Supplemental Trust Indenture dated as of February 1, 2024 between Northern States Power Company and The Bank of New York Mellon Trust Company, N.A., as successor Trustee, creating $700,000,000 aggregate principal amount of 5.40% First Mortgage Bonds, Series due March 15, 2054

Exhibit 4.01

SUPPLEMENTAL TRUST INDENTURE

FROM

NORTHERN STATES POWER COMPANY

(A MINNESOTA CORPORATION)

TO

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A.

DATED FEBRUARY 1, 2024

SUPPLEMENTAL TO TRUST INDENTURE

DATED FEBRUARY 1, 1937

AND

SUPPLEMENTAL AND RESTATED

TRUST INDENTURE

DATED MAY 1, 1988

TABLE OF CONTENTS

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Supplemental Trust Indenture, made effective as of the 1^st day of February, 2024, by and between NORTHERN STATES POWER COMPANY (formerly Northern Power Corporation), a corporation duly organized and existing under and by virtue of the laws of the State of Minnesota, having its principal office in the City of Minneapolis, Minnesota (the “Company”), party of the first part, and THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., a national banking association organized and existing under and by virtue of the laws of the United States, having a corporate trust office in the City of Chicago, Illinois (as successor trustee to Harris Trust and Savings Bank and BNY Midwest Trust Company), as trustee (the “Trustee”), party of the second part;

WITNESSETH:

WHEREAS, a predecessor in interest to the Company, Xcel Energy Inc. (formerly Northern States Power Company), a corporation duly organized and existing under and by virtue of the laws of the State of Minnesota (the “Predecessor Company”) has heretofore executed and delivered to the Trustee its Trust Indenture (the “1937 Indenture”), made as of February 1, 1937, whereby the Predecessor Company granted, bargained, sold, warranted, released, conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed to the Trustee and to its respective successors in trust, all property, real, personal and mixed then-owned or thereafter acquired or to be acquired by the Predecessor Company (except as therein excepted from the lien thereof) and subject to the rights reserved by the Predecessor Company in and by the provisions of the 1937 Indenture, to be held by said Trustee in trust in accordance with the provisions of the 1937 Indenture for the equal pro rata benefit and security of all and each of the bonds issued and to be issued thereunder in accordance with the provisions thereof; and

WHEREAS, the Predecessor Company heretofore has executed and delivered to the Trustee a Supplemental Trust Indenture, made as of June 1, 1942, whereby the Predecessor Company conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed to the Trustee, and its respective successors in said trust, additional property acquired by it subsequent to the date of the 1937 Indenture; and

WHEREAS, the Predecessor Company heretofore has executed and delivered to the Trustee the following additional Supplemental Trust Indentures which, in addition to conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee, and its respective successors in said trust, additional property acquired by it subsequent to the preparation of the next preceding Supplemental Trust Indenture and adding to the covenants, conditions and agreements of the 1937 Indenture certain additional covenants, conditions and agreements to be observed by the Predecessor Company, created the following series of First Mortgage Bonds:

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WHEREAS, on August 18, 2000, New Centuries Energies, Inc. was merged with and into the Predecessor Company and the Predecessor Company changed its corporate name from Northern States Power Company to Xcel Energy Inc.; and

WHEREAS, pursuant to an Assignment and Assumption Agreement dated as of August 18, 2000 between the Predecessor Company and the Company, substantially all the assets of the Predecessor Company (other than the stock of the Predecessor Company’s subsidiaries) were conveyed to, and substantially all the liabilities of the Predecessor Company, including liabilities created under the Indenture (as hereinafter defined), were assumed by, the Company (the “Assignment”); and

WHEREAS, pursuant to the Supplemental Trust Indenture dated as of August 1, 2000 among the Predecessor Company, the Company and Harris Trust and Savings Bank, as trustee, the requirements and conditions precedent set forth in the Original Indenture and the Restated Indenture (each as hereinafter defined) with respect to the Assignment were satisfied; and

WHEREAS, the Company heretofore has executed and delivered to the Trustee the following additional Supplemental Trust Indentures, which, in addition to conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee, and its respective successors in said trust, additional property acquired by it (or, as the case may be, the Predecessor Company) subsequent to the preparation of the next preceding Supplemental Trust Indenture and adding to the covenants, conditions and agreements of the 1937 Indenture certain additional covenants, conditions and agreements to be observed by the Company, created the following series of First Mortgage Bonds:

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WHEREAS, the 1937 Indenture and all of the foregoing Supplemental Trust Indentures are referred to herein collectively as the “Original Indenture”; and

WHEREAS, the Predecessor Company heretofore has executed and delivered to the Trustee a Supplemental and Restated Trust Indenture, dated May 1, 1988 which was recorded in the property records in various counties as set forth in Schedule B attached hereto (the “Restated Indenture”), which, in addition to conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee, and its respective successors in said trust, additional property acquired by it subsequent to the preparation of the next preceding Supplemental Trust Indenture, amended and restated the Original Indenture (except for those Supplemental Trust Indentures executed after May 1, 1988); and

WHEREAS, the Restated Indenture became effective and operative on July 20, 2005; and

WHEREAS, the Original Indenture, the Restated Indenture and all trust indentures supplemental thereto are referred to herein collectively as the “Indenture”; and

WHEREAS, pursuant to the Agreement of Resignation, Appointment and Acceptance dated as of May 1, 2002 among the Company, BNY Midwest Trust Company, as successor trustee, and Harris Trust and Savings Bank, BNY Midwest Trust Company accepted the rights, powers, duties and obligations of the trustee under the Indenture effective as of May 9, 2002; and

WHEREAS, pursuant to the Transfer and Assumption Agreement dated as of January 1, 2007 between BNY Midwest Trust Company and The Bank of New York Trust Company, N.A. (currently known as The Bank of New York Mellon Trust Company, N.A.), The Bank of New York Trust Company, N.A. accepted the rights, titles and interests of the trustee under the Indenture effective as of January 1, 2007; and

WHEREAS, the Indenture provides that bonds may be issued thereunder in one or more series, each series to have such distinctive designation as the Board of Directors of the Company may select for such series; and

WHEREAS, the Company is desirous of providing for the creation of a new series of First Mortgage Bonds, said new series of bonds to be designated “First Mortgage Bonds, Series due March 15, 2054” (the “Bonds”), the Bonds of such series to be issued as registered bonds without coupons in denominations of a multiple of $2,000 and integral multiples of $1,000 in excess thereof, and the Bonds of such series to be substantially in the form and of the tenor following with the redemption prices inserted therein in conformity with the provisions of Section 2.02 hereof, to-wit:

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(Form of Bonds)

NORTHERN STATES POWER COMPANY

(Incorporated under the laws of the State of Minnesota)

First Mortgage Bond

Series due March 15, 2054

[Unless this certificate is presented by an authorized representative of The Depository Trust Company, a New York corporation, to the Company or its agent for registration of transfer, exchange or payment, and any certificate issued is registered in the name of Cede & Co. or such other name as is requested by an authorized representative of The Depository Trust Company (and any payment is made to Cede & Co. or to such other entity as is requested by an authorized representative of The Depository Trust Company), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL since the registered owner hereof, Cede & Co., has an interest herein.]^*

NORTHERN STATES POWER COMPANY, a corporation organized and existing under the laws of the State of Minnesota (the “Company”), for value received, hereby promises to pay to Cede & Co. or its registered assigns, at the office of the Trustee, in the City of Chicago, Illinois, or, at the option of the registered owner, at the agency of the Company in the Borough of Manhattan, City and State of New York, an amount equal to [_____________] Dollars in lawful money of the United States of America, on the 15^th day of March, 2054 and to pay interest hereon from the date hereof at the rate of 5.40 percent per annum, in like money, until the Company’s obligation with respect to the payment of such principal sum shall be discharged; said interest being payable at the option of the person entitled to such interest either at the office of the Trustee, in Chicago, Illinois, or at the agency of the Company in the Borough of Manhattan, City and State of New York, on the 15^th day of March and on the 15^th day of September in each year, commencing on September 15, 2024 provided that as long as there is no existing default in the payment of interest and except for the payment of defaulted interest, the interest payable on any March 15 or September 15 will be paid to the person in whose name this bond was registered at the close of business on the record date (the March 1 prior to such March 15 or the September 1 prior to such September 15 (whether or not a business day)). If any interest payment date or date on which the principal of this bond is required to be paid is not a business day, then payment of principal, premium or interest need not be made on such date but may be made on the next succeeding business day with the same force and effect as if made on such interest payment date or date on which the principal of this bond is required to be paid and, in the case of timely payment thereof, no interest shall accrue for the period from and after such interest payment date or the date on which the principal of this bond is required to be paid. The term “business day” shall mean any day other than a Saturday or Sunday or a day on which the offices of the Trustee in the City of Chicago, Illinois, are closed pursuant to authorization of law.

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[EXCEPT UNDER THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, THIS GLOBAL BOND MAY NOT BE TRANSFERRED EXCEPT AS A WHOLE BY THE REGISTERED DEPOSITORY OR BY A NOMINEE OF THE REGISTERED DEPOSITORY TO THE REGISTERED DEPOSITORY, ANOTHER NOMINEE OF THE REGISTERED DEPOSITORY, A SUCCESSOR OF THE REGISTERED DEPOSITORY OR A NOMINEE OF SUCH SUCCESSOR.]^*

This bond is one of a duly authorized issue of bonds of the Company, of the series and designation indicated on the face hereof, which issue of bonds consists, or may consist, of several series of varying denominations, dates and tenor, all issued and to be issued under and equally secured (except insofar as a sinking fund, or similar fund, established in accordance with the provisions of the Indenture may afford additional security for the bonds of any specific series) by a Trust Indenture dated February 1, 1937 (the “1937 Indenture”), as supplemented by 72 supplemental trust indentures (collectively, the “Supplemental Indentures”), a Supplemental and Restated Trust Indenture dated May 1, 1988 (the “Restated Indenture”) and a new supplemental trust indenture for the bonds of this series (the “Supplemental Trust Indenture”), executed by the Company to THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A. (as successor trustee to Harris Trust and Savings Bank and BNY Midwest Trust Company), as trustee (the “Trustee”). The 1937 Indenture, as supplemented by the Supplemental Indentures, the Restated Indenture and the Supplemental Trust Indenture, is referred to herein as the “Indenture.” The Restated Indenture amends and restates the 1937 Indenture and certain of the Supplemental Indentures and became effective and operative on July 20, 2005. Reference hereby is made to the Indenture for a description of the property mortgaged and pledged, the nature and extent of the security, the rights of the holders of the bonds as to such security and the terms and conditions upon which the bonds may be issued under the Indenture and are secured. The principal hereof may be declared or may become due on the conditions, in the manner and at the time set forth in the Indenture upon the happening of a default as provided in the Indenture.

With the consent of the Company and to the extent permitted by and as provided in the Indenture, the rights and obligations of the Company and of the holders of the bonds and the terms and provisions of the Indenture and of any instruments supplemental thereto may be modified or altered by affirmative vote of the holders of at least 66 2/3% in principal amount of the bonds then outstanding under the Indenture and any instruments supplemental thereto (excluding bonds challenged and disqualified from voting by reason of the Company’s interest therein as provided in the Indenture); provided that without the consent of all holders of all bonds affected no such modification or alteration shall permit the extension of the maturity of the principal of any bond or the reduction in the rate of interest thereon or any other modification in the terms of payment of such principal or interest.

The Company and the Trustee may deem and treat the person in whose name this bond is registered as the absolute owner hereof for the purpose of receiving payment and for all other purposes and shall not be affected by any notice to the contrary.

Prior to September 15, 2053 (six months prior to the maturity date of the bonds of this series) (the “Par Call Date”), the Company may redeem the bonds of this series at its option, in whole or in part, at any time and from time to time, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) equal to the greater of:

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(1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the bonds of this series matured on the Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate (as defined below) plus 15 basis points less (b) interest accrued to the date of redemption, and

(2) 100% of the principal amount of the bonds of this series to be redeemed,

plus, in either case, accrued and unpaid interest thereon to, but excluding, the redemption date.

On or after the Par Call Date, the Company may redeem the bonds of this series at its option, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the bonds of this series being redeemed plus accrued and unpaid interest thereon to, but excluding, the redemption date.

“Treasury Rate” means, with respect to any redemption date, the yield determined by the Company in accordance with the following two paragraphs.

The Treasury Rate shall be determined by the Company after 4:15 p.m., New York City time (or after such time as yields on U.S. government securities are posted daily by the Board of Governors of the Federal Reserve System), on the third business day preceding the redemption date based upon the yield or yields for the most recent day that appear after such time on such day in the most recent statistical release published by the Board of Governors of the Federal Reserve System designated as “Selected Interest Rates (Daily)—H.15” (or any successor designation or publication) (“H.15”) under the caption “U.S. government securities–Treasury constant maturities–Nominal” (or any successor caption or heading) (“H.15 TCM”). In determining the Treasury Rate, the Company shall select, as applicable:

(1) the yield for the Treasury constant maturity on H.15 exactly equal to the period from the redemption date to the Par Call Date (the “Remaining Life”); or

(2) if there is no such Treasury constant maturity on H.15 exactly equal to the Remaining Life, the two yields—one yield corresponding to the Treasury constant maturity on H.15 immediately shorter than and one yield corresponding to the Treasury constant maturity on H.15 immediately longer than the Remaining Life—and shall interpolate to the Par Call Date on a straight-line basis (using the actual number of days) using such yields and rounding the result to three decimal places; or

(3) if there is no such Treasury constant maturity on H.15 shorter than or longer than the Remaining Life, the yield for the single Treasury constant maturity on H.15 closest to the Remaining Life. For purposes of this paragraph, the applicable Treasury constant maturity or maturities on H.15 shall be deemed to have a maturity date equal to the relevant number of months or years, as applicable, of such Treasury constant maturity from the redemption date.

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If on the third business day preceding the redemption date H.15 TCM is no longer published, the Company shall calculate the Treasury Rate based on the rate per annum equal to the semi-annual equivalent yield to maturity at 11:00 a.m., New York City time, on the second business day preceding such redemption date of the United States Treasury security maturing on, or with a maturity that is closest to, the Par Call Date, as applicable. If there is no United States Treasury security maturing on the Par Call Date but there are two or more United States Treasury securities with a maturity date equally distant from the Par Call Date, one with a maturity date preceding the Par Call Date and one with a maturity date following the Par Call Date, the Company shall select the United States Treasury security with a maturity date preceding the Par Call Date. If there are two or more United States Treasury securities maturing on the Par Call Date or two or more United States Treasury securities meeting the criteria of the preceding sentence, the Company shall select from among these two or more United States Treasury securities the United States Treasury security that is trading closest to par based upon the average of the bid and asked prices for such United States Treasury securities at 11:00 a.m., New York City time. In determining the Treasury Rate in accordance with the terms of this paragraph, the semi-annual yield to maturity of the applicable United States Treasury security shall be based upon the average of the bid and asked prices (expressed as a percentage of principal amount) at 11:00 a.m., New York City time, of such United States Treasury security, and rounded to three decimal places.

The Company’s actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error.

The Trustee shall have no duty to determine, or verify the calculation of, the redemption price.

Bonds of this series are not subject to a sinking fund.

This bond is transferable as prescribed in the Indenture by the registered owner hereof in person, or by his duly authorized attorney, at the office of the Trustee in the City of Chicago, Illinois, or at the option of the owner at the agency of the Company in the Borough of Manhattan, City and State of New York, or elsewhere if authorized by the Company, upon surrender and cancellation of this bond, and thereupon a new bond or bonds of the same series and of a like aggregate principal amount will be issued to the transferee in exchange therefor as provided in the Indenture, upon payment of taxes or other governmental charges, if any, that may be imposed in relation thereto.

Bonds of this series are interchangeable as to denominations in the manner and upon the conditions prescribed in the Indenture.

No charge shall be made by the Company for any exchange or transfer of bonds of this series, other than for taxes or other governmental charges, if any, that may be imposed in relation thereto.

The Company shall not be required to issue, transfer or exchange any bond of this series during a period of 10 days immediately preceding any selection of bonds of this series to be redeemed. The Company shall not be required to transfer or exchange any bond of this series called or being called for redemption in its entirety or to transfer or exchange the called portion of a bond of this series which has been called for partial redemption.

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No recourse shall be had for the payment of the principal of or the interest on this bond, or any part thereof, or of any claim based hereon or in respect hereof or of said Indenture, against any incorporator, or any past, present or future shareholder, officer or director of the Company or of any predecessor or successor corporation, either directly or through the Company, or through any such predecessor or successor corporation, or through any receiver or a trustee in bankruptcy, whether by virtue of any constitution, statute or rule of law or by the enforcement of any assessment or penalty or otherwise, all such liability being, by the acceptance hereof and as part of the consideration for the issue hereof, expressly waived and released, as more fully provided in the Indenture.

This bond shall not be valid or become obligatory for any purpose unless and until the certificate of authentication hereon shall have been signed by or on behalf of The Bank of New York Mellon Trust Company, N.A. (as successor trustee to Harris Trust and Savings Bank and BNY Midwest Trust Company), as Trustee under the Indenture, or its successor thereunder.

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IN WITNESS WHEREOF, NORTHERN STATES POWER COMPANY has caused this bond to be executed in its name by its President or a Vice President and its corporate seal, or a facsimile thereof, to be hereto affixed and attested by its Secretary or an Assistant Secretary.

(Form of Trustee’s Certificate)

This bond is one of the bonds of the Series designated thereon, described in the within-mentioned Indenture.

and

WHEREAS, the Company is desirous of conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee and to its respective successors in trust, additional property acquired by it subsequent to the date of the preparation of the Supplemental Trust Indenture dated as of May 1, 2023; and

WHEREAS, the Indenture provides in substance that the Company and the Trustee may enter into indentures supplemental thereto for the purposes, among others, of creating and setting forth the particulars of any new series of bonds and of providing the terms and conditions of the issue of the bonds of any series not expressly provided for in the Indenture and of conveying, assigning, transferring, mortgaging, pledging, setting over and confirming to the Trustee additional property of the Company, and for any other purpose not inconsistent with the terms of the Indenture; and

WHEREAS, the execution and delivery of this Supplemental Trust Indenture have been duly authorized by a resolution adopted by the Board of Directors of the Company; and

WHEREAS, the Trustee has duly determined to execute this Supplemental Trust Indenture and to be bound, insofar as it may lawfully do so, by the provisions hereof;

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Now, THEREFORE, Northern States Power Company, in consideration of the premises and of one dollar duly paid to it by the Trustee at or before the ensealing and delivery of these presents, the receipt of which is hereby acknowledged, and other good and valuable considerations, does hereby covenant and agree to and with The Bank of New York Mellon Trust Company, N.A. (as successor trustee to Harris Trust and Savings Bank and BNY Midwest Trust Company), as Trustee, and its successors in the trust under the Indenture for the benefit of those who hold or shall hold the bonds, or any of them, issued or to be issued thereunder, as follows:

ARTICLE I.

SPECIFIC SUBJECTION OF ADDITIONAL PROPERTY

TO THE LIEN OF THE INDENTURE

SECTION 1.01. The Company, in order to better secure the payment, of both the principal and interest, of all bonds of the Company at any time outstanding under the Indenture according to their tenor and effect and the performance of and compliance with the covenants and conditions contained in the Indenture, has granted, bargained, sold, warranted, released, conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed, and by these presents does grant, bargain, sell, warrant, release, convey, assign, transfer, mortgage, pledge, set over and confirm, to the Trustee and to its respective successors in said trust forever, subject to the rights reserved by the Company in and by the provisions of the Indenture, all of the property described and mentioned or enumerated in the schedule annexed hereto and marked Schedule A, reference to said schedule being made hereby with the same force and effect as if the same were incorporated herein at length; together with all and singular the tenements, hereditaments and appurtenances belonging and in any way appertaining to the aforesaid property or any part thereof with the reversion and reversions, remainder and remainders, tolls, rents and revenues, issues, income, products and profits thereof;

Also, in order to subject the personal property and chattels of the Company to the lien of the Indenture and to conform with the provisions of the Uniform Commercial Code, all fossil, nuclear, hydro and other electric generating plants, including buildings and other structures, turbines, generators, exciters, boilers, reactors, nuclear fuel, other boiler plant equipment, condensing equipment and all other generating equipment; substations; electric transmission and distribution systems, including structures, poles, towers, fixtures, conduits, insulators, wires, cables, transformers, services and meters; steam heating mains and equipment; gas transmission and distribution systems, including structures, storage facilities, mains, compressor stations, purifier stations, pressure holders, governors, services and meters; telephone plant and related distribution systems; trucks and trailers; office, shop and other buildings and structures, furniture and equipment; apparatus and equipment of all other kinds and descriptions; materials and supplies; all municipal and other franchises, leaseholds, licenses, permits, privileges, patents and patent rights; all shares of stock, bonds, evidences of indebtedness, contracts, claims, accounts receivable, choses in action and other intangibles, all books of account and other corporate records;

Excluding, however, all merchandise and appliances heretofore or hereafter acquired for the purpose of sale to customers and others;

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All the estate, right, title, interest and claim, whatsoever, at law as well as in equity, which the Company now has or hereafter may acquire in and to the aforesaid property and every part and parcel thereof subject, however, to the right of the Company, upon the occurrence and continuation of a Completed Default as defined in the Indenture, to retain in its possession all shares of stock, notes, evidences of indebtedness, other securities and cash not expressly required by the provisions hereof to be deposited with the Trustee, to retain in its possession all contracts, bills and accounts receivable, motor cars, any stock of goods, wares and merchandise, equipment or supplies acquired for the purpose of consumption in the operation, construction or repair of any of the properties of the Company, and to sell, exchange, pledge, hypothecate or otherwise dispose of any or all of such property so retained in its possession, free from the lien of the Indenture, without permission or hindrance on the part of the Trustee, or any of the bondholders. No person in any dealings with the Company in respect of any such property shall be charged with any notice or knowledge of any such Completed Default under the Indenture while the Company is in possession of such property. Nothing contained herein or in the Indenture shall be deemed or construed to require the deposit with, or delivery to, the Trustee of any of such property, except such as is specifically required to be deposited with the Trustee by some express provision of the Indenture;

To have and to hold all said property, real, personal and mixed, granted, bargained, sold, warranted, released, conveyed, assigned, transferred, mortgaged, pledged, set over or confirmed by the Company as aforesaid, or intended so to be, to the Trustee and its successors and assigns forever, subject, however, to Permitted Encumbrances and to the further reservations, covenants, conditions, uses and trusts set forth in the Indenture; in trust nevertheless for the same purposes and upon the same conditions as are set forth in the Indenture.

ARTICLE II.

FORM AND EXECUTION OF THE BONDS

SECTION 2.01. There is hereby created, for issuance under the Indenture, a series of bonds designated Series due March 15, 2054, which shall bear the descriptive title “First Mortgage Bonds, Series due March 15, 2054” (the Bonds), and the form thereof shall contain suitable provisions with respect to the matters hereafter specified in this Section. The Bonds may forthwith be executed by the Company substantially in the form set forth in the recitals, including the relevant provisions as indicated therein, and delivered to the Trustee for authentication and delivery by the Trustee in accordance with the provisions of the Indenture and this Supplemental Trust Indenture. The Bonds shall initially be authenticated and delivered in the aggregate principal amount of $700,000,000. The Bonds may be reopened and additional Bonds of said series may be issued in excess of the amount initially authenticated and delivered, provided that such additional Bonds of said series will contain the same terms (including the maturity date and interest payment terms), except for the price to the public and the issue date, and, if applicable, except for the initial interest payment date and initial interest accrual date, as the other Bonds. Any such additional Bonds, together with the Bonds initially authenticated, shall constitute a single series for purposes of the Indenture and shall be limited to an aggregate principal amount of $1,200,000,000. The Bonds shall mature on March 15, 2054, and shall be issued as registered bonds without coupons in denominations of $2,000, and integral multiples of $1,000 in excess thereof. The Bonds shall bear interest at a rate of 5.40% per annum on the principal amount thereof payable semi-annually on March 15 and September 15 of each year, commencing on September 15, 2024, and the principal shall be payable at the office of the Trustee in the City of Chicago, Illinois, or at the option of the registered owner at the agency of the Company in the Borough of Manhattan, City and State of New York, in lawful money of the United States of America, and the interest shall be payable in like money at the option of the

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person entitled to such interest either at said office of the Trustee in the City of Chicago, Illinois, or at the agency of the Company in the Borough of Manhattan, City and State of New York. Interest on the Bonds shall be calculated on the basis of a 360-day year consisting of twelve 30-day months. If any interest payment date or date on which the principal of this bond is required to be paid is not a business day, then payment of principal, premium or interest need not be made on such date but may be made on the next succeeding business day with the same force and effect as if made on such interest payment date or date on which the principal of this bond is required to be paid and, in the case of timely payment thereof, no interest shall accrue for the period from and after such interest payment date or the date on which the principal of this bond is required to be paid. The Bonds shall be dated as of the date of authentication thereof by the Trustee. The term “business day” shall mean any day other than a Saturday or Sunday or a day on which the offices of the Trustee in the City of Chicago, Illinois, are closed pursuant to authorization of law.

As long as there is no existing default in the payment of interest on the Bonds, the person in whose name any Bond is registered at the close of business on any Record Date with respect to any interest payment date shall be entitled to receive the interest payable on such interest payment date notwithstanding any transfer or exchange of any such Bond subsequent to the Record Date and on or prior to such interest payment date, except as and to the extent the Company shall default in the payment of the interest due on such interest payment date, in which case such defaulted interest shall be paid to the person in whose name such Bond is registered on the Special Record Date for the payment of such defaulted interest to be fixed by the Trustee, notice thereof shall be given to the registered holder of any Bond not less than 10 days prior to such Special Record Date, or may be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Bond may be listed, and upon such notice as may be required by such exchange.

The term “Record Date” as used in this Section 2.01 with respect to any interest payment date (March 15 or September 15) shall mean the March 1 prior to such March 15 or the September 1 prior to such September 15 (whether or not a business day).

As used in this Section 2.01, the term “default in the payment of interest” means failure to pay interest on the applicable interest payment date disregarding any period of grace permitted by the Indenture.

The “Special Record Date” as used in this Section 2.01 shall be fixed in the following manner. The Company shall notify the Trustee in writing of the amount of defaulted interest proposed to be paid on each Bond and the date of the proposed payment, and at the same time the Company shall deposit with the Trustee an amount of money equal to the aggregate amount proposed to be paid in respect of such defaulted interest or shall make arrangements satisfactory to the Trustee for such deposit prior to the date of the proposed payment, such money when deposited to be held in trust for the benefit of the persons entitled to such defaulted interest as provided in this Section 2.01. Thereupon the Trustee shall fix a Special Record Date for the payment of such defaulted interest which shall be not more than 15 nor less than 10 days prior to the date of the proposed payment and not less than 10 days after the receipt by the Trustee of the notice of the proposed payment. The Trustee shall promptly notify the Company of such Special Record Date and, in the name and at the expense of the Company, shall cause notice of the

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proposed payment of such defaulted interest and the Special Record Date therefor to be mailed, first class postage prepaid, to each holder of the Bonds, at his, her or its address as it appears in the bond register, not less than 10 days prior to such Special Record Date. Notice of the proposed payment of such defaulted interest and the Special Record Date therefor having been mailed as aforesaid, such defaulted interest shall be paid to the persons in whose names the Bonds are registered on such Special Record Date and shall not be payable pursuant to the paragraph immediately following in this Section 2.01.

The Company may make payment of any defaulted interest in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Bonds may be listed, and upon such notice as may be required by such exchange, if, after notice is given by the Company to the Trustee of the proposed payment pursuant to this Section 2.01, such payment shall be deemed practicable by the Trustee.

SECTION 2.02. Prior to September 15, 2053 (six months prior to the maturity date of the Bonds) (the “Par Call Date”), the Company may redeem the Bonds at its option, in whole or in part, at any time and from time to time, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) equal to the greater of

(1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the Bonds matured on the Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the Treasury Rate (as defined below) plus 15 basis points less (b) interest accrued to the date of redemption, and

(2) 100% of the principal amount of the Bonds to be redeemed,

plus, in either case, accrued and unpaid interest thereon to, but excluding, the redemption date.

On or after the Par Call Date, the Company may redeem the Bonds at its option, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the Bonds being redeemed plus accrued and unpaid interest thereon to, but excluding, the redemption date.

“Treasury Rate” means, with respect to any redemption date, the yield determined by the Company in accordance with the following two paragraphs.

The Treasury Rate shall be determined by the Company after 4:15 p.m., New York City time (or after such time as yields on U.S. government securities are posted daily by the Board of Governors of the Federal Reserve System), on the third business day preceding the redemption date based upon the yield or yields for the most recent day that appear after such time on such day in the most recent statistical release published by the Board of Governors of the Federal Reserve System designated as “Selected Interest Rates (Daily) – H.15” (or any successor designation or publication) (“H.15”) under the caption “U.S. government securities–Treasury constant maturities–Nominal” (or any successor caption or heading) (“H.15 TCM”). In determining the Treasury Rate, the Company shall select, as applicable:

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(1) the yield for the Treasury constant maturity on H.15 exactly equal to the period from the redemption date to the Par Call Date (the “Remaining Life”); or

(2) if there is no such Treasury constant maturity on H.15 exactly equal to the Remaining Life, the two yields—one yield corresponding to the Treasury constant maturity on H.15 immediately shorter than and one yield corresponding to the Treasury constant maturity on H.15 immediately longer than the Remaining Life—and shall interpolate to the Par Call Date on a straight-line basis (using the actual number of days) using such yields and rounding the result to three decimal places; or

(3) if there is no such Treasury constant maturity on H.15 shorter than or longer than the Remaining Life, the yield for the single Treasury constant maturity on H.15 closest to the Remaining Life. For purposes of this paragraph, the applicable Treasury constant maturity or maturities on H.15 shall be deemed to have a maturity date equal to the relevant number of months or years, as applicable, of such Treasury constant maturity from the redemption date.

If on the third business day preceding the redemption date H.15 TCM is no longer published, the Company shall calculate the Treasury Rate based on the rate per annum equal to the semi-annual equivalent yield to maturity at 11:00 a.m., New York City time, on the second business day preceding such redemption date of the United States Treasury security maturing on, or with a maturity that is closest to, the Par Call Date, as applicable. If there is no United States Treasury security maturing on the Par Call Date but there are two or more United States Treasury securities with a maturity date equally distant from the Par Call Date, one with a maturity date preceding the Par Call Date and one with a maturity date following the Par Call Date, the Company shall select the United States Treasury security with a maturity date preceding the Par Call Date. If there are two or more United States Treasury securities maturing on the Par Call Date or two or more United States Treasury securities meeting the criteria of the preceding sentence, the Company shall select from among these two or more United States Treasury securities the United States Treasury security that is trading closest to par based upon the average of the bid and asked prices for such United States Treasury securities at 11:00 a.m., New York City time. In determining the Treasury Rate in accordance with the terms of this paragraph, the semi-annual yield to maturity of the applicable United States Treasury security shall be based upon the average of the bid and asked prices (expressed as a percentage of principal amount) at 11:00 a.m., New York City time, of such United States Treasury security, and rounded to three decimal places.

The Company’s actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error.

The Trustee shall have no duty to determine, or verify the calculation of, the redemption price.

The Bonds are not subject to a sinking fund.

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The redemption price of the Bonds need not be specified in any temporary bond of said series if an appropriate reference be made in said temporary bond to the provision of this Section.

For purposes of Section 10.02 of the Indenture, the redemption price to be set forth in the notice of any redemption of the Bonds occurring prior to the Par Call Date may be the manner of calculation thereof. The Company shall give the Trustee notice of such redemption price promptly after the calculation thereof.

SECTION 2.03. The registered owner of any Bond or Bonds, at his, her or its option, may surrender the same with other Bonds of such series at the office of the Trustee in the City of Chicago, Illinois, or at the agency of the Company in the Borough of Manhattan, City and State of New York, or elsewhere if authorized by the Company, for cancellation, in exchange for other Bonds of such series of higher or lower authorized denominations, but of the same aggregate principal amount, bearing interest from its date, and upon receipt of any payment required under the provisions of Section 2.04 hereof. Thereupon the Company shall execute and deliver to the Trustee and the Trustee shall authenticate and deliver such other registered Bonds to such registered owner at its office or at any other place specified as aforesaid.

Notwithstanding any other provisions of the Indenture to the contrary, the Company shall not be required to issue, transfer or exchange any Bond of a series during a period of ten (10) days next preceding any selection of Bonds of such series to be redeemed. The Company shall not be required to transfer or exchange any Bond called or being called for redemption in its entirety or to transfer or exchange the called portion of a Bond which has been called for partial redemption.

SECTION 2.04. No charge shall be made by the Company for any exchange or transfer of Bonds other than for taxes or other governmental charges, if any, that may be imposed in relation thereto.

SECTION 2.05. The Bonds shall be executed on behalf of the Company by its President or one of its Vice Presidents, and its corporate seal shall be thereunto affixed, or printed, lithographed or engraved thereon, in facsimile, and attested by the signature of its Secretary or one of its Assistant Secretaries. Any such signatures may be manual or facsimile signatures and may be imprinted or otherwise reproduced. In case any of the officers who shall have signed any Bonds or attested the seal thereon shall cease to be such officers of the Company before the Bonds so signed and sealed actually shall have been authenticated by the Trustee or delivered by the Company, such Bonds nevertheless may be issued, authenticated and delivered with the same force and effect as though the person or persons who signed such Bonds and attested the seal thereon had not ceased to be such officer or officers of the Company. Any Bond issuable hereunder may be signed or attested on behalf of the Company by such person as at the actual date of the execution of such Bond shall be the proper officer of the Company, although at the date of such Bond such person shall not have been an officer of the Company.

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SECTION 2.06. (a) Except as provided in subsections (c) and (g) of this Section 2.06, the registered holder of all of the Bonds shall be The Depository Trust Company (“DTC”) and such Bonds shall be registered in the name of Cede & Co., as nominee for DTC. Payment of principal of, premium, if any, and interest on any Bonds registered in the name of Cede & Co. shall be made by transfer of New York Federal or equivalent immediately available funds with respect to the Bonds to the account of Cede & Co. on each such payment date for the Bonds at the address indicated for Cede & Co. in the bond register kept by the Trustee.

(b) The Bonds shall be initially issued in the form of one or more separate single authenticated fully registered certificates in the aggregate principal amount of all Bonds. Upon initial issuance, the ownership of such Bonds shall be registered in the bond register kept by the Trustee in the name of Cede & Co., as nominee of DTC. The Trustee and the Company may treat DTC (or its nominee) as the sole and exclusive registered holder of the Bonds registered in its name for the purposes of payment of the principal of, premium, if any, and interest on the Bonds and of giving any notice permitted or required to be given to holders under the Indenture, except as provided in subsection (g) below of this Section 2.06; and neither the Trustee nor the Company shall be affected by any notice to the contrary. Neither the Trustee nor the Company shall have any responsibility or obligation to any of DTC’s participants (each, a “Participant”), any person claiming a beneficial ownership in the Bonds under or through DTC or any Participant (each, a “Beneficial Owner”) or any other person which is not shown on the bond register maintained by the Trustee as being a registered holder, with respect to (1) the accuracy of any records maintained by DTC or any Participant; (2) the payment by DTC or any Participant of any amount in respect of the principal of, premium, if any, or interest on the Bonds; (3) the delivery by DTC or any Participant of any notice to any Beneficial Owner which is permitted or required to be given to registered holders under the Indenture of the Bonds; (4) the selection of the Beneficial Owners to receive payment in the event of any partial redemption of the Bonds; or (5) any consent given or other action taken by DTC as bondholder. The Trustee shall pay all principal of, premium, if any, and interest on the Bonds registered in the name of Cede & Co. only to or “upon the order of” (as that term is used in the Uniform Commercial Code as adopted in Minnesota and New York) DTC, and all such payments shall be valid and effective to fully satisfy and discharge the Company’s obligations with respect to the principal of, premium, if any, and interest on such Bonds to the extent of the sum or sums so paid. Except as otherwise provided in subsections (c) and (g) below of this Section 2.06, no person other than DTC shall receive authenticated bond certificates evidencing the obligation of the Company to make payments of principal of and interest on the Bonds. Upon delivery by DTC to the Trustee of written notice to the effect that DTC has determined to substitute a new nominee in place of Cede & Co., and subject to the provisions of the Indenture with respect to transfers of bonds, the word “Cede & Co.” in this Supplemental Trust Indenture shall refer to such new nominee of DTC.

(c) If the Company in its discretion determines that it is in the best interest of the Beneficial Owners that they be able to obtain bond certificates for the Bonds or there shall have occurred and be continuing a Completed Default with respect to the Bonds, the Company shall notify DTC and the Trustee, whereupon DTC will notify the Participants of the availability through DTC of bond certificates for Bonds. In such event, the Trustee shall issue, transfer and exchange bond certificates as requested by DTC in appropriate amounts pursuant to Article II of the Restated Indenture and Section 2.03 of this Supplemental Trust Indenture. The Company shall pay all costs in connection with the production of bond certificates if the Company makes such a determination under this Section 2.06(c). DTC may determine to discontinue providing its services with respect to the Bonds at any time by giving written notice to the Company and

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the Trustee and discharging its responsibilities with respect thereto under applicable law. Under such circumstances (if there is no successor book-entry depository), the Company and the Trustee shall be obligated (at the sole cost and expense of the Company) to deliver bond certificates for the Bonds as described in this Supplemental Trust Indenture. If bond certificates are issued, the provisions of the Indenture shall apply to, among other things, the transfer and exchange of such certificates and the method of payment of principal of, premium, if any, and interest on such certificates. Whenever DTC requests the Company and the Trustee to do so, the Company will direct the Trustee (at the sole cost and expense of the Company) to cooperate with DTC in taking appropriate action after reasonable notice (i) to make available one or more separate certificates evidencing the Bonds to any Participant or (ii) to arrange for another book-entry depository to maintain custody of certificates evidencing the Bonds registered in the name of such depository or its nominee. Any successor book-entry depository must be a clearing agency registered with the Securities and Exchange Commission pursuant to Section 17A of the Securities Exchange Act of 1934, as amended, and must enter into an agreement with the Company and the Trustee agreeing to act as the depository and clearing agency for the Bonds (except as provided in subsection (g) below of this Section 2.06). After such agreement has become effective, DTC shall present the Bonds for registration of transfer in accordance with Section 2.12 of the Restated Indenture, and the Trustee shall register them in the name of the successor book-entry depository or its nominee and all references thereafter to DTC shall be to such successor book-entry depository. If a successor book-entry depository has not accepted such position before the effective date of DTC’s termination of its services, the book-entry system shall automatically terminate and may not be reinstated without the consent of all registered holders of the Bonds.

(d) Notwithstanding any other provision of this Supplemental Trust Indenture to the contrary, so long as any Bonds are registered in the name of Cede & Co., as nominee of DTC, all payments with respect to the principal of, premium, if any, and interest on such Bonds and all notices with respect to such Bonds shall be made and given, respectively, to DTC as provided in the blanket representation letter between DTC and the Company. The Trustee is hereby authorized and directed to comply with all terms of the representation letter to the extent applicable to the Trustee.

(e) In connection with any notice or other communication to be provided pursuant to the Indenture for the Bonds by the Company or the Trustee with respect to any consent or other action to be taken by the registered holders of the Bonds, the Company or the Trustee, as the case may be, shall seek to establish a record date to the extent permitted by the Indenture for such consent or other action and give DTC notice of such record date not less than fifteen (15) calendar days in advance of such record date to the extent possible. Such notice to DTC shall be given only when DTC is the sole registered holder.

(f) NEITHER THE COMPANY NOR THE TRUSTEE WILL HAVE ANY RESPONSIBILITY OR OBLIGATIONS TO THE PARTICIPANTS OR THE BENEFICIAL OWNERS WITH RESPECT TO (1) THE ACCURACY OF ANY RECORDS MAINTAINED BY DTC OR ANY PARTICIPANT; (2) THE PAYMENT BY DTC OR ANY PARTICIPANT OF ANY AMOUNT DUE TO ANY BENEFICIAL OWNER IN RESPECT OF THE PRINCIPAL OF, PREMIUM, IF ANY, OR INTEREST ON THE BONDS; (3) THE DELIVERY BY DTC OR ANY PARTICIPANT OF ANY NOTICE TO ANY BENEFICIAL

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OWNER WHICH IS REQUIRED OR PERMITTED UNDER THE TERMS OF THE INDENTURE TO BE GIVEN TO REGISTERED HOLDERS; (4) THE SELECTION OF THE BENEFICIAL OWNERS TO RECEIVE PAYMENT IN THE EVENT OF ANY PARTIAL REDEMPTION OF THE BONDS; OR (5) ANY CONSENT GIVEN OR OTHER ACTION TAKEN BY DTC AS A REGISTERED HOLDER.

SO LONG AS CEDE & CO. IS THE REGISTERED HOLDER OF THE BONDS AS NOMINEE OF DTC, REFERENCES HEREIN TO REGISTERED HOLDERS OF THE BONDS SHALL MEAN CEDE & CO. AND SHALL NOT MEAN THE BENEFICIAL OWNERS OF THE BONDS NOR THE PARTICIPANTS.

(g) The Company, in its sole discretion, may terminate the services of DTC with respect to the Bonds if the Company determines that: (i) DTC (x) is unable to discharge its responsibilities with respect to the Bonds or (y) at any time ceases to be a clearing agency registered under the Securities Exchange Act of 1934, as amended; or (ii) there shall have occurred and be continuing a Completed Default with respect to the Bonds. The Company, in its sole discretion and subject to DTC’s procedures, may terminate the services of DTC with respect to the Bonds if the Company determines that a continuation of the requirement that all of the outstanding Bonds be registered with the registration books kept by the Trustee in the name of Cede & Co., as nominee of DTC, is not in the best interest of the Beneficial Owners of the Bonds. After such event and if no substitute book-entry depository is appointed by the Company, the bond certificates for the Bonds will be delivered as described in the Indenture.

(h) Upon the termination of the services of DTC with respect to the Bonds pursuant to subsections (c) or (g) of this Section 2.06 after which no substitute book-entry depository is appointed, the Bonds shall be registered in whatever name or names holders transferring or exchanging the Bonds shall designate in accordance with the provisions of the Indenture.

ARTICLE III.

APPOINTMENT OF AUTHENTICATING AGENT

SECTION 3.01. The Trustee shall, if requested in writing so to do by the Company, promptly appoint an agent or agents of the Trustee who shall have authority to authenticate registered Bonds in the name and on behalf of the Trustee. Such appointment by the Trustee shall be evidenced by a certificate of a vice-president of the Trustee delivered to the Company prior to the effectiveness of such appointment.

SECTION 3.02. (a) Any such authenticating agent shall be acceptable to the Company and at all times shall be a corporation, trust company or banking association organized and doing business under the laws of the United States or of any State, shall be authorized under such laws to act as authenticating agent, shall have a combined capital and surplus of at least $10,000,000 and shall be subject to supervision or examination by Federal or State authority. If such corporation, trust company or banking association publishes reports of condition at least annually, pursuant to law or to the requirements of the aforesaid supervising or examining authority, then for the purposes of this Section 3.02 the combined capital and surplus of such corporation shall be deemed to be its combined capital and surplus as set forth in its most recent report of condition so published.

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(b) Any corporation, trust company or banking association into which any authenticating agent may be merged or converted or with which it may be consolidated, or any corporation, trust company or banking association resulting from any merger, conversion or consolidation to which any authenticating agent shall be a party, or any corporation, trust company or banking association succeeding to the corporate agency business of any authenticating agent, shall continue to be the authenticating agent without the execution or filing of any paper or any further act on the part of the Trustee or the authenticating agent.

(c) Any authenticating agent at any time may resign by giving written notice of resignation to the Trustee and to the Company. The Trustee may at any time, and upon written request of the Company to the Trustee shall, terminate the agency of any authenticating agent by giving written notice of termination to such authenticating agent and to the Company. Upon receiving such a notice of resignation or upon such a termination, or in case at any time any authenticating agent shall cease to be eligible in accordance with the provisions of this Section 3.02, the Trustee, unless otherwise requested in writing by the Company, promptly shall appoint a successor authenticating agent, which shall be acceptable to the Company. Any successor authenticating agent upon acceptance of its appointment hereunder shall become vested with all the rights, powers, duties and responsibilities of its predecessor hereunder, with like effect as if originally named. No successor authenticating agent shall be appointed unless eligible under the provisions of this Section 3.02.

(d) The Company agrees to pay to any authenticating agent, appointed in accordance with the provisions of Section 3.01 and this Section 3.02, reasonable compensation for its services.

SECTION 3.03. If an appointment is made pursuant to this Article III, the registered Bonds shall have endorsed thereon, in addition to the Trustee’s Certificate, an alternate Trustee’s Certificate in the following form:

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(Form of Trustee’s Certificate)

This bond is one of the bonds of the Series designated thereon, described in the within-mentioned Indenture.

SECTION 3.04. No provision of this Article III shall require the Trustee to have at any time more than one such authenticating agent for any one State or to appoint any such authenticating agent in the State in which the Trustee has its principal place of business.

ARTICLE IV.

FINANCING STATEMENT TO COMPLY WITH

THE UNIFORM COMMERCIAL CODE

SECTION 4.01. The name and address of the debtor and secured party are set forth below:

NOTE: Northern States Power Company, the debtor above named, is “a transmitting utility” under the Uniform Commercial Code as adopted in Minnesota, North Dakota, South Dakota and Iowa.

SECTION 4.02. Reference to Article I hereof is made for a description of the property of the debtor covered by this Financing Statement with the same force and effect as if incorporated in this Section at length.

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SECTION 4.03. The maturity dates and respective principal amounts of obligations of the debtor secured and presently to be secured by the Indenture and this Supplemental Trust Indenture, reference to all of which for the terms and conditions thereof is hereby made with the same force and effect as if incorporated herein at length, are as follows:

SECTION 4.04. This Financing Statement is hereby adopted for all of the First Mortgage Bonds of the Series mentioned above secured by said Indenture and this Supplemental Trust Indenture.

SECTION 4.05. The 1937 Indenture, the Restated Indenture and the prior Supplemental Indentures, as set forth below, have been filed or recorded in each and every office in the States of Minnesota, North Dakota, South Dakota and Iowa designated by law for the filing or recording thereof in respect of all property of the Company subject thereto:

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SECTION 4.06. The property covered by this Financing Statement also shall secure additional series of First Mortgage Bonds of the debtor which may be issued from time to time in the future in accordance with the provisions of the Indenture.

ARTICLE V.

AMENDMENTS TO PROVISIONS OF RESTATED INDENTURE

SECTION 5.01. (a) Subject to Section 5.02 hereof, Section 1.03 of the Restated Indenture shall be amended to delete the definition of “Maintenance Fund” set forth therein.

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(b) Subject to Section 5.02 hereof, Section 5.03 of the Restated Indenture shall be amended and restated to read in its entirety as follows:

“SECTION 5.03. No Bonds shall be authenticated and delivered under the provisions of this Article V upon the basis of the acquisition or construction by the Company of any Permanent Additions until the Cost and Fair Value of such Permanent Additions shall have been certified to the Trustee as provided in Section 5.05. The aggregate principal amount of Bonds that may be authenticated and delivered under the provisions of this Article V is limited to 66-2/3% of the Cost or Fair Value, whichever is less, of the Permanent Additions forming the basis of the authentication and delivery thereof, provided that: (a) in each case, there shall be deducted from such Cost or Fair Value, as the case may be, the amounts removed from the fixed capital accounts of the Company as and for the Cost of any Retired Property during the period from February 1, 1937 to a date not more than 90 days preceding the date of authentication and delivery of the Bonds applied for; (b) in the case of Retired Property lost or destroyed by fire, or sold and released from the Lien of the Indenture, which is offset in whole or in part by cash, purchase money obligations deposited with the Trustee or property received in exchange for such Retired Property and made subject to the Lien of the Indenture, the amount deducted on account of such Retired Property shall be only the amount by which the Cost thereof shall exceed the aggregate amount of cash, the Fair Value of the purchase money obligations so deposited and the property received in such exchange; and (c) any such amounts which shall have been once deducted from the Cost or Fair Value of Permanent Additions included in any certificate previously delivered to the Trustee (including certificates delivered, prior to the Effective Date, pursuant to the Original Indenture or any Subsequent Supplemental Trust Indenture), for the authentication and delivery of Bonds, the withdrawal of cash or the release of property under any of the provisions of the Indenture, for the satisfaction of any sinking fund requirement relating to any series of Bonds, need not be deducted again on any such subsequent Application.

In no event shall the Indenture be construed to require the Company to deduct the Cost of Retired Property which was constructed, acquired or erected on or subsequent to February 1, 1937, but which has not at any time been included and may not after such time be included as a Permanent Addition in any Engineer’s Certificate delivered to the Trustee under subsection (a) of Section 5.05.”

(c) Subject to Section 5.02 hereof, Section 5.05 of the Restated Indenture shall be amended to delete subsections (iii) and (iv) of the first paragraph of such section.

(d) Subject to Section 5.02 hereof, Section 5.06(b) of the Restated Indenture shall be amended to delete the following: “, except to the extent permitted by Section 9.05.”

(e) Subject to Section 5.02 hereof, Section 5.07(d)(1) of the Restated Indenture shall be amended to delete the following: “(including any amounts attributable to subsection (b) of Section 9.05).”

(f) Subject to Section 5.02 hereof, Section 5.07(d)(8) of the Restated Indenture shall be amended to delete the following: “, except to the extent permitted by Section 9.05.”

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(g) Subject to Section 5.02 hereof, Section 6.01 of the Restated Indenture shall be amended and restated to read in its entirety as follows:

“SECTION 6.01. Subject to the provisions of Article IV, the Company may issue and the Trustee shall authenticate and deliver Bonds, in addition to those provided for in any other Section hereof, in an aggregate principal amount not exceeding the aggregate principal amount of any previously issued Bonds which shall have been retired, if the Trustee shall have received an Officer’s Certificate stating the aggregate principal amount of Bonds in respect of whose retirement the Bonds applied for in the accompanying Application are to be authenticated and delivered and that such retired Bonds do not include Bonds retired or used as subsequently specified in this Section 6.01; provided that no Bond shall be issued in respect of any such retired Bond (a) which shall have been retired (1) through the use of cash deposited with the Trustee pursuant to the provisions of Article VII, (2) through the use of cash constituting any part of the Release Fund or which pursuant to the Indenture is to be held or disposed of or applied in the same manner as moneys in the Release Fund, or (3) through the use of cash constituting a part of, or in lieu of the deposit of any such cash in, or through the operation of a sinking fund or other similar fund applicable to its retirement if the provisions establishing such sinking fund or other similar fund prohibit such issuance, or (b) whose retirement was previously used as a basis for the issuance of Bonds under this Section 6.01, or (c) which shall have been retired prior to the Effective Date and which the Company would not have been permitted under Section 1 of Article VI of the Original Indenture to use as a basis for the issuance of additional Bonds.”

(h) Subject to Section 5.02 hereof, ARTICLE IX of the Restated Indenture shall be deleted in its entirety.

SECTION 5.02. The holders of the Bonds shall have and be deemed to have approved and consented to the amendments set forth in Section 5.01 without the need for any further action or consent by such holder; however, such amendments shall not become effective until such time as there is no Bond Outstanding (as defined in the Restated Indenture) of any series created prior to the execution of this Supplemental Trust Indenture or when the requisite approvals under Section 18.02 of the Restated Indenture shall have been received.

ARTICLE VI.

MISCELLANEOUS

SECTION 6.01. The recitals of fact herein, except the recital that the Trustee has duly determined to execute this Supplemental Trust Indenture and be bound, insofar as it may lawfully so do, by the provisions hereof and in the Bonds shall be taken as statements of the Company and shall not be construed as made by the Trustee. The Trustee makes no representations as to the value of any of the property subject to the lien of the Indenture, or any part thereof, or as to the title of the Company thereto, or as to the security afforded thereby and hereby, or as to the validity of this Supplemental Trust Indenture or of the bonds issued under the Indenture by virtue hereof (except the Trustee’s certificate) and the Trustee shall incur no responsibility in respect of such matters.

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SECTION 6.02. This Supplemental Trust Indenture shall be construed in connection with and as a part of the Indenture.

SECTION 6.03. (a) If any provision of the Indenture or this Supplemental Trust Indenture limits, qualifies or conflicts with another provision of the Indenture required to be included in indentures qualified under the Trust Indenture Act of 1939, as amended (as enacted prior to the date of this Supplemental Trust Indenture) by any of the provisions of Sections 310 to 317, inclusive, of the said Act, such required provision shall control.

(b) In case any one or more of the provisions contained in this Supplemental Trust Indenture or in the Bonds issued hereunder shall be invalid, illegal or unenforceable in any respect, the validity, legality and enforceability of the remaining provisions contained herein and therein shall not in any way be affected, impaired, prejudiced or disturbed thereby.

SECTION 6.04. Wherever in this Supplemental Trust Indenture the word “Indenture” is used without the prefix “1937,” “Original,” “Restated,” or “Supplemental,” such word was used intentionally to include in its meaning both the 1937 Indenture, as amended and restated by the Restated Indenture, and all indentures supplemental thereto.

SECTION 6.05. Wherever in this Supplemental Trust Indenture either of the parties hereto is named or referred to, this shall be deemed to include the successors or assigns of such party, and all the covenants and agreements in this Supplemental Trust Indenture contained by or on behalf of the Company or by or on behalf of the Trustee shall bind and inure to the benefit of the respective successors and assigns of such parties, whether so expressed or not.

SECTION 6.06. (a) This Supplemental Trust Indenture may be executed simultaneously in several counterparts, and all said counterparts executed and delivered, each as an original, shall constitute but one and the same instrument.

(b) The Table of Contents and the descriptive headings of the several Articles of this Supplemental Trust Indenture were formulated, used and inserted in this Supplemental Trust Indenture for convenience only and shall not be deemed to affect the meaning or construction of any of the provisions hereof.

The total aggregate amount of obligations to be initially issued forthwith under this Supplemental Trust Indenture shall not exceed $700,000,000.

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IN WITNESS WHEREOF, on this 14^th day of February, A.D. 2024, NORTHERN STATES POWER COMPANY, a Minnesota corporation, party of the first part, has caused its corporate name to be hereunto affixed and this Supplemental Trust Indenture effective February 1, 2024, to be signed by its President or a Vice President, and attested by its Secretary or an Assistant Secretary, for and on its behalf, and THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A. (as successor trustee to Harris Trust and Savings Bank and BNY Midwest Trust Company), a national banking association, as Trustee, party of the second part, to evidence its acceptance of the trust hereby created, has caused its corporate name to be hereunto affixed, and this Supplemental Trust Indenture effective February 1, 2024, to be signed by its President, a Vice President or an Assistant Vice President.

[Signature page to Supplemental Indenture]

[Signature page to Supplemental Indenture]

This instrument was acknowledged before me on February 14, 2024 by Paul A. Johnson as Vice President, Treasurer, and Amy L. Schneider, as Vice President, Corporate Secretary, of Northern States Power Company, a Minnesota corporation, on behalf of the corporation.

On the 15^th day of February in the year 2024, before me, the undersigned, personally appeared, Michael C. Jenkins, a Vice President of The Bank of New York Mellon Trust Company, N.A., personally known to me or proved to me on the basis of satisfactory identification to be the individual whose name is subscribed to the within instrument and acknowledged to me that he executed the same in his capacity, and that by his signature on the instrument, the individual, or the person upon behalf of which the individual acted, executed the instrument.

SCHEDULE A

The property referred to in Article I of the foregoing Supplemental Trust Indenture from Northern States Power Company to The Bank of New York Mellon Trust Company N.A. as successor trustee to Harris Trust and Savings Bank, effective as of February 1, 2024, includes the following property hereafter more specifically described. Such description, however, is not intended to limit or impair the scope or intention of the general description contained in the granting clause or elsewhere in the Indenture.

I. PROPERTIES IN THE STATE OF MINNESOTA

Pine Bend RNG

Lot 1, Block 1, NSP Rich Valley Station

Wagon Wheel Substation

Lot 1, Block 1, Wagon Wheel, County of Houston, State of Minnesota.

Blazing Star I & II O&M Building

Property located in Lincoln County Minnesota, described as follows: Beginning at the Southeast corner of the Southwest Quarter (SW1/4) of Section Seventeen (17) in Township One Hundred Twelve (112) North, Range Forty-six (46) West of the 5^th P.M.; thence West along the South line of said Section Seventeen (17), a distance of Six Hundred Seventy Feet (670’); thence North, and at right angles, a distance of Two Hundred Sixty Feet (260’); thence East, parallel to the South line of said Section Seventeen (17) to a point on the East line of the Southwest Quarter (SW1/4) of Section Seventeen (17); thence South on and along the East line of the Southwest Quarter (SW1/4) of Section Seventeen (17) to the point of beginning.

Blazing Star I & II O&M Building (Additional)

Commencing at the Southeast corner of the Southwest Quarter of Section 17 in Township 112 North, Range 46 West of the 5^th P.M. Lincoln County, Minnesota; thence West along the South line of said Southwest Quarter of Section 17, a distance of 670 feet; thence North, and at right angles, a distance of 260 feet to the point of beginning; thence East parallel to said South line of the Southwest Quarter of Section 17 to a point on the East line of said Southwest Quarter of Section 17; thence North on and along said East line of said Southwest Quarter of Section 17 a distance of 50 feet; thence West parallel to said South line of the Southwest Quarter of Section 17 a distance of 675.30 feet; thence South at right angles to said South line of the Southwest Quarter of Section 17 a distance of 50 feet to the point of beginning.

A-1

Astro Substation

That part of the Southeast Quarter of Section 18, Township 117 North, Range 32 West, Meeker County, Minnesota, described as follows:

Beginning at the Northeast corner of the Southeast Quarter of said Section 18, Township 117 North, Range 32 West; thence South 00 degrees 16 minutes 42 seconds West along the East line of said Southeast Quarter, a distance of 872.16 feet to the Northerly line of the former Chicago and Northwestern Railroad right of way; thence North 63 degrees 11 minutes 12 seconds West along the Northerly line of said railroad right of way, a distance of 1433.76 feet; thence Northwesterly 704.17 feet to the North line of said Southeast Quarter, along a non-tangential curve, concave to the Southwest, having a radius of 2719.39 feet, a central angle of 14 degrees 50 minutes 11 seconds, a chord distance of 702.20 feet, the chord of said curve bears North 70 degrees 56 minutes 38 seconds West; thence South 89 degrees 53 minutes 11 seconds East along the North line of said Southeast Quarter, non tangent to the last described curve, a distance of 1947.56 feet to the point of beginning. Bearings and distances are based on the Meeker County Coordinate System, NAD83(2011), US Survey Feet.

St. Paul Service Center

Lot 1, Block 1, The Heights

(Torrens Certificate of Title No. 652626)

Nighthawk Substation

That part of the North Half of the Northeast Quarter of Section 4, Township 115 North, Range 36 West, Renville County, Minnesota, described as follows:

Commencing at the Northeast corner of said North Half of the Northeast Quarter, thence North 89 Degrees 49 Minutes 20 Seconds West along the north line of said North Half of the Northeast Quarter, a distance of 990.00 feet to the point of beginning; thence South 00 Degrees 26 Minutes 03 Seconds East and parallel with the East line of said North Half of the Northeast Quarter, a distance of 440.59 feet; thence South 89 Degrees 49 Minutes 20 Seconds East and parallel with the North line of said North Half of the Northeast Quarter, a distance of 500.29 feet; thence North 01 Degrees 58 Minutes 30 Seconds West, a distance of 440.88 feet to the North line of said North Half of the Northeast Quarter; thence North 89 Degrees 49 Minutes 20 Seconds West along said North line, a distance of 488.43 feet to the point of beginning.

A-2

Parkway Substation

The most westerly 300 feet of Outlot A, Energy Addition, Stearns County, Minnesota.

Gaitor Lake Substation

All that part of the North Half of the Northwest Quarter (N1/2 of NW1/4) of Section Twenty-seven (27), in Township One Hundred Seven (107) North of Range Twenty-two (22) West, Waseca County, Minnesota, described as follows:

Commencing at the northwest corner of said North Half of the Northwest Quarter; thence South 89 degrees 25 minutes 19 seconds East along the north line of said North Half of the Northwest Quarter, a distance of 801.53 feet to the point of beginning of the tract to be described; thence continuing South 89 degrees 25 minutes 19 seconds East along said north line, a distance of 467.00 feet; thence South 00 degrees 34 minutes 41 seconds West, a distance of 467.00 feet; thence North 89 degrees 25 minutes 19 seconds West, parallel to said north line, a distance of 467.00 feet; thence North 00 degrees 34 minutes 41 seconds East, a distance of 467.00 feet to said north line of said North Half of the Northwest Quarter and the point of beginning.

Waseca County, Minnesota

Abstract Property

Waseca Service Center

Lot 3, Block 1, South Industrial Park, Waseca County, Minnesota.

(Abstract Property)

II. PROPERTIES IN THE STATE OF NORTH DAKOTA

Turtle River Substation

That part of the Southeast Quarter (SE1/4) of Section 7, Township 151 North, Range 54 West of the 5^th Principal Meridian, Grand Forks County, North Dakota, described as follows:

A-3

Commencing at the southeast corner of said Southeast Quarter (SE1/4); thence North 02 degrees 03 minutes 57 seconds West along the east line of said Southeast Quarter (SE1/4), a distance of 200.02 feet to the point of beginning; thence continuing North 02 degrees 03 minutes 57 seconds West along the east line of said Southeast Quarter (SE1/4), a distance of 417.00 feet; thence South 87 degrees 52 minutes 08 seconds West, a distance of 492.00 feet; thence South 02 degrees 03 minutes 57 seconds East and parallel with the east line of said Southeast Quarter (SE1/4), a distance of 417.00 feet to the northerly right of way line of County Road 4; thence North 87 degrees 52 minutes 08 seconds East along the northerly right of way line of County Road 4, a distance of 492.00 feet to the point of beginning.

TRANSMISSION LINES OF THE COMPANY

The electric transmission lines of the Company, including towers, poles, pole lines, wires, switch racks, switchboards, insulators and other appliances and equipment, and all other property forming a part thereof or appertaining thereto, and all service lines extending therefrom; together with all rights for or relating to the construction, maintenance of operation thereof, through, over, under or upon any private property of public street or highway within as well as without the corporate limits of any municipal corporation, and particularly the following described lines, to wit:

I. IN THE STATE OF MINNESOTA

Line 0755

Yellow Medicine County

Section 4, Township 115 North, Range 39 West

Line 0808

Dakota County

Section 26, Township 28 North, Range 23 West

Line 0808

Ramsey County

Section 12, Township 28 North, Range 23 West

II. IN THE STATE OF SOUTH DAKOTA

Line 5503

Minnehaha County

Section 24, Township 101 North, Range 50 West

A-4

SCHEDULE B

Recording Information Regarding Supplemental and Restated Trust Indenture dated May 1, 1988

B-1

B-2

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