2017 Annual Attachment O Stakeholder Meeting Ameren Missouri July 11, 2017

Agenda Primary purpose is to review AMMO Pricing Zone Historical 2016 Transmission Rate Calculations which became effective June 1, 2017 Protocol Timeline ROE Complaint Cases Comparison to Previous Revenue Requirement 2017 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

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 will 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 will flow through the 2017 True-Up. Schedule 9 Refund amounts and supporting documents are posted on OASIS

Ameren Missouri Revenue Requirement June 2016 vs June 2017 Calculation For comparison purposes, both years based on 10.82% ROE per the Order issued in Docket EL14-12

Ameren Missouri June 2017 Calculation Rate Base Page.Line Jun-16 Jun-17 Change Percent 2.6 Total Gross Plant 1,002,549,260 1,176,985,925 174,436,665 17% 2.12 Total Accum Depreciation 317,488,807 337,277,231 19,788,424 6% 2.18 TOTAL NET PLANT 685,060,453 839,708,694 154,648,241 23% ADJUSTMENTS TO RATE BASE 2.20 Account No. 282 (193,381,672) (241,157,155) (47,775,483) 25% 2.21 Account No. 283 (6,947,952) (6,231,888) 716,064 -10% 2.22 Account No. 190 4,830,788 6,048,866 1,218,078 2.25 Land Held for Future Use 3,334,568 4,741,655 1,407,087 42% 2.26 CWC 4,099,708 4,446,739 347,031 8% 2.27 Materials & Supplies 7,423,375 4,105,744 (3,317,631) -45% 2.28 Prepayments 946,165 1,210,298 264,133 28% TOTAL ADJUSTMENTS (179,695,020) (226,835,740) (47,140,720) 26% 2.30 TOTAL RATE BASE 505,365,433 612,872,955 107,507,522 21%

Ameren Missouri June 2017 Calculation Expenses Page.Line Jun-16 Jun-17 Change Percent O&M 3.1 Transmission 67,034,333 77,077,746 10,043,413 15% 3.1a Less LSE Expenses 6,469,633 6,676,917 207,284 3% 3.2 Less Account 565 36,318,361 43,363,135 7,044,774 19% 3.3 A&G 8,060,504 7,899,056 (161,448) -2% 3.4 Less FERC Annual Fees - N/A 3.5 Less EPRI, ect. 651,660 634,804 (16,856) -3% 3.5a Plus Trans. Reg. Comm. Exp 41,882 32,280 (9,602) -23% 3.7 Transmission Lease Payments 1,100,598 1,239,690 139,092 13% 3.8 TOTAL O&M 32,797,663 35,573,915 2,776,252 8% 3.12 TOTAL DEPRECIATION 24,671,586 26,760,281 2,088,695 TAXES 3.13 Payroll 596,060 607,758 11,698 2% 3.16 Property 9,375,098 10,222,922 847,824 9% 3.18 Other 77,189 9,987 (67,202) -87% 3.27 Income Taxes 16,697,187 20,442,429 3,745,242 22% TOTAL TAXES 26,745,534 31,283,096 4,537,562 17% TOTAL EXPENSES 84,214,783 93,617,292 9,402,509 11%

Ameren Missouri June 2017 Calculation Capital Structure Capital Structure - June 2016 Page.Line $ % Cost Weighted 4.27 Long Term Debt 3,847,276,000 49% 0.0527 0.0256 4.28 Preferred Stock 80,759,500 1% 0.0424 0.0004 4.29 Common Stock 4,001,834,831 50% 0.1082 0.0546 4.3 Total 7,929,870,331 100% 0.0806 Capital Structure - June 2017 3,737,276,000 48% 0.0522 0.0249 4,009,795,947 51% 0.0554 7,827,831,447 0.0808 Change in Return 0.0160%

Ameren Missouri June 2017 Calculation Revenue Requirement Page.Line Jun-16 Jun-17 Change Percent 2.30 TOTAL RATE BASE 505,365,433 612,872,955 107,507,522 21% 4.30 Rate of Return 0.0806 0.0808 0.0002 0% 3.28 Return 40,741,013 49,506,223 8,765,211 22% Total Expenses 84,214,783 93,617,292 9,402,509 11% 3.29 TOTAL GROSS REV. REQ. 124,955,795 143,123,515 18,167,721 15% 3.30 Less ATT. GG Adjustment 7,613,494 15,562,140 7,948,646 104% 3.30a Less ATT. MM Adjustment - N/A 3.31 GROSS REV. REQ. UNDER ATT. O 117,342,301 127,561,376 10,219,075 9%

Ameren Missouri June 2017 Calculation Net Revenue Requirement Page.Line Jun-16 Jun-17 Change Percent 1.1 Gross Revenue Requirement 117,342,301 127,561,376 10,219,075 9% 1.6 Total Revenue Credits 6,830,307 6,377,122 -453,185 -7% 1.6c Total Prior Period Adjustment (with interest) -1,571 605,636 607,207 -38651% 1.7 NET REVENUE REQUIREMENT 110,510,423 121,789,890 11,279,467 10% The Prior Period Adjustments for June 2016 relate to the FERC Audit Refund in Docket No. FA13-2-000 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

Ameren Missouri June 2017 Calculation AMMO Schedule 9 Rate Calculation Page.Line Jun-16 Jun-17 Change Percent 1.7 Net Revenue Requirement 110,510,423 121,789,890 11,279,467 10% 1.15 Ameren Missouri Divisor 6,518,000 6,317,790 (200,210) -3% Annual Cost ($/kW/Yr) 16.955 19.277 2.323 14% Network & P-to-P Rate ($/kW/Mo) 1.413 1.606 0.194 The divisor excludes the Southeast Missouri load included in the Entergy Arkansas, Inc. (EAI) pricing zone.

Ameren Missouri June 2017 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) 1,150,802,224 2 Net Transmission Plant - Total Attach O, p 2, line 14 and 23b col 5 (Note B) 823,265,384 O&M EXPENSE 3 Total O&M Allocated to Transmission Attach O, p 3, line 8 col 5 35,573,915 4 Annual Allocation Factor for O&M (line 3 divided by line 1 col 3) 3.09% GENERAL AND COMMON (G&C) DEPRECIATION EXPENSE 5 Total G&C Depreciation Expense Attach O, p 3, lines 10 & 11, col 5 (Note H) 1,177,700 6 Annual Allocation Factor for G&C Depreciation Expense (line 5 divided by line 1 col 3) 0.10% TAXES OTHER THAN INCOME TAXES 7 Total Other Taxes Attach O, p 3, line 20 col 5 10,840,667 8 Annual Allocation Factor for Other Taxes (line 7 divided by line 1 col 3) 0.94% 9 Annual Allocation Factor for Expense Sum of line 4, 6, and 8 4.14% INCOME TAXES 10 Total Income Taxes Attach O, p 3, line 27 col 5 20,442,429 11 Annual Allocation Factor for Income Taxes (line 10 divided by line 2 col 3) 2.48% RETURN 12 Return on Rate Base Attach O, p 3, line 28 col 5 49,506,223 13 Annual Allocation Factor for Return on Rate Base (line 12 divided by line 2 col 3) 6.01% 14 Annual Allocation Factor for Return Sum of line 11 and 13 8.50%

Ameren Missouri June 2017 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 $ 15,595,054 4.14% $644,945 $ 13,895,994 8.50% $1,180,672 $331,163 $2,156,780 $0 1b Reconductor Sioux-Huster-1 and -3 138 kV 1240 $ 15,620,832 $646,011 $ 13,425,767 $1,140,719 $404,149 $2,190,879 1c Gray Summit : 2nd 345/138 kV Transformer 2061 $ 22,410,810 $926,816 $ 19,844,108 $1,686,052 $407,469 $3,020,337 1d Lutesville: Northwest Cape 345/161 kV substation and new lines 2306 $ 58,585,316 $2,422,839 $ 57,718,016 $4,904,005 $867,300 $8,194,144 2 Annual Totals $15,562,140 3 Rev. Req. Adj For Attachment O

Significant transmission projects in 2016 and 2017 Completed in 2016 Project Name Total Cost Lutesville: Northwest Cape 345/161 kV substation and new lines $61 Million Viaduct-Cape Clark $24 Million Clark-Osage $41 Million To Be Completed in 2017 Project Name Total Cost Intelligrid $22 Million Sioux-Viele $7 Million Page-Mason CIP V5 $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/MarketsOperations/TransmissionSettlements/Pages/TransmissionPricing.aspx Ameren OASIS http://www.oasis.oati.com/AMRN/index.html MTEP 16 https://www.misoenergy.org/Planning/TransmissionExpansionPlanning/Pages/MTEP16.aspx MTEP 17 https://www.misoenergy.org/Planning/TransmissionExpansionPlanning/Pages/MTEP17.aspx Schedule 26 & 26-A Indicative Charges https://www.misoenergy.org/Planning/TransmissionExpansionPlanning/Pages/MTEPStudies.aspx