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                                                                    EXHIBIT 10.2

                                    AMENDED
                        ELECTRIC POWER SUPPLY AGREEMENT

                   Between Ameren Energy Generating Company

                                      And

                        Ameren Energy Marketing Company

THIS ELECTRIC POWER SUPPLY AGREEMENT (hereinafter "EPSA") made as of the 1st day
of May, 2000 and amended as of this 14th day of August, 2000 by and between
AMEREN ENERGY GENERATING COMPANY (hereinafter "Company" or "Genco") and AMEREN
ENERGY MARKETING COMPANY (hereinafter "Customer" or "Marketing") (Genco and
Marketing may be identified collectively as "Parties" or individually as a
"Party") is for the supply by Genco to Marketing of electric capacity and energy
available from Genco's electric generating units.

WHEREAS, Genco is a newly-formed generation-only company that has acquired all
electric generating units formerly owned and operated by Central Illinois Public
Service Company ("AmerenCIPS") and may acquire additional electric generating
units thereafter; and

WHEREAS, the electric generating units acquired by Genco from AmerenCIPS are and
will continue to be dispatched by an Agent designated for that purpose ("Agent")
pursuant to a Joint Dispatch Agreement ("JDA") between AmerenCIPS and Union
Electric Company ("AmerenUE"), subsequently amended among AmerenCIPS, AmerenUE
and Genco; and

WHEREAS, Marketing is or will be engaged in the business of purchasing and
reselling electric capacity and energy at wholesale and retail; and

WHEREAS, a portion of the capacity and energy supplied by Genco to Marketing
will be resold to AmerenCIPS for resale as bundled retail electric service
within its existing retail electric service area in Illinois at rates specified
by the Illinois Commerce Commission ("ICC") ("Bundled Sales"), or to wholesale
requirements customers of Marketing or retail customers of either Marketing
and/or AmerenCIPS that are allowed choice of an electric supplier under state
law at market-based prices ("Market Price Sales"); and

WHEREAS, Genco desires to sell and deliver to Marketing and Marketing desires to
purchase and receive from Genco capacity and energy available from the
generating units transferred by AmerenCIPS to Genco and from any additional
generating units that may be acquired by Genco in the future pursuant to the
rates, terms and conditions as amended and set forth herein;

NOW THEREFORE, in consideration for the agreements and undertakings established
herein and the mutual benefits derived therefrom, it is agreed as follows:
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1.       ELECTRIC CAPACITY AND ENERGY SERVICE

Genco shall make available or cause to be made available to Marketing all of the
electric capacity and energy which shall be available from the electric
generating units that have been transferred to Genco by AmerenCIPS and any
additional generating units that may be acquired by Genco in the future
(hereinafter "Power"), and Marketing shall purchase and pay for such Power in
accordance with the terms of this Agreement. The parties acknowledge the
existence of the JDA, and Genco's obligations associated therewith. To the
extent that (i) Marketing cannot resell the capacity and/or energy to which it
has the right and the obligation to purchase hereunder, and (ii) the Agent can
economically sell such capacity and/or energy, Marketing shall release its right
and shall be released from its obligation to purchase capacity and/or energy
under this EPSA equal to the amount of capacity and/or energy to be sold by the
Agent. Marketing shall coordinate with the Agent with respect to the scheduling
and dispatch of Power consistent with the JDA.

2.       TERM

Supply and delivery of Power pursuant to the original EPSA began on the Transfer
Date established in the Asset Transfer Agreement dated May 1, 2000 between Genco
and AmerenCIPS. The term of the Amended EPSA shall commence on the effective
date approved by the Federal Energy Regulatory Commission ("FERC") and shall
remain in effect until terminated by either Party upon at least one year's
written notice to the other Party; but in no event shall the EPSA be terminated
prior to 12:00 P.M. CPT on December 31, 2004.

3.       DELIVERY POINTS

All Power supplied under this EPSA that is provided by generation sources
acquired by Genco from AmerenCIPS shall be deemed to be delivered at the bus bar
connecting each such generation source to the AmerenCIPS transmission system
("Delivery Point A"). All Power supplied under this EPSA that is provided by
other generation sources shall be deemed to be delivered at the generation bus
("Delivery Point B;" collectively with Delivery Point A, hereinafter referred to
as "Points of Delivery"). Energy supplied under this EPSA shall be sixty (60)
hertz, three (3) phase alternating current.

4.       TRANSMISSION

Genco shall be responsible for making all necessary arrangements for
transmission and delivery of Power to the Points of Delivery identified above,
and for any communication with any transmission provider relating to the
transmission and delivery of Power to such Points of Delivery, including
communications concerning scheduling, tagging, displacements, disputes, or other
operational issues. Marketing shall cooperate with Genco for the purpose of
attaining the necessary transmission service and for implementing the
transmission service required for supplying the Power to the Points of Delivery.

5.       METERING

The Parties recognize that certain meters used to measure the amount of energy
supplied by Genco are owned by AmerenCIPS. In order that the accuracy of
registration is maintained in

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accordance with good utility practice, Marketing will provide for such metering
equipment to be tested by AmerenCIPS at suitable intervals. At the request of
Genco, Marketing shall arrange for special tests to be performed, but if less
than two-percent inaccuracy is found, Genco shall pay for the test. The expense
of all other tests shall be borne by Marketing.

If requested to do so, Marketing shall arrange for representatives of Genco to
be present at all routine or special tests or whenever any readings for the
purposes of settlements are taken from meters not having an automatic record. If
any test of metering equipment discloses an inaccuracy exceeding two percent,
the accounts of the Parties shall be adjusted for the period, not exceeding 90
days, that such inaccuracy is estimated to have existed. Should any metering
equipment fail to register, the amounts of energy delivered and demands
established shall be estimated from the best available data. Meters shall be
adjusted as nearly as practicable to 100.0% at the time of any meter tests, and
Marketing shall furnish a copy of any meter test results when requested by
Genco.

6.       SYSTEM PLANNING

In order for Marketing to be able to plan adequately to market and sell all of
the Power available from Genco, Genco shall notify Marketing no later than
November 1 of each year of the amount of Power it expects to have available in
each month of the next calendar year. Marketing shall provide Genco with its
initial annual capacity and energy forecast on or before December 1 for the next
calendar year. Marketing shall notify Genco of its updated capacity and energy
forecast on or before April 1 for the current year.

7.       RECORDS

Marketing shall provide Genco with all records that may reasonably be requested
by Genco for the purpose of administering this EPSA. The Parties shall keep such
records as may be needed to afford a clear history of all transactions under
this Agreement. The originals of all such records shall be retained by each
party for a minimum of three years and copies shall be delivered to the other
Party upon request.

8.       PRICES

         A.    Charges For Capacity and/or Energy Supplied To Customer For Sales
Other Than Market Price Sales

         1.    Capacity Charges
               ----------------

Each calendar year, Company will be compensated at a rate of $69,708/MWyr
("Rate") for the quantity ("Quantity") of capacity supplied, which shall be
equal to the greater of: (1) Customer's highest hourly capacity forecasted for
that year, or (2) Customer's actual annual peak demand ("Peak Demand"); minus
the portion of the forecasted or actual peak demand, as applicable, represented
by Market Price Sales. For the purpose of this provision, Customer's forecasted
and actual peak demand shall be adjusted for losses to the extent necessary to
be determined at the Points of Delivery.

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For capacity supplied by Company during the year ending December 31, 2000, the
annual capacity charge shall be calculated by multiplying the Quantity by the
Rate, and then multiplying the result by a fraction, (the numerator of which is
the number of days beginning with the Transfer Date and ending with December 31,
2000, and the denominator of which is 366.

Customer shall pay Company monthly for one-twelfth of the applicable annual
capacity charges for each calendar year during the Term hereunder (or a pro rata
share of such annual capacity charges during the year ending December 31, 2000)
based on Customer's forecasted peak demand. Within 10 days after the close of
each calendar year, Company shall calculate the Customer's capacity charges on
the basis of Customer's actual annual peak demand. In the event that Customer's
actual annual peak demand for such year exceeded its forecasted peak demand for
such year, Customer shall pay Company for any additional capacity charges that
are due with respect to such year at the time of payment of its next monthly
bill.

         2.   Energy
              ------

In addition to the capacity charges specified above, Customer shall pay Company
an energy charge of $21.8l/MWh for all energy supplied by Company to the Points
of Delivery for sale other than as Market Price Sales.

         B.   Charges for Energy and/or Capacity Supplied to Customer for Market
              ------------------------------------------------------------------
Price Sales
-----------

In addition to the charges for energy and/or capacity supplied to Customer as
set forth above, Customer shall pay Company all amounts received by Customer for
capacity and energy sold as Market Price Sales. Within 15 days following the
close of each calendar month, Customer shall advise Company of the estimated
amount of capacity and energy sold as Market Price Sales for such month and the
average rate per Mwh at which such capacity and/or energy was sold. Payments for
all such capacity and energy supplied to Customer for Market Price Sales shall
be remitted by Customer to Company in the month following the month in which
Customer receives payment for such capacity and energy. Within 45 days following
the close of each calendar month, Customer shall advise Company of the actual
amounts of Market Price Sales for such month, and the subsequent payments from
Customer to Company shall be adjusted accordingly.

9.       REGULATION

The Parties recognize that this EPSA is subject to regulation by the FERC
pursuant to Part II of the Federal Power Act. If the FERC should require the
modification of this EPSA prior to its acceptance, the Parties shall, in good
faith, attempt to reach agreement on modifications that would be acceptable to
the FERC in a manner that retains the economic benefits intended to be derived
by each party under this EPSA.

10.      PAYMENT OF BILLS

A.       BILLING FOR SERVICE: Bills for Power supplied to Marketing for sales
         other than Market Price Sales will be based upon the Quantity of
         capacity and amount of energy supplied by Genco at the Points of
         Delivery as set forth above. Within 15 days after the close of each
         calendar month, the Genco will issue the bill to Marketing
         electronically (commonly referred to as "EDI") or other suitable means.
         If Genco is unable to obtain

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         meter information or final Market Price Sales data is unavailable, an
         estimated bill will be issued, computed on the basis of Marketing's
         previous use together with such other information as is available. Once
         all billing information is considered final, the estimated bill will be
         adjusted and any payment due difference will be reflected on the next
         scheduled billing.

B.       PAYMENT PERIODS: The last date for payment of the "net amount" shown on
         the bill for Power supplied to Marketing for sales other than Market
         Price Sales shall be seven days after the date the EDI bill is issued
         (hereinafter "Net Payment Period"). Payment of all amounts for all
         Power supplied to Marketing for Market Price Sales shall be due on the
         same date. In the event of a disputed bill Marketing shall pay the
         undisputed portion within the Net Payment Period. When the last day of
         any Net Payment Period falls on a day other than a business day of
         Genco, such period will be automatically extended to include the next
         following business day. Genco's non-business days shall include
         Saturdays, Sundays, and the following holidays: New Year's day.
         Lincoln's Birthday, Washington's Birthday, Martin Luther King's
         Birthday, Good Friday, Memorial Day, Independence Day, Labor Day,
         Columbus Day, Veteran's Day, Thanksgiving day, Friday following
         Thanksgiving day, Christmas Eve (the last day of regular work schedule
         prior to Christmas day), Christmas day and New Year's Eve (the last day
         of regular work schedule prior to New Year's day). Whenever a holiday
         falls on Sunday the following Monday will not be considered a business
         day. Whenever a holiday falls on a Saturday, the prior Friday will not
         be considered a business day.

C.       PAYMENT AND LATE PAYMENTS: Marketing shall make payment to Genco by
         wire transfer, or other acceptable means, within the Net Payment Period
         in immediately available U.S. funds. When a bill is paid after the last
         date for payment in the "net amount" shown on the bill a late payment
         charge equivalent to one and one half (1 1/2) percent will be assessed
         each month on the unpaid balance.

11.      GOOD UTILITY PRACTICE

Genco shall operate and maintain each of the electric generating units and
appurtenant facilities that are transferred to it by AmerenCIPS or that it
subsequently acquires in good working order in compliance with all requirements
of any governmental agency and in accordance with good utility practice. Insofar
as practicable, Genco shall advise Marketing of any significant change in its
ability to supply Power to Marketing.

12.      INDEMNIFICATION

Marketing shall indemnify and save harmless and defend Genco from and against
any and all claims, demands, damages, costs or expenses arising, growing out of
or resulting in any manner from implementation of this EPSA.

13.      FORCE MAJEURE

In the event of Force Majeure, Genco shall notify Marketing immediately by oral
communication, confirmed in writing, of such occurrence, reporting the
commencement time and date, estimated duration, and estimated magnitude of the
reduction in capacity and/or energy

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deliveries resulting from the Force Majeure situation. Genco shall not be liable
for the failure to deliver the full amount or any part of the capacity and
energy to be supplied pursuant to this EPSA for the duration of the Force
Majeure. For the purpose of this provision, "Force Majeure" means an event or
circumstances which prevents Genco from performing its obligations under this
EPSA, which is not within the reasonable control of Genco, and which, by
exercise of due diligence, Genco is unable to overcome or avoid or cause to be
avoided. Force Majeure includes, but is not restricted to, fires, strikes, labor
stoppages, epidemics, floods, earthquakes, lightning storms, ice, acts of God,
riots, civil disturbances, civil war, invasion, insurrection, military or
usurped power, war, sabotage, explosions, failure of equipment or of contractors
or suppliers of materials or fuel, inability to obtain or ship material, fuel or
equipment because of the effect of similar causes on suppliers or carriers, or
an action or restraint by court order or public or governmental authority (so
long as the Genco has not applied for or assisted in the application for such
court or governmental action). Force Majeure shall not include Genco's ability
to sell capacity and/or energy to another purchaser at a more advantageous price
than that contained in this EPSA. The settlement of strikes, walkouts, lockouts,
and other labor disputes shall be entirely within the discretion of Genco, and
Genco may make settlement at such time and on such terms and conditions as it
may deem to be advisable. Interruption by a transmission provider shall not be
deemed to be an event of Force Majeure unless (i) Genco shall have made
arrangements with such transmission provider for the firm transmission, as
defined under the transmission provider's Open Access Transmission Tariff, of
the energy and (ii) such interruption is due to "force majeure" or
"uncontrollable force" or a similar term as defined under the transmission
provider's Open Access Transmission Tariff, and (iii) no other path is available
and no other remedy is available.

14.      ASSIGNMENT

This EPSA shall inure to the benefit of, and be binding upon, the respective
successors and assigns of Marketing and Genco. No assignment of this EPSA shall
be made by a Party except to a wholly-owned subsidiary or successor to
substantially all of that Party's business who assumes possession and operates
substantially the same facilities and business as the assignor. Notwithstanding
the foregoing, either Party shall be free to assign this EPSA to any of its
subsidiaries or affiliates, without the written consent of the other Party. The
assignment by a Party shall not relieve the Party, without the written consent
of the other Party, of any obligation to provide, or to accept and pay for, as
the case may be, the services contracted for hereunder.

15.      NOTICES

All notices to be given under this EPSA shall be in writing via First Class U.S.
mail, FAX or e-mail and shall be deemed given when sent. Notices shall be
addressed as set forth below, or to such other address as the party to be
notified may designate from time to time.

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         Notice to Genco:

         R. Alan Kelley
         Senior Vice President
         Ameren Energy Generating Company
         One Ameren Plaza
         1901 Chouteau Avenue
         St. Louis, MO 63103

         Notice to Marketing:

         Andrew M. Sem
         Vice President, Marketing and Sales
         Ameren Energy Marketing Company
         400 S. Fourth Street
         St. Louis, MO 63102

16.      WRITTEN MODIFICATION

Nothing contained herein shall be construed as affecting in any way the right of
Genco to unilaterally make application to the FERC for a change in rates and
charges under Section 205 of the Federal Power Act and pursuant to the
Commission's Rules and Regulations promulgated thereunder. Except with respect
to rates and charges, this EPSA shall not be modified except in writing by
amendment, executed by both parties, making express reference to the EPSA and
the specific provisions hereof modified or amended.

17.      LIMITS OF LIABILITY

IN THE EVENT OF LITIGATION UNDER THIS EPSA, THE PREVAILING PARTY SHALL BE
ENTITLED TO COMPENSATION FOR ANY REASONABLE ATTORNEYS FEES AND OTHER COSTS THAT
MAY BE INCURRED. UNLESS EXPRESSLY HEREIN PROVIDED, NEITHER PARTY SHALL BE LIABLE
FOR ANY CONSEQUENTIAL, INCIDENTAL, PUNITIVE, EXEMPLARY OR INDIRECT DAMAGES, LOST
PROFITS OR OTHER BUSINESS INTERRUPTION DAMAGES, BY STATUTE, IN TORT OR CONTRACT,
UNDER ANY INDEMNITY PROVISION OR OTHERWISE. IT IS THE INTENT OF THE PARTIES THAT
THE LIMITATIONS HEREIN IMPOSED ON REMEDIES AND THE MEASURE OF DAMAGES BE WITHOUT
REGARD TO THE CAUSE OR CAUSES RELATED THERETO, INCLUDING THE NEGLIGENCE OF ANY
PARTY, WHETHER SUCH NEGLIGENCE BE SOLE, JOINT OR CONCURRENT, OR ACTIVE OR
PASSIVE.

18.      DUTY TO MITIGATE

Each Party agrees that it has a duty to mitigate damages and covenants that it
will use commercially reasonable efforts to minimize any damages it may incur as
a result of the other Party's performance or non-performance of this EPSA.

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19.      WAIVERS

Any waiver at any time by either Genco or Marketing of its rights with respect
to a default under this EPSA or with respect to any other matter arising in
connection with this EPSA shall not be deemed a waiver with respect to any
subsequent default or matter. Any delay, short of the statutory period of
limitation, in asserting or enforcing any right under this EPSA shall not be
deemed a waiver of such right.

20.      ENTIRE AGREEMENT

This EPSA contains the entire agreement between the Parties in respect to the
subject matter contained herein, and there are no other understandings or
agreements between Genco and Marketing in respect thereof.

21.      WARRANTIES

The warranties expressly set forth in this EPSA are the sole warranties given by
either Party to the other Party in connection with the sale and purchase of
Power hereunder. EXCEPT AS SET FORTH HEREIN, GENCO EXPRESSLY NEGATES ANY OTHER
REPRESENTATION OR WARRANTY, WRITTEN OR ORAL, EXPRESSED OR IMPLIED, INCLUDING,
WITHOUT LIMITATION, ANY REPRESENTATION OR WARRANTY WITH RESPECT TO CONFORMITY TO
MODELS OR EXAMPLES, OR MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE.

22.      LIMITATION

This EPSA is not intended to and shall not create rights of any character
whatsoever in favor of any person, corporation, association, or entity other
than the parties to this EPSA, and the obligations herein assumed are solely for
the use and benefit of the parties to this EPSA, their successors in interest,
or assigns.

23.      SURVIVORSHIP OF OBLIGATIONS

The termination of this EPSA shall not discharge any Party from any obligation
it owed to the other Party under the EPSA by reason of any transaction, loss,
cost, damage, expense or liability which shall occur or arise prior to such
termination. It is the intent of the Parties that any such obligation owed
(whether the same shall be known or unknown as of the termination of this EPSA)
shall survive the termination of this EPSA. The Parties also intend that the
indemnification and limitation of liability provisions contained in this EPSA
shall remain operative and in full force and effect, regardless of any
termination of this EPSA, except with respect to actions or events occurring or
arising after such termination is effective.

24.      GOVERNING LAW

The interpretation and performance of this EPSA shall be in accordance with and
controlled by the laws of the State of Illinois (including any applicable orders
and regulations issued by the ICC), except as to matters governed by federal
statute.

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25.      SAVINGS CLAUSE

The provisions of this EPSA shall be interpreted where possible in a manner to
sustain their legality and enforcement. If at any time a provision of this EPSA
is found to be unenforceable, such provision shall be removed and the rest of
this EPSA shall remain intact and in effect as if the removed provision was
never contained therein.

26.      RESOLUTION OF DISPUTES

If a question or controversy arises between the Parties concerning the
observance or performance of any of the terms, provisions or conditions
contained herein or the rights or obligations of either Party under this EPSA,
such question or controversy shall in the first instance be the subject of a
meeting between the Parties to negotiate a resolution of such dispute. Such
meeting shall be held within fifteen (15) days of a request by either Party. If
within fifteen (15) days after that meeting, the Parties have not negotiated a
resolution or mutually extended the period of negotiation, either Party may seek
resolution of the question or controversy by arbitration, subject, however, to
any prohibition thereto by any governmental law or regulation.

The Party calling for arbitration ("Initiating Party") shall give written notice
to the other Party setting forth (a) a short and plain statement of the issue(s)
to be arbitrated; (b) a short and plain statement of the claim showing that the
Initiating Party is entitled to relief; and (c) a statement of the relief to
which the Initiating Party claims to be entitled. Such written notice including
sections (a), (b) and (c) defined above shall not exceed a document length of 20
pages, double spaced utilizing a font of 12. Within twenty (20) days from the
date of receipt of such notice, the other Party ("Receiving Party") may submit
its written response and give notice in the same manner required above of
additional issues to be arbitrated. The Initiating Party shall have twenty (20)
days to respond to any issues submitted for arbitration by the Receiving Party.

Within thirty (30) days of the date of the Initiating Party's written notice
requesting arbitration, each party shall designate a competent and disinterested
person to act as that party's designated arbitrator, with the two (2) persons
designated selecting a third neutral arbitrator within twenty (20) days of their
designation. In the event the first two (2) arbitrators cannot agree on a
mutually acceptable third arbitrator, they shall apply to the American
Arbitration Association ("AAA") to appoint the third arbitrator. The arbitration
shall be conducted pursuant to the Federal Rules of Civil Procedure, the Federal
Rules of Evidence, and the Commercial Arbitration Rules of the AAA.

Any decision and award of the majority of arbitrators shall be binding upon both
parties. The arbitrators shall not award any indirect, special, incidental or
consequential damages against either party. Judgment upon the award rendered may
be entered in any court of competent jurisdiction.

27.      HEADINGS

The descriptive headings of the sections of this EPSA have been inserted for
convenience of reference only and shall not modify or restrict any of the terms
and provisions thereof.

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IN WITNESS WHEREOF, the Parties hereto have caused this Amended EPSA to be
executed in duplicate, by its authorized officers, day and year first above
written.

AMEREN ENERGY                                   AMEREN ENERGY
MARKETING COMPANY                               GENERATING COMPANY



By:  /s/ James F. Whitsides                     By:  /s/ Gary L. Rainwater
    ------------------------------------            ----------------------------
     (Officer Signature)                             (Officer Signature)

     James F. Whitsides                              Gary L. Rainwater
    ------------------------------------            ----------------------------
     (Printed Name)                                  (Printed Name)

     President                                       President
    ------------------------------------            ----------------------------
     (Title)                                         (Title)

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