp 32,280 107,355 75,075 233% 3.7 Transmission Lease Payments 1,239,690 1,177,380 (62,310) -5% 3.8 TOTAL O&M 35,573,915 34,938,838 (635,078) 3.12 TOTAL DEPRECIATION 26,760,281 30,278,318 3,518,037 13% TAXES 3.13 Payroll 607,758 649,658 41,900 7% 3.16 Property 10,222,922 10,406,484 183,562 2% 3.18 Other 9,987 41,416 31,429 315% 3.27 Income Taxes* 20,442,429 12,589,728 (7,852,701) -38% TOTAL TAXES 31,283,096 23,687,286 (7,595,811) -24% TOTAL EXPENSES 93,617,292 88,904,441 (4,712,851) *The June 2017 Income Taxes above are at the old Federal Income Tax Rate of 35%. The June 2018 amounts reflect the current Federal Income Tax Rate of 21% as a result of the Tax Cuts and Jobs Act which became effective January 1, 2018. The June 2018 income taxes also include the adjustment related to Docket ER17-2323 (discussed on slide 4).

Ameren Missouri June 2018 Calculation Capital Structure Capital Structure - June 2017 Page.Line $ % Cost Weighted 4.27 Long Term Debt 3,737,276,000 48% 0.0522 0.0249 4.28 Preferred Stock 80,759,500 1% 0.0424 0.0004 4.29 Common Stock 4,009,795,947 51% 0.1082 0.0554 4.3 Total 7,827,831,447 100% 0.0808 Capital Structure - June 2018 3,712,276,000 0.0512 0.0244 4,000,217,417 0.0555 7,793,252,917 0.0803 Change in Return -0.0431%

Ameren Missouri June 2018 Calculation Revenue Requirement Page.Line Jun-17 Jun-18 Change Percent 2.30 TOTAL RATE BASE 612,872,955 635,439,355 22,566,400 4% 4.30 Rate of Return 0.0808 0.0803 (0.0004) -1% 3.28 Return 49,506,223 51,054,978 1,548,755 3% Total Expenses 93,617,292 88,904,441 (4,712,851) -5% 3.29 TOTAL GROSS REV. REQ. 143,123,514 139,959,419 (3,164,095) -2% 3.30 Less ATT. GG Adjustment 15,562,140 14,604,193 (957,947) -6% 3.30a Less ATT. MM Adjustment - N/A 3.31 GROSS REV. REQ. UNDER ATT. O 127,561,375 125,355,226 (2,206,149)

Ameren Missouri June 2018 Calculation Net Revenue Requirement Page.Line Jun-17 Jun-18 Change Percent 1.1 Gross Revenue Requirement 127,561,375 125,355,226 -2,206,149 -2% 1.6 Total Revenue Credits 6,377,122 6,176,051 -201,071 -3% 1.6c Total Prior Period Adjustment (with interest) 605,636 -5,871 -611,507 -101% 1.7 NET REVENUE REQUIREMENT 121,789,889 119,173,304 -2,616,585 The Prior Period Adjustments for June 2017 relate to the point-to-point portion of the ROE refund required per the Order in Docket No. EL14-12 (Phase 1) The Prior Period Adjustments for June 2018 relate to the point-to-point portion of the ROE refund required per the Order in Docket No. EL14-12 (Phase 2)

Ameren Missouri June 2018 Calculation AMMO Schedule 9 Rate Calculation Page.Line Jun-17 Jun-18 Change Percent 1.7 Net Revenue Requirement 121,789,889 119,173,304 -2,616,585 -2% 1.15 Ameren Missouri Divisor 6,317,790 6,206,891 (110,899) Annual Cost ($/kW/Yr) 19.277 19.200 (0.077) 0% Network & P-to-P Rate ($/kW/Mo) 1.606 1.600 (0.006) The divisor excludes the Southeast Missouri load included in the Entergy Arkansas, Inc. (EAI) pricing zone.

Ameren Missouri June 2018 Calculation Attachment GG Calculation - Page 1 (1) (2) (3) (4) Attachment O Line Page, Line, Col. Transmission Allocator No. 1 Gross Transmission Plant - Total Attach O, p 2, line 2 col 5 (Note A) 1,201,003,944 2 Net Transmission Plant - Total Attach O, p 2, line 14 and 23b col 5 (Note B) 853,685,594 O&M EXPENSE 3 Total O&M Allocated to Transmission Attach O, p 3, line 8 col 5 34,938,838 4 Annual Allocation Factor for O&M (line 3 divided by line 1 col 3) 2.91% GENERAL AND COMMON (G&C) DEPRECIATION EXPENSE 5 Total G&C Depreciation Expense Attach O, p 3, lines 10 & 11, col 5 (Note H) 1,405,048 6 Annual Allocation Factor for G&C Depreciation Expense (line 5 divided by line 1 col 3) 0.12% TAXES OTHER THAN INCOME TAXES 7 Total Other Taxes Attach O, p 3, line 20 col 5 11,097,557 8 Annual Allocation Factor for Other Taxes (line 7 divided by line 1 col 3) 0.92% 9 Annual Allocation Factor for Expense Sum of line 4, 6, and 8 3.95% INCOME TAXES 10 Total Income Taxes Attach O, p 3, line 27 col 5 12,589,728 11 Annual Allocation Factor for Income Taxes (line 10 divided by line 2 col 3) 1.47% RETURN 12 Return on Rate Base Attach O, p 3, line 28 col 5 51,054,978 13 Annual Allocation Factor for Return on Rate Base (line 12 divided by line 2 col 3) 5.98% 14 Annual Allocation Factor for Return Sum of line 11 and 13 7.46%

Ameren Missouri June 2018 Calculation Attachment GG Calculation - Page 2 (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) Line No.   Project Name MTEP Project Number Project Gross Plant Annual Allocation Factor for Expense Annual Expense Charge Project Net Plant Annual Allocation Factor for Return Annual Return Charge Project Depreciation Expense Annual Revenue Requirement True-Up Adjustment Network Upgrade Charge (Note C) (Page 1 line 9) (Col. 3 * Col. 4) (Note D) (Page 1 line 14) (Col. 6 * Col. 7) (Note E) (Sum Col. 5, 8 & 9) (Note F) Sum Col. 10 & 11 (Note G) 1a Big River-Rockwood 138 kV 152 $15,650,433 3.95% $618,215 $13,617,069 7.46% $1,015,192 $332,689 $1,966,096 $ - 1b Reconductor Sioux-Huster-1 and -3 138 kV 1240 $15,553,957 $614,404 $13,011,572 $970,050 $403,455 $1,987,909 1c Gray Summit : 2nd 345/138 kV Transformer 2061 $22,410,811 $885,260 $19,436,641 $1,449,057 $407,469 $2,741,787 1d Lutesville: Northwest Cape 345/161 kV substation and new lines 2306 $58,887,812 $2,326,156 $56,624,642 $4,221,529 $1,360,716 $7,908,401 2 Annual Totals $14,604,193 $0 3 Rev. Req. Adj For Attachment O

Significant transmission projects in 2017 and 2018 Completed in 2017 Project Name Total Cost Intelligrid $16 Million Sioux-Viele $6 Million Page-Mason To Be Completed in 2018 Project Name Total Cost Intelligrid $16 Million Venice-Campbell $9 Million CIP V5 $7 Million Rush Island-Tyson Lutesville-St. Francois $5 Million

Additional information Additional questions can be sent to Ameren at: MISOFormulaRates@ameren.com MISO Web Links Transmission Pricing - Attachments O, GG & MM Information https://www.misoenergy.org/markets-and-operations/ts-pricing Ameren OASIS http://www.oasis.oati.com/AMRN/index.html MTEP 18 https://www.misoenergy.org/planning/transmission-studies-and-reports/#nt=%2Freport-study-analysistype%3AMTEP%2Fmtepdoctype%3AMTEP%20Report%2Fmtepreportyear%3AMTEP18&t=10&p=0&s=&sd= MTEP 17 https://www.misoenergy.org/planning/transmission-studies-and-reports/#nt=%2Freport-study-analysistype%3AMTEP%2Fmtepdoctype%3AMTEP%20Report%2Fmtepreportyear%3AMTEP17&t=10&p=0&s=&sd= Schedule 26 & 26-A Indicative Charges https://www.misoenergy.org/planning/transmission-studies-and-reports/#nt=/report-study-analysistype:MTEP/mtepdoctype:MTEP Study/mtepstudytype:Indicative Rate Reports