Supplemental Indenture



 EXHIBIT 4.1 
 This instrument was prepared by, 
 and when recorded should be 
 returned to: 
 Richard W. Astle 
 Sidley Austin LLP 
 Suite 3000 
 One South Dearborn
Street 
 Chicago, Illinois 60603 
  
  
 SUPPLEMENTAL
INDENTURE 
 Dated as of June 12, 2008 
 COMMONWEALTH EDISON COMPANY 
 to

 BNY MIDWEST TRUST COMPANY 
 and 
 D.G. DONOVAN 
 Trustees Under Mortgage Dated July 1, 1923, 
 and Certain 
 Indentures Supplemental Thereto 
 Providing for Issuance of 
 FIRST MORTGAGE BONDS, POLLUTION CONTROL SERIES 2008E 
 Due May 1, 2021 
  
  







 THIS SUPPLEMENTAL INDENTURE, dated as of June 12, 2008,
between COMMONWEALTH EDISON COMPANY, a corporation organized and existing under the laws of the State of Illinois (hereinafter called the “Company”) having an address at 440 South LaSalle
Street, Suite 3300, Chicago, Illinois 60605, party of the first part, BNY MIDWEST TRUST COMPANY, a trust company organized and existing under the laws of the State of Illinois having an address at 2 North
LaSalle Street, Suite 1020, Chicago, Illinois 60602, and D.G. DONOVAN, an individual having an address at 2 North LaSalle Street, Suite 1020, Chicago, Illinois 60602, as Trustee and Co-Trustee, respectively, under the Mortgage of
the Company dated July 1, 1923, as amended and supplemented by Supplemental Indenture dated August 1, 1944 and the subsequent supplemental indentures hereinafter mentioned, parties of the second part (said Trustee being hereinafter called
the “Trustee”, the Trustee and said Co-Trustee being hereinafter together called the “Trustees”, and said Mortgage dated July 1, 1923, as amended and supplemented by said Supplemental Indenture dated
August 1, 1944 and subsequent supplemental indentures, being hereinafter called the “Mortgage”), 
 W I T N E S S E T H:

 WHEREAS, the Company duly executed and delivered the Mortgage to provide for the issue of, and to secure, its bonds, issuable in series
and without limit as to principal amount except as provided in the Mortgage; and 
 WHEREAS, the Company from time to time has executed and
delivered supplemental indentures to the Mortgage to provide for (i) the creation of additional series of bonds secured by the Mortgage, (ii) the amendment of certain of the terms and provisions of the Mortgage and (iii) the
confirmation of the lien of the Mortgage upon property of the Company, such supplemental indentures that are currently effective and the respective dates, parties thereto and purposes thereof, being as follows: 
  

					
	 Supplemental
Indenture Date
	 	 Parties
	  	 Providing For

	August 1, 1944	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Edmond B. Stofft, as Trustee and Co-Trustee	  	Amendment and restatement of Mortgage dated July 1, 1923
			
	August 1, 1946	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Edmond B. Stofft, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 1, 1953	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Edmond B. Stofft, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	March 31, 1967	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Edward J. Friedrich, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 1, 1967	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Edward J. Friedrich, as Trustee and Co-Trustee	  	Amendment of Sections 3.01, 3.02, 3.05 and 3.14 of the Mortgage and issuance of First Mortgage 5-3/8% Bonds, Series Y

  

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	 Supplemental
Indenture Date
	 	 Parties
	  	 Providing For

	February 28, 1969	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	May 29, 1970	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	June 1, 1971	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 1, 1972	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	May 31, 1972	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	June 15, 1973	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	May 31, 1974	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	June 13, 1975	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	May 28, 1976	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	June 3, 1977	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	May 17, 1978	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	August 31, 1978	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	June 18, 1979	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	June 20, 1980	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 16, 1981	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien

  

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	 Supplemental
Indenture Date
	 	 Parties
	  	 Providing For

	April 30, 1982	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 15, 1983	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 13, 1984	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 15, 1985	 	Company to Continental Illinois National Bank and Trust Company of Chicago and Donald W. Alfvin, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 15, 1986	 	Company to Continental Illinois National Bank and Trust Company of Chicago and M.J. Kruger, as Trustee and Co-Trustee	  	Confirmation of mortgage lien
			
	April 15, 1993	 	Company to Continental Bank, National Association and M.J. Kruger, as Trustee and Co-Trustee	  	Issuance of First Mortgage 7-5/8% Bonds, Series 92
			
	June 15, 1993	 	Company to Continental Bank, National Association and M.J. Kruger, as Trustee and Co-Trustee	  	Issuance of First Mortgage 7% Bonds, Series 93 and First Mortgage 7-1/2% Bonds, Series 94
			
	January 15, 1994	 	Company to Continental Bank, National Association and M.J. Kruger, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 1994A, 1994B and 1994C
			
	March 1, 2002	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of unregistered First Mortgage 6.15% Bonds, Series 98
			
	May 20, 2002	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 2002
			
	June 1, 2002	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of additional unregistered First Mortgage 6.15% Bonds, Series 98
			
	October 7, 2002	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of registered First Mortgage 6.15% Bonds, Series 98 in exchange for unregistered First Mortgage 6.15% Bonds, Series 98
			
	January 13, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 3.700% Bonds, Series 99 and First Mortgage 5.875% Bonds, Series 100
			
	March 14, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 4.70% Bonds, Series 101
			
	April 23, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 2003

  

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	 Supplemental
Indenture Date
	 	 Parties
	  	 Providing For

	August 13, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 4.74% Bonds, Series 102
			
	September 10, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 2003B
			
	November 10, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 2003C
			
	December 5, 2003	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 2003D
			
	February 15, 2005	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage Bonds, Pollution Control Series 2005
			
	February 22, 2006	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 5.90% Bonds, Series 103
			
	August 1, 2006	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 5.95% Bonds, Series 104
			
	September 15, 2006	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of additional First Mortgage 5.95% Bonds, Series 104
			
	December 1, 2006	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 5.40% Bonds, Series 105
			
	March 1, 2007	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of additional First Mortgage 5.90% Bonds, Series 103
			
	August 30, 2007	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 6.15% Bonds, Series 106
			
	December 20, 2007	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Issuance of First Mortgage 6.45% Bonds, Series 107
			
	March 10, 2008	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Amendment of Section 15.06 of the Mortgage and issuance of First Mortgage 5.80% Bonds, Series 108
			
	April 23, 2008	 	Company to BNY Midwest Trust Company and D.G. Donovan, as Trustee and Co-Trustee	  	Amendment of Section 15.06 of the Mortgage and issuance of First Mortgage Bonds, Pollution Control Series 2008D and Series 2008F

 WHEREAS, the respective designations, maturity dates and principal amounts of the bonds of each
series presently outstanding under, and secured by, the Mortgage and the several supplemental indentures above referred to, are as follows: 
  

						
	Designation	  	 Maturity Date
	  	Principal Amount
	 First Mortgage 7-5/8% Bonds, Series 92
	  	April 15, 2013	  	$	125,000,000
	 First Mortgage 7-1/2% Bonds, Series 94
	  	July 1, 2013	  	 	127,000,000

  

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	Designation	  	 Maturity Date
	  	Principal Amount
	 First Mortgage 5.7% Bonds, Pollution Control Series 1994B
	  	January 15, 2009	  	 	15,900,000
	 First Mortgage 5.85% Bonds, Pollution Control Series 1994C
	  	January 15, 2014	  	 	17,000,000
	 First Mortgage 6.15% Bonds, Series 98
	  	March 15, 2012	  	 	450,000,000
	 First Mortgage Bonds, Pollution Control Series 2002
	  	April 15, 2013	  	 	100,000,000
	 First Mortgage 5.875% Bonds, Series 100
	  	February 1, 2033	  	 	253,600,000
	 First Mortgage 4.70% Bonds, Series 101
	  	April 15, 2015	  	 	260,000,000
	 First Mortgage Bonds, Pollution Control Series 2003
	  	May 15, 2017	  	 	40,000,000
	 First Mortgage 4.74% Bonds, Series 102
	  	August 15, 2010	  	 	212,000,000
	 First Mortgage Bonds, Pollution Control Series 2003B
	  	November 1, 2019	  	 	42,200,000
	 First Mortgage Bonds, Pollution Control Series 2003C
	  	March 1, 2020	  	 	50,000,000
	 First Mortgage Bonds, Pollution Control Series 2003D
	  	January 15, 2014	  	 	19,975,000
	 First Mortgage Bonds, Pollution Control Series 2005
	  	March 1, 2017	  	 	91,000,000
	 First Mortgage 5.90% Bonds, Series 103
	  	March 15, 2036	  	 	625,000,000
	 First Mortgage 5.95% Bonds, Series 104
	  	August 15, 2016	  	 	415,000,000
	 First Mortgage 5.40% Bonds, Series 105
	  	December 15, 2011	  	 	345,000,000
	 First Mortgage 6.15% Bonds, Series 106
	  	September 15, 2017	  	 	425,000,000
	 First Mortgage 6.45% Bonds, Series 107
	  	January 15, 2038	  	 	450,000,000
	 First Mortgage 5.80% Bonds, Series 108
	  	March 15, 2018	  	 	700,000,000
	 First Mortgage Bonds, Pollution Control Series 2008D
	  	March 1, 2020	  	 	50,000,000
	 First Mortgage Bonds, Pollution Control Series 2008F
	  	March 1, 2017	  	 	91,000,000
		  		  	 	 
		  	Total	  	$	4,904,675,000
		  		  	 	 

 WHEREAS, the Mortgage provides for the issuance from time to time thereunder, in series, of bonds
of the Company for the purposes and subject to the limitations therein specified; and 
 WHEREAS, the Company desires, by this Supplemental
Indenture, to create additional series of bonds to be issuable under the Mortgage, such bonds to be designated “First Mortgage Bonds, Pollution Control Series 2008E” (hereinafter called the “bonds of Series 2008E”), and
the terms and provisions to be contained in the bonds of Series 2008E or to be otherwise applicable thereto to be as set forth in this Supplemental Indenture; and 
 WHEREAS, the bonds of Series 2008E and the Trustee’s certificate to be endorsed thereon shall be substantially in the forms included in Exhibit A hereto; and 
  

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 WHEREAS, the Company is legally empowered and has been duly authorized by the necessary corporate action
and by order of the Illinois Commerce Commission to make, execute and deliver this Supplemental Indenture, and to create, as additional series of bonds of the Company, the bonds of Series 2008E, and all acts and things whatsoever necessary to make
this Supplemental Indenture, when executed and delivered by the Company and the Trustees, a valid, binding and legal instrument, and to make the bonds of Series 2008E, when authenticated by the Trustee and issued as provided in the Mortgage and in
this Supplemental Indenture, the valid, binding and legal obligations of the Company, entitled in all respects to the security of the Mortgage, as amended and supplemented, have been done and performed; 
 NOW, THEREFORE, in consideration of the premises and of the sum of one dollar duly paid by the Trustees to the Company, and for other good and valuable
consideration, the receipt of which is hereby acknowledged, the parties hereto do hereby agree as follows: 
 ARTICLE I 
 DEFINITIONS AND RULES OF CONSTRUCTION 
 SECTION 1.01. Terms of the Mortgage. The terms used in this Supplemental Indenture which are defined in the Mortgage, unless otherwise specified herein, are used herein with the same meanings as in the Mortgage. 
 SECTION 1.02. Definitions of New Terms. The following terms shall have the following meanings in this Supplemental Indenture: 
 “IFA” shall mean the Illinois Finance Authority, a political subdivision and body politic and corporate duly organized
and validly existing under and by virtue of the laws of the State of Illinois. 
 “IFA 2008E Bonds” shall
mean those certain Pollution Control Revenue Refunding Bonds (Commonwealth Edison Company Project) Series 2008E issued in the original aggregate principal amount of $49,830,000 under and pursuant to the terms of the IFA 2008E Indenture. 

“IFA 2008E Indenture” shall mean that certain Bond Indenture dated as of June 1, 2008, between IFA, as issuer,
and The Bank of New York Trust Company, N.A., as trustee, relating to the IFA 2008E Bonds. 
 SECTION 1.03. Rules of Construction. All
references to any agreement refer to such agreement as modified, varied, or amended from time to time by the parties thereto (including any permitted successors or assigns) in accordance with its terms. 
 ARTICLE II 
 SECTION 2.01. Designation and
Issuance of Bonds. The bonds of Series 2008E shall, as hereinbefore recited, be designated as the Company’s “First Mortgage Bonds, Pollution Control Series 2008E.” Subject to the provisions of the Mortgage, the bonds of Series
2008E shall be issuable without limitation as to the aggregate principal amount thereof. 
  

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 SECTION 2.02. Forms, Dates, Maturity Dates, Interest Rates and Interest Payment Dates of Bonds.
(a) The definitive bonds of Series 2008E shall be in engraved, lithographed, printed or type-written form and shall be registered bonds without coupons, and such bonds and the Trustee’s certificate to be endorsed thereon shall be
substantially in the forms included in Exhibit A hereto. The bonds of Series 2008E shall be dated as provided in Section 3.01 of the Mortgage, as amended by Supplemental Indenture dated April 1, 1967. All bonds of Series 2008E shall mature
on May 1, 2021. 
 (b) The bonds of Series 2008E shall bear interest on each day that they are outstanding at a rate per annum which is
equal to the weighted-average interest rate borne on the IFA 2008E Bonds outstanding on such date; provided, however, such interest rate on the bonds of Series 2008E shall not exceed 12% per annum. The bonds of Series 2008E shall
bear interest until the principal thereof shall be paid in full. Interest on the bonds of Series 2008E shall be payable to the record holder thereof on the dates that interest is payable on the IFA 2008E Bonds. 
 (c) The interest on the bonds of Series 2008E so payable on any interest payment date shall, subject to the exceptions provided in Section 3.01 of
the Mortgage, as amended by said Supplemental Indenture dated April 1, 1967, be paid to the person in whose name such bond is registered on such interest payment date. 
 SECTION 2.03. Bonds Issued as Collateral Security. The bonds of Series 2008E shall be issued, delivered, and pledged to, and registered in the
name of, the trustee under the IFA 2008E Indenture in order to secure and provide for, and as collateral security for, the due and punctual payment of the principal, premium, if any, and interest due from time to time on the IFA 2008E Bonds.

 SECTION 2.04. Credit for Payments on IFA Bonds. (a) The Company shall receive a credit against its obligation to make any
payment of interest on the bonds of Series 2008E, whether on an interest payment date, at maturity, upon redemption, upon acceleration or otherwise, in an amount equal to the amount, if any, paid by or for the account of the Company in respect of
any corresponding payment of interest on the IFA 2008E Bonds. So long as all the bonds of Series 2008E are pledged as described in Section 2.03, the obligation of the Company to make any payment with respect to the principal of the bonds of
Series 2008E shall be credited in full if, at the time that any such payment of principal shall be due, there shall have been paid by or for the account of the Company the then due principal of all IFA 2008E Bonds which are outstanding.
Notwithstanding the foregoing, a payment on the IFA 2008E Bonds made by a draw on a Credit Facility (as defined in the IFA 2008E Indenture) shall not be deemed a payment by or for the account of the Company unless and until the Company reimburses
the Credit Facility Provider (as defined in the IFA 2008E Indenture) for such draw, together with any accrued interest thereon, under the Credit Facility. 
 (b) The Trustee may conclusively presume that the obligation of the Company to pay the principal of, and premium, if any, and interest on, the bonds of Series 2008E as the same shall become due and payable has been
credited in accordance with this Section 2.04 unless and until it shall have received a written notice (including a telex, telegram, telecopy or other form of written telecommunication) from the trustee under the IFA 2008E Indenture stating
that 

  

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payment of the principal of, or premium, if any, or interest on, the IFA 2008E Bonds has become due and payable and has not been fully paid and specifying
the amount of funds required to make such payment. 
 SECTION 2.05. Execution of Bonds. The bonds of Series 2008E shall be executed on
behalf of the Company by its President or one of its Vice Presidents, manually or by facsimile signature, and shall have its corporate seal affixed thereto or a facsimile of such seal imprinted thereon, attested by its Secretary or one of its
Assistant Secretaries, manually or by facsimile signature, all as may be provided by resolution of the Board of Directors of the Company. In case any officer or officers whose signature or signatures, manual or facsimile, shall appear upon any bond
of Series 2008E shall cease to be such officer or officers before such bond shall have been actually authenticated and delivered, such bond nevertheless may be issued, authenticated and delivered with the same force and effect as though the person
or persons whose signature or signatures, manual or facsimile, appear thereon had not ceased to be such officer or officers of the Company. 
 SECTION 2.06. Medium and Places of Payment of Principal of, and Premium, If Any, and Interest on, Bonds; Transferability and Exchangeability. The principal of, and premium, if any, and the interest on the bonds of Series 2008E shall
be payable in any coin or currency of the United States of America which at the time of payment is legal tender for the payment of public and private debts, and such principal, premium, if any, and interest shall be payable at the office or agency
of the Company in the City of Chicago, State of Illinois, and such bonds shall be transferable and exchangeable, in the manner provided in Sections 3.09 and 3.10 of the Mortgage, at said office or agency. No charge shall be made by the Company to
the registered owner of any bond of Series 2008E for the registration of transfer of such bond or for the exchange thereof for bonds of the same series of other authorized denominations, except, in the case of any transfer, a charge sufficient to
reimburse the Company for any stamp or other tax or governmental charge required to be paid by the Company or the Trustee. 
 SECTION 2.07.
Denominations and Numbering of Bonds. The bonds of Series 2008E shall be issued in the denomination of $1,000 and in such multiples of $1,000 as shall from time to time hereafter be determined and authorized by the Board of Directors of the
Company or by any officer or officers of the Company authorized to make such determination, the authorization of the denomination of any bond of Series 2008E to be conclusively evidenced by the execution thereof on behalf of the Company. Bonds of
Series 2008E shall each be numbered R-1 and consecutively upwards. 
 SECTION 2.08. Temporary Bonds. Until definitive bonds of Series
2008E are ready for delivery, there may be authenticated and issued in lieu of any thereof and subject to all of the provisions, limitations, and conditions set forth in Section 3.11 of the Mortgage, temporary registered bonds of Series 2008E
without coupons. 
 SECTION 2.09. Optional Redemption of Bonds. Upon the notice and in the manner provided in Sections 4.01 and 4.03
of the IFA 2008E Indenture, the bonds of Series 2008E may be redeemed in whole or in part, at the option of the Company, on the date or dates determined under Section 4.01 of the IFA 2008E Indenture, at the redemption prices (expressed as
percentages of the principal amount of each bond of Series 2008E or portion thereof to be redeemed) set forth in Section 4.01 of the IFA 2008E Indenture, plus accrued interest to the redemption date. 
  

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 SECTION 2.10. Mandatory Redemption. Upon the notice and in the manner provided in
Section 4.11 of the IFA 2008E Indenture, the bonds of Series 2008E shall be redeemed by the Company in whole, or as provided under such paragraphs in part, at 100% of the principal amount thereof plus accrued interest to the redemption date.

 SECTION 2.11. Default Mandatory Redemption. The bonds of Series 2008E shall be redeemed promptly, without notice, by the Company in
whole at 100% of the principal amount thereof plus accrued interest to the date of redemption following receipt by the Trustee of written notice from the trustee under the IFA 2008E Indenture stating that the principal of the IFA 2008E Bonds has
been declared to be immediately due and payable as a result of an event of default under the IFA 2008E Indenture. 
 ARTICLE III 

AMENDMENT OF PROVISION OF MORTGAGE 
 Section 15.06 of the Mortgage shall be amended and restated to read in its entirety as follows: 
 SECTION
15.06. The Trustee and any successor to the Trustee may resign and be discharged from the trusts created by this Mortgage by giving notice thereof in writing to the Company, specifying the date when such resignation shall take effect, and by giving
notice thereof to the bondholders in the manner and to the extent provided under Section 15.10(c), and by publishing such notice at least once a week for three successive calendar weeks (the first such publication to be not less than thirty
days nor more than sixty days prior to the effective date of such resignation) in one authorized newspaper in the City of Chicago, State of Illinois, and in one authorized newspaper in the Borough of Manhattan, The City of New York, State of New
York. Subject to the provisions of Sections 15.04 and 15.05, such resignation shall take effect on the date specified in such notice unless previously a successor Trustee shall have been appointed as hereinafter provided, in which event such
resignation shall take effect upon the appointment of such successor Trustee. The Co-Trustee and any successor to the Co-Trustee may resign at any time and be discharged from the trusts hereby created by giving the Trustee and the Company notice in
writing of such resignation, specifying a date when such resignation shall take effect, which shall be at least thirty days after the giving of such notice. Such resignation shall, subject to the provisions of Sections 15.04 and 15.05, take effect
on the date specified in such notice unless previously a successor trustee shall have been appointed as hereinafter provided, in which event such resignation shall take effect immediately upon the appointment of such a successor trustee. 

Either of the Trustees or any successor trustee may be removed at any time by the holders of a majority in principal amount of the
bonds issued hereunder and at the time outstanding, upon payment to the trustee so removed of all moneys then due to it or him hereunder, by an instrument or concurrent instruments in writing, signed in duplicate by such holders. One copy shall be
filed with the Company and the other with the trustee so removed. 
  

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 The Co-Trustee and any successor to the Co-Trustee may be removed at any time by an
instrument in writing signed in duplicate by the Trustee, one copy of which shall be filed with the Company and the other delivered to the Co-Trustee so removed. 
 In case at any time either of the Trustees or any successor trustee shall resign, die, be dissolved or be removed or otherwise shall
become disqualified to act or incapable of acting, or in case control of the Trustee or of any successor trustee, or of its officers shall be taken over by any public officer or officers, a successor trustee may be appointed by the holders of a
majority in principal amount of the bonds issued hereunder and at the time outstanding by an instrument or concurrent instruments in writing signed in duplicate by such holders, and filed, one copy with the retiring trustee and the other with the
successor trustee, notification thereof being given to the Company by such successor trustee; but until a successor trustee shall be so appointed by the bondholders as herein authorized, the Company, by an instrument in writing, executed by order of
the Board of Directors, shall in any such case appoint a successor to the Trustee and the Trustee shall, by an instrument in writing in any such case, appoint a successor to the Co-Trustee. Every such successor to the Trustee so appointed by the
bondholders, by a court of competent jurisdiction or by the Company shall be a bank or trust company in good standing organized and doing business under the laws of the United States or of any State, having an office in the United States of America,
and (a) which shall be a corporation having a combined capital and surplus of not less than $5,000,000, (b) which shall be authorized under the laws of the jurisdiction of incorporation to exercise corporate trust powers, and
(c) which shall be subject to supervision or examination by a Federal or State authority. If such successor Trustee publishes reports of condition at least annually, pursuant to law or to the requirements of such supervising or examining
authority, the combined capital and surplus of such successor Trustee shall be deemed to be its combined capital and surplus as set forth in its most recent report of condition so published. Every such successor trustee appointed by the bondholders
or by the Trustee in succession to the Co-Trustee shall always be an individual, a citizen of the United States of America, unless otherwise required by law. 
 Anything hereinabove to the contrary notwithstanding, in case at any time the Co-Trustee, or any successor thereto, shall die, become
incapable of acting, resign or be removed, all the estates, properties, rights, powers, trusts, duties and obligations of the Trustees hereunder shall, to the extent permitted by law, vest in and be exercised by the Trustee, without the appointment
of a successor Co-Trustee. 
 If in a proper case no appointment of a successor to the Trustee or of a successor to the
Co-Trustee shall be made pursuant to the foregoing provisions of this Article XV within six months after a vacancy shall have occurred in the office of trustee, the holder of any bond or the retiring Trustee or Co-Trustee may apply to any court,
State or Federal having jurisdiction to appoint a successor trustee, and such court may thereupon, after such notice, if any, as such court may deem proper and prescribe, appoint a successor to the Trustee or to the Co-Trustee, as the case may be.

  

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 The holders of the bonds of Series 2008E shall be deemed to have approved the foregoing amendment;
however, the foregoing amendment shall not become effective until such time as it shall have received the requisite approvals under the provisions of the Mortgage. 
 ARTICLE IV 
 CONFIRMATION OF LIEN 
 The Company, for the equal and proportionate benefit and security of the holders of all bonds at any time issued under the Mortgage, hereby confirms the
lien of the Mortgage upon, and hereby grants, bargains, sells, transfers, assigns, pledges, mortgages, warrants and conveys unto the Trustees, all property of the Company and all property hereafter acquired by the Company, other than (in each case)
property which, by virtue of any of the provisions of the Mortgage, is excluded from such lien, and hereby confirms the title of the Trustees (as set forth in the Mortgage) in and to all such property. Without in any way limiting or restricting the
generality of the foregoing, there is specifically included within the confirmation of lien and title hereinabove expressed the property of the Company legally described on Exhibit B attached hereto and made a part hereof. 
 ARTICLE V 
 MISCELLANEOUS 
 The terms and conditions of this Supplemental Indenture shall be deemed to be a part of the terms and conditions of the Mortgage for any and all
purposes. The Mortgage, as supplemented by the indentures supplemental thereto dated subsequent to August 1, 1944 and referred to in the first paragraph of this Supplemental Indenture, and as further supplemented by this Supplemental Indenture,
is in all respects hereby ratified and confirmed. 
 This Supplemental Indenture shall bind and, subject to the provisions of Article XIV of
the Mortgage, inure to the benefit of the respective successors and assigns of the parties hereto. 
 Although this Supplemental Indenture is
dated as of June 12, 2008, it shall be effective only from and after the actual time of its execution and delivery by the Company and the Trustees on the date indicated by their respective acknowledgments hereto annexed. 
 Notwithstanding anything to the contrary contained in the Mortgage, the maximum amount of indebtedness secured by the Mortgage shall not exceed 200% of
the aggregate stated principal amount of the bonds of each series presently outstanding under, and secured by, the Mortgage, as set forth in the Recitals to this Supplemental Indenture, except to the extent such maximum amount may be adjusted by a
subsequent recorded supplemental indenture (which adjustment, and the corresponding supplemental indenture, shall not require the consent or approval of the holders of any bonds then outstanding under the Mortgage, including the holders of the bonds
of Series 2008E). 
  

 12 








 This Supplemental Indenture may be simultaneously executed in any number of counterparts, and all such
counterparts executed and delivered, each as an original, shall constitute but one and the same instrument. 
  

 13 








 IN WITNESS WHEREOF, Commonwealth Edison Company has caused this Supplemental Indenture to be executed in
its name by its Senior Vice President, Chief Financial Officer and Treasurer, and attested by its Secretary, and BNY Midwest Trust Company, as Trustee under the Mortgage, has caused this Supplemental Indenture to be executed in its name by one of
its Vice Presidents, and attested by one of its Vice Presidents, and D.G. Donovan, as Co-Trustee under the Mortgage, has hereunto affixed his signature, all as of the day and year first above written. 
  

			
	COMMONWEALTH EDISON COMPANY
		
	By:	 	 /s/ Robert K. McDonald

		 	Robert K. McDonald
		 	 Senior Vice President,
 Chief Financial
Officer and Treasurer



  

	
	ATTEST:
	
	 /s/ Donna Massey

	Donna Massey
	Secretary

  

			
	BNY MIDWEST TRUST COMPANY
		
	By:	 	 /s/ J. Bartolini

		 	J. Bartolini
		 	Vice President


  

	
	ATTEST:
	
	 /s/ M. Callahan

	M. Callahan
	Vice President

  

	
	 /s/ D.G. Donovan

	D.G. Donovan


  

 14 









					
	STATE OF ILLINOIS	 	)	  	
		 	)	  	
	COUNTY OF COOK	 	)	  	

 I, MARY E. NOLAN, a Notary Public in and for said County, in the State aforesaid, DO HEREBY
CERTIFY that Robert K. McDonald, Senior Vice President, Chief Financial Officer and Treasurer of Commonwealth Edison Company, an Illinois corporation, one of the parties described in and which executed the foregoing instrument, and Donna Massey,
Secretary of said corporation, who are both personally known to me to be the same persons whose names are subscribed to the foregoing instrument as such Senior Vice President, Chief Financial Officer and Treasurer and Secretary, respectively, and
who are both personally known to me to be Senior Vice President, Chief Financial Officer and Treasurer and Secretary, respectively, of said corporation, appeared before me this day in person and severally acknowledged that they signed, executed and
delivered said instrument as their free and voluntary act as such Senior Vice President, Chief Financial Officer and Treasurer and Secretary, respectively, of said corporation, and as the free and voluntary act of said corporation, for the uses and
purposes therein set forth. 
 GIVEN under my hand and notarial seal this
16th day of June, A.D. 2008. 
  

	
	 /s/ Mary E. Nolan

	Mary E. Nolan
	Notary Public


 (NOTARIAL SEAL) 
 My Commission expires April 23, 2009. 
  

 15 









					
	STATE OF ILLINOIS	 	)	  	
		 	)	  	
	COUNTY OF COOK	 	)	  	

 I, T. MOSTERD, a Notary Public in and for said County, in the State aforesaid, DO HEREBY CERTIFY
that J. BARTOLINI, Vice President of BNY Midwest Trust Company, an Illinois trust company, one of the parties described in and which executed the foregoing instrument, and M. CALLAHAN, Vice President of said trust company, who are both personally
known to me to be the same persons whose names are subscribed to the foregoing instrument as such Vice Presidents, and who are both personally known to me to be Vice Presidents of said trust company, appeared before me this day in person and
severally acknowledged that they signed, executed and delivered said instrument as their free and voluntary act as such Vice Presidents of said trust company, and as the free and voluntary act of said trust company, for the uses and purposes therein
set forth. 
 GIVEN under my hand and notarial seal this 12th day of June, A.D. 2008. 
  

	
	 /s/ T. Mosterd

	T. Mosterd
	Notary Public


 (NOTARIAL SEAL) 
 My Commission expires January 22, 2009. 
  

 16 









					
	STATE OF ILLINOIS	 	)	  	
		 	)	  	
	COUNTY OF COOK	 	)	  	

 I, T. MOSTERD, a Notary Public in and for said County, in the State aforesaid, DO HEREBY CERTIFY
that D.G. DONOVAN, one of the parties described in and which executed the foregoing instrument, who is personally known to me to be the same person whose name is subscribed to the foregoing instrument, appeared before me this day in person and
acknowledged that he signed, executed and delivered said instrument as his free and voluntary act for the uses and purposes therein set forth. 
 GIVEN under my hand and notarial seal this 12th day of June, A.D. 2008. 
  

	
	 /s/ T. Mosterd

	T. Mosterd
	Notary Public


 (NOTARIAL SEAL) 
 My Commission expires January 22, 2009. 
  

 17 








 EXHIBIT A 
 to 
 Supplemental Indenture 
 COMMONWEALTH EDISON COMPANY 
 First Mortgage Bond, Pollution Control Series 2008E

 Due May 1, 2021 
 COMMONWEALTH EDISON COMPANY, an Illinois corporation (hereinafter called the “Company”), for value received, hereby promises to pay to
                                         
   , as trustee under that certain Bond Indenture dated as of June 1, 2008 (the “IFA 2008E Indenture”) between Illinois Finance Authority (“IFA”) and said trustee, or registered assigns, on
the first day of May, 2021, the sum of              Dollars, and to pay interest on said sum from the date hereof until said sum shall be paid, at a rate per annum on each day
which is equal to the weighted-average interest rate borne on the IFA 2008E Bonds (as defined in the hereinafter referred to Supplemental Indenture) outstanding on such date, until the principal thereof shall be paid in full, subject to
Section 2.04 of the Supplemental Indenture dated as of June 12, 2008 (the “Supplemental Indenture”), executed and delivered by the Company to the Trustees (as hereinafter defined), which provides for certain credits
towards payment of principal of and interest on the bonds of this Series. Interest shall accrue on the bonds of this Series from the date of issuance hereof, and the payment thereof shall be credited as provided in Section 2.04(a) of the
Supplemental Indenture unless and until the Trustee receives the notice contemplated by Section 2.04(b) of the Supplemental Indenture, whereupon the interest on the bonds of this Series shall become and remain due and payable until such time as
the Trustee receives a further written notice (including a telex, telegram, telecopy or other form of written telecommunication) from the trustee under the IFA 2008E Indenture stating that such payments need not continue. When interest is due and
payable as described above, interest on the bonds of this Series shall be payable at the same time as interest on the IFA 2008E Bonds and upon maturity, redemption, or acceleration of the bonds of this Series, subject to Section 2.04 of the
Supplemental Indenture. The interest on each bond of this Series so payable on any interest payment date shall, subject to the exceptions provided in Section 3.01 of the Mortgage (as hereinafter defined), as amended by a supplemental indenture
dated April 1, 1967, be paid to the person in whose name such bond is registered on the date of such payment. The principal of, and premium, if any, and the interest on, this bond shall be payable at the office or agency of the Company in the
City of Chicago, State of Illinois in any coin or currency of the United States of America which at the time of payment is legal tender for the payment of public and private debts. 
 This bond is one of the bonds of the Company, issued and to be issued in series from time to time under and in accordance with and, irrespective of the
time of issue, equally and ratably secured by the Mortgage dated July 1, 1923, and indentures supplemental thereto, under which BNY Midwest Trust Company and D.G. Donovan (collectively, the “Trustees”) are now the Trustees, and
is one of the First Mortgage Bonds, Pollution Control Series 2008E of the 

  

 A-1 








 
Company, the issuance of which is provided for by the Supplemental Indenture, executed and delivered by the Company to such Trustees, to which Mortgage and
all indentures supplemental thereto reference is hereby made for a description of the property mortgaged and pledged, the nature and extent of the security, the rights of the holders and registered owners of said bonds, of the Company and of the
Trustees in respect of the security, and the terms and conditions governing the issuance and security of said bonds. The term “Mortgage,” as hereinafter used, shall mean said Mortgage dated July 1, 1923, and all indentures
supplemental thereto. 
 With the consent of the Company and to the extent permitted by and as provided in the Mortgage, modifications or
alterations of the Mortgage or of any indenture supplemental thereto and of the rights and obligations of the Company and of the holders and registered owners of the bonds may be made, and compliance with any provision of the Mortgage or any such
supplemental indenture may be waived, by the affirmative vote of the holders and registered owners of not less than eighty per centum (80%) in principal amount of the bonds then outstanding under the Mortgage, and by the affirmative vote
of the holders and registered owners of not less than eighty per centum (80%) in principal amount of the bonds of any series then outstanding under the Mortgage and affected by such modification or alteration, in case one or more but
less than all of the series of bonds then outstanding under the Mortgage are so affected, but in any case excluding bonds disqualified from voting by reason of the Company’s interest therein as provided in the Mortgage; subject, however, to the
condition, among other conditions stated in the Mortgage, that no such modification or alteration shall be made which will permit the extension of the time or times of payment of the principal of or the interest or the premium, if any, on this bond,
or the reduction in the principal amount hereof or in the rate of interest or the amount of any premium hereon, or any other modification in the terms of payment of such principal, interest or premium, which terms of payment are unconditional, or,
otherwise than as permitted by the Mortgage, the creation of any lien ranking prior to or on a parity with the lien of the Mortgage with respect to any of the mortgaged property, all as more fully provided in the Mortgage. 
 The bonds of this Series are subject to redemption, as provided in the Supplemental Indenture. 
 In case of certain completed defaults specified in the Mortgage, the principal of this bond may be declared or may become due and payable in the manner
and with the effect provided in the Mortgage. 
 No recourse shall be had for the payment of the principal of or the interest on this bond,
or for any claim based hereon, or otherwise in respect hereof or of the Mortgage, to or against any incorporator, stockholder, officer or director, past, present or future, of the Company or of any successor corporation, either directly or through
the Company or such successor corporation, under any constitution or statute or rule of law, or by the enforcement of any assessment or penalty, or otherwise, all such liability of incorporators, stockholders, directors and officers being waived and
released by the registered owner hereof by the acceptance of this bond and being likewise waived and released by the terms of the Mortgage, all as more fully provided therein. 
  

 A-2 








 This bond is transferable by the registered owner hereof, in person or by duly authorized attorney, at
the office or agency of the Company in the City of Chicago, State of Illinois, upon surrender and cancellation of this bond; and thereupon a new registered bond or bonds without coupons of the same aggregate principal amount and series will, upon
the payment of charges as provided in the Mortgage, be issued to the transferee in exchange herefor. 
 Bonds of this Series are issuable
only in registered form without coupons and in the denominations of $1,000 each and any authorized multiple thereof. As provided in the Mortgage, such bonds are exchangeable for registered bonds of the same series as between authorized
denominations. Any such exchange may be made by the registered owner of any such bond or bonds upon presentation thereof for that purpose at the office or agency of the Company in the City of Chicago, State of Illinois. 
 This bond shall not be entitled to any security or benefit under the Mortgage or be valid or become obligatory for any purpose unless and until it shall
have been authenticated by the execution by the corporate Trustee, or its successor in trust under the Mortgage, of the certificate endorsed hereon. 
  

 A-3 








 IN WITNESS WHEREOF, Commonwealth Edison Company has caused this bond to be executed in its name by its
President or one of its Vice Presidents, and has caused its corporate seal to be hereto affixed, attested by its Secretary or one of its Assistant Secretaries, as of the      day of
                    , 20    . 
  

					
	 	 	COMMONWEALTH EDISON COMPANY
			
	[SEAL]	 		 	
			
		 	By:	 	  

		 		 	President

 ATTEST: 
  

	
	  

	Secretary

 (General Form of Trustee’s Certificate) 
 This bond is one of the bonds of the series designated herein, referred to and described in the within mentioned Supplemental Indenture dated as of
June 12, 2008. 
  

					
		 	BNY MIDWEST TRUST COMPANY
			
		 	By:	 	  

		 		 	Authorized Officer

 Illinois Commerce Commission Identification No. 
  

 A-4 








 ABBREVIATIONS 
 The following abbreviations, when used in the inscription on the face of this instrument, shall be construed as though they were written out in full according to applicable laws or regulations: 
  

					
	TEN COM -	  	as tenants in common
		
	TEN ENT -	  	as tenants by the entireties
		
	JT TEN -	  	as joint tenants with right of survivorship and not as tenants in common


					
			
	UNIF GIFT MIN ACT -	  	Custodian	  	
		  	(Cust)	  	(Minors)
		  	under Uniform Gifts to Minors Act
		  	(State)	  	

 Additional abbreviations may also be used though not in the above list. 
 FOR VALUE RECEIVED the undersigned hereby sell(s), assign(s), and transfer(s) unto 
  

			
	PLEASE INSERT SOCIAL SECURITY OR	  	
	OTHER IDENTIFYING NUMBER OF ASSIGNEE	  	  


  
  
 (Please print or typewrite name and address including postal zip code of assignee) 
 the within Bond and all rights thereunder, hereby irrevocably constituting and appointing
                                        
attorney to transfer said Bond on the books of the Company, with full power of substitution in the premises. 
  

			
	Dated:
                                        
	  	  

		  	NOTICE: The signature to this assignment must correspond with the name as written upon the face of the within instrument in every particular, without alteration or enlargement or any change
whatever.

  

 A-5 








 EXHIBIT B 
 to 
 Supplemental Indenture 
 Legal Descriptions 
 [omitted] 
  

 B-1