Document:

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                                                                 Exhibit 10.103

                            MIDWEST OP LEASE GUARANTY

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                            MIDWEST OP LEASE GUARANTY
                                     (T1)

                          Dated as of December 15, 1999

                                     made by

                             MIDWEST GENERATION, LLC
                                  as Guarantor

                                 Collins Station
                 Fossil Fuel-Fired Electric Generating Facility

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                          MIDWEST OP LEASE GUARANTY(T1)

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                            MIDWEST OP LEASE GUARANTY
                                      (T1)

         This MIDWEST OP LEASE GUARANTY (this "Guaranty"), dated as of December
15, 1999, is issued by MIDWEST GENERATION, LLC, a Delaware limited liability
company, as guarantor (the "Guarantor") in favor of the Beneficiary (as defined
in Section 4 below).

                                   WITNESSETH:

         WHEREAS, the Guarantor is an affiliate of Collins Holdings EME, LLC, a
Delaware limited liability company ("Collins Holdings").

         WHEREAS, simultaneously herewith Collins Holdings is entering into a
Participation Agreement (T1), dated as of December 15, 1999 (the "PARTICIPATION
AGREEMENT"), with Collins Trust I, (the "OWNER LESSOR"), Collins Generation I,
LLC (the "OWNER PARTICIPANT"), Wilmington Trust Company, not in its individual
capacity, except as expressly provided therein, but only as owner trustee (the
"OWNER TRUSTEE"), Edison Mission Midwest Holdings Co., the Guarantor, Midwest
Funding LLC, as lender, Bayerische Landesbank International S.A., as issuer of
the Midwest Letter of Credit, Bayerische Landesbank Girozentrale, as issuer of
the RCE Letter of Credit and Citibank, N.A., as Holder Representative;

         WHEREAS, the Beneficiary is the owner of the beneficial interest in
the Owner Lessor;

         WHEREAS, Collins Holdings intends to enter into a Facility Lease
Agreement (T1) dated as of December 15, 1999 (the "Facility Lease") with the
Owner Lessor;

         WHEREAS, Collins Holdings intends to enter into a Facility Site
Sublease Agreement (T1), dated as of December 15, 1999 (the "Facility Site
Sublease") with the Owner Lessor;

         WHEREAS, Collins Holdings intends to enter into a Facility Site
Sub-Sub-Lease Agreement (T1), dated as of December 15, 1999 (the "Facility Site
Sub-Sublease) with the Guarantor;

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         WHEREAS, it is a condition precedent to the parties' obligations under
the Participation Agreement that the Guarantor enter into and deliver this
Guaranty; and

         WHEREAS, the Guarantor anticipates benefitting directly and indirectly
from the transactions contemplated by the Participation Agreement, the Facility
Lease, the Facility Site Sublease and the Facility Site Sub-Sublease and is
executing and delivering this Guaranty to induce the Beneficiary to enter into
the Participation Agreement, and to induce the Owner Lessor to enter into the
Facility Lease, the Facility Site Sublease and the Facility Site Sub-Sublease.

         NOW, THEREFORE, in consideration of the foregoing and other benefits
accruing to the Guarantor, the receipt and sufficiency of which are hereby
acknowledged, the Guarantor agrees as follows:

SECTION 1. DEFINITIONS

         For purposes of this Guaranty, capitalized terms used but not otherwise
defined herein shall have the respective meanings specified in Appendix A to the
Participation Agreement. The general provisions of Appendix A shall apply to
terms used in this Guaranty and specifically defined herein. Any term defined by
reference to an agreement, instrument or other document shall have the meaning
so assigned to it whether or not such document is in effect.

SECTION 2. COVENANTS

         SECTION 2.1 Subject to the terms hereof, the Guarantor hereby
unconditionally and irrevocably guarantees, as primary obligor and not merely as
a surety, to the Beneficiary (a) the due, complete and punctual performance and
observance by Collins Holdings of each term, provision and condition binding
upon Collins Holdings pursuant to any of the Operative Documents to which
Collins Holdings is or becomes a party (the "CHE OPERATIVE DOCUMENTS") and (b)
the due, punctual and full payment (when and as the same may become due and
payable) of each amount that Collins Holdings is or may become obligated to pay
under or pursuant to any of the CHE Operative Documents, in accordance with the
terms thereof, by acceleration or otherwise without offset or deduction.

         SECTION 2.2 In the case of any failure by Collins Holdings to perform
and observe any such term, provision or condition after notice thereof by the
Beneficiary,

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the Guarantor agrees to cause such performance or observance to be
done, and in the case of any failure by Collins Holdings to make such payment as
and when the same shall become due and payable (by acceleration or otherwise),
the Guarantor hereby agrees to make such payment (and, in addition, such further
amounts, if any, as shall be sufficient to cover the costs and expenses of
collection hereunder); PROVIDED, nothing herein shall expand the aforesaid
obligations of the Guarantor beyond those of Collins Holdings under any of the
CHE Operative Documents.

         All such obligations and indebtedness set forth in Section 2.1 hereof
and this Section 2.2 are referred to in this Guaranty as the "OBLIGATIONS."

         SECTION 2.3 This Guaranty is a direct, independent and primary
obligation of the Guarantor and is an irrevocable, absolute, present,
unconditional and continuing obligation and guarantee of payment and performance
(and not merely of collection) and the validity and enforceability of this
Guaranty shall be absolute and is not conditioned in any way upon (a) the
institution of suit or the taking of any other action or any attempt to enforce
performance of or compliance with the obligations, covenants or undertakings
(including any payment obligations) of Collins Holdings, other than providing
notice to Collins Holdings, (b) the genuineness, validity, legality or
enforceability of any of the CHE Operative Documents or the lack of power or
authority of Collins Holdings to enter into any of the CHE Operative Documents
or any substitution, release or exchange of any other guaranty or any other
security for any of the Obligations or any other circumstance whatsoever (other
than payment or performance) that might otherwise constitute a legal or
equitable discharge or defense of a surety or guarantor, (c) any right of
set-off, recoupment or counterclaim, (d) any attempt to collect from Collins
Holdings or any other entity or to perfect or enforce any security or any other
condition or contingency or (e) any other action, occurrence or circumstance
whatsoever.

         SECTION 2.4 Without limiting the generality of the foregoing, the
Guarantor shall have no right to terminate this Guaranty, or to be released,
relieved or discharged from its obligations hereunder, and such obligations
shall be neither affected nor diminished for any reason whatsoever, including:

                  (i) any amendment or supplement to or modification of any of
                  the CHE Operative Documents, any extension or renewal of
                  Collins Holdings' obligations under any CHE Operative
                  Document, or any

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                  subletting, assignment or transfer of Collins
                  Holdings' or the Beneficiary's interest in the CHE Operative
                  Documents;

                   (ii) any bankruptcy, insolvency, readjustment, composition,
                  liquidation or any other change in the legal status of Collins
                  Holdings or any rejection or modification of the Obligations
                  of Collins Holdings or the Beneficiary as a result of any
                  bankruptcy, reorganization, insolvency or similar proceeding;

                  (iii) any furnishing or acceptance of additional security or
                  any exchange, substitution, surrender or release of any
                  security;

                  (iv) any waiver, consent or other action or inaction or any
                  exercise or nonexercise of any right, remedy or power with
                  respect to the Obligations or any of the CHE Operative
                  Documents;

                  (v) the unenforceability, lack of genuineness or invalidity of
                  the Obligations or any part thereof or the unenforceability,
                  lack of genuineness or invalidity of any agreement relating
                  thereto;

                  (vi) (A) any merger or consolidation of Collins Holdings or
                  the Guarantor into or with any other Person, (B) any change in
                  the structure of Collins Holdings, (C) any change in the
                  ownership of Collins Holdings or the Guarantor or (D) any
                  sale, lease or transfer of any or all of the assets of Collins
                  Holdings or the Guarantor to any other Person;

                  (vii) any default, misrepresentation, negligence, misconduct
                  or other action or inaction of any kind by the Beneficiary
                  under or in connection with any CHE Operative Document or any
                  other agreement relating to this Guaranty, except to the
                  extent that any such default, misrepresentation, negligence,
                  misconduct or other action or inaction would limit the
                  Obligations; or

                  (viii) any other circumstance whatsoever (except the complete
                  payment and performance of the Obligations), including,
                  without limitation, any act or omission of Collins Holdings or
                  the Beneficiary which changes the scope of the Guarantor's
                  risk.

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         SECTION 2.5 The Guarantor hereby unconditionally waives and releases,
to the extent permitted by law promptness, diligence and notice as to the
Obligations guaranteed hereby and acceptance of this Guaranty, and waives any
other circumstance which might otherwise constitute a defense available to, or a
discharge of, the Guarantor, including, without limitation, notice of default or
any failure on the part of Collins Holdings to perform and comply with any
Obligation and agrees that, except as otherwise provided herein, it shall not be
required to consent to or receive any notice of any amendment or modification
of, or waiver, consent or extension with respect to, the CHE Operative
Documents. No failure to exercise and no delay in exercising, on the part of the
Beneficiary, any right, power or privilege hereunder shall operate as a waiver
thereof, nor shall any single or partial exercise of any right, power or
privilege preclude any other or further exercise thereof, or the exercise of any
other power or right. The rights and remedies herein provided are cumulative and
not exclusive of any rights or remedies provided by law.

         SECTION 2.6 The Guarantor agrees to pay any costs and expenses incurred
by the other parties to the Participation Agreement in connection with the
enforcement of this Guaranty.

SECTION 3. GUARANTOR'S REPRESENTATIONS, WARRANTIES AND AGREEMENTS

                  In order to induce the Beneficiary to enter into the
Participation Agreement, and to induce the Owner Lessor to enter into the
Facility Lease, the Facility Site Sub-lease, the Facility Site Sub-Sublease, the
Guarantor represents and warrants unto the Beneficiary as set forth in this
Section III.

         SECTION 3.1 The Guarantor is duly organized, validly existing and in
good standing under the laws of its state of incorporation and has full
power, authority and legal right to execute, deliver and perform this
Guaranty.

         SECTION 3.2 The execution, delivery and performance by the Guarantor of
this Guaranty has been duly authorized by all necessary corporate action. This
Guaranty constitutes a legal, valid and binding obligation of the Guarantor
enforceable against the Guarantor in accordance with its terms, except as such
enforcement may be affected by applicable bankruptcy, insolvency, moratorium and
other similar laws affecting creditors' rights generally.

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SECTION 4. BENEFICIARY

         The Owner Participant, together with its affiliates, successors,
assigns, agents, members, partners, directors, officers or employees, is the
beneficiary of this Guaranty, but excluding in all cases the Owner Lessor (the
"BENEFICIARY").

SECTION 5. SURVIVAL OF GUARANTY

         Notwithstanding anything to the contrary herein, this Guaranty shall
continue to be effective or be reinstated, as the case may be, if at any time
any of the amounts paid to the Beneficiary, in whole or in part, is required to
be repaid upon the insolvency, bankruptcy, dissolution, liquidation, or
reorganization of the Guarantor, Collins Holdings or any other Person, or as a
result of the appointment of a custodian, interviewer, receiver, trustee, or
other officer with similar powers with respect to the Guarantor, Collins
Holdings or any other Person or with respect to any substantial part of the
property of the Guarantor, Collins Holdings or such other Person, all as if such
payments had not been made.

SECTION 6. REMEDIES; SUBROGATION

         SECTION 6.1 REMEDIES. In the event the Guarantor shall fail to pay
immediately any amounts due under this Guaranty, or to comply with any other
term of this Guaranty, the Beneficiary shall be entitled to all rights and
remedies to which it may be entitled hereunder or at law, in equity or by
statute.

         SECTION 6.2 SUBROGATION. The Guarantor will not exercise any rights
that it may acquire by way of subrogation under this Guaranty, by any payment
made hereunder or otherwise, until all of the Obligations shall have been paid
in full. If any amount shall be paid to the Guarantor on account of such
subrogation rights at any time when all of the Obligations shall not have been
paid in full, such amount shall be held in trust for the benefit of the
Beneficiary to whom such Obligation is payable and shall forthwith be paid to
such Beneficiary to be credited and applied to such Obligation, whether matured
or unmatured, in accordance with the terms of the Operative Document under which
such Obligation arose. If (i) the Guarantor shall make payment to the
Beneficiary of all or any part of the Obligations and (ii) all the Obligations
shall be paid in full, such Beneficiary will, at the Guarantor's request and
expense, execute and deliver to the Guarantor appropriate documents, without
recourse and with representation or warranty, necessary to evidence the transfer
by

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subrogation to the Guarantor of an interest in the Obligations resulting from
such payment by the Guarantor.

         SECTION 6.3 SURVIVAL OF REMEDIES AND SUBROGATION RIGHTS. The provisions
of this Section 6 shall survive the termination of this Guaranty and the payment
in full of the Obligations and the termination of the CHE Operative Documents.

SECTION 7. MISCELLANEOUS

         SECTION 7.1 AMENDMENTS AND WAIVERS. No term, covenant, agreement or
condition of this Guaranty may be terminated, amended or compliance therewith
waived (either generally or in a particular instance, retroactively or
prospectively) except by an instrument or instruments in writing executed by the
Guarantor and consented to by the Beneficiary.

         SECTION 7.2 NOTICES. Unless otherwise expressly specified or permitted
by the terms hereof, all communications and notices provided for herein shall be
in writing or by a telecommunications device capable of creating a written
record, and any such notice shall become effective (a) upon personal delivery
thereof, including by overnight mail or courier service, (b) in the case of
notice by United States mail, certified or registered, postage prepaid, return
receipt requested, upon receipt thereof, or (c) in the case of notice by such a
telecommunications device, upon transmission thereof, provided such transmission
is promptly confirmed by either of the methods set forth in clauses (a) or (b)
above, in each case addressed to the Guarantor hereto at its address set forth
below or at such other address as such party may from time to time designate by
written notice.

If to the Guarantor:

         Midwest Generation, LLC
         One Financial Place
         440 South LaSalle Street, Suite 3500
         Chicago, IL  60605
         Facsimile No.: (312) 583-6111
         Attention: Georgia R. Nelson

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         SECTION 7.3 SURVIVAL. Except as expressly set forth herein, the
warranties and covenants made by the Guarantor shall not survive the expiration
or termination of this Guaranty.

         SECTION 7.4 ASSIGNMENT AND ASSUMPTION. This Guaranty may not be
assigned by the Guarantor to, or assumed by, any successor to, or assignee of,
the Guarantor without the prior written consent of the Beneficiary.

         SECTION 7.5 GOVERNING LAW. This Guaranty shall be in all respects
governed by and construed in accordance with the laws of the State of New York,
including all matters of construction, validity and performance (without giving
effect to the conflicts of laws provisions, other than New York General
Obligations Law Section 5-1401).

         SECTION 7.6 SEVERABILITY. Any provision of this Guaranty that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

         SECTION 7.7 MERGER. This Guaranty constitutes the entire agreement and
supersedes all prior agreements and understandings, both written and oral
between or among the Guarantor, Collins Holdings and the Beneficiary with
respect to the subject matter hereof.

         SECTION 7.8 HEADINGS. The headings of the sections of this Guaranty are
inserted for purposes of convenience only and shall not be construed to affect
the meaning or construction of any of the provisions hereof.

         SECTION 7.9 FURTHER ASSURANCES. The Guarantor will promptly and duly
execute and deliver such further documents to make such further assurances for
and take such further action reasonably requested by the Beneficiary referred to
in Section 4 hereof to whom the Guarantor is obligated, all as may be reasonably
necessary to carry out more effectively the intent and purpose of this Guaranty.

         SECTION 7.10 EFFECTIVENESS OF GUARANTY. This Guaranty shall be
effective on the date of execution and delivery by the Guarantor.

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         IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be duly
executed and delivered by its officer thereunto duly authorized.

                                            MIDWEST GENERATION, LLC
                                            as Guarantor

                                            By:  /s/ Fred W. McCluskey
                                            --------------------------
                                            Name: Fred W. McCluskey
                                            Title: Vice President

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                                                                Exhibit 10.103.1

SCHEDULE IDENTIFYING SUBSTANTIALLY IDENTICAL AGREEMENT(S)  TO EXHIBIT 10.103

Midwest OP Lease Guaranty (T2), dated as of December15, 1999, made by Midwest
Generation, LLC.

Midwest OP Lease Guaranty (T3), dated as of December15, 1999, made by Midwest
Generation, LLC.

Midwest OP Lease Guaranty (T4), dated as of December15, 1999, made by Midwest
Generation, LLC.

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