QuickLinks -- Click here to rapidly navigate through this document

As filed with the Securities and Exchange Commission on January 8, 2008

Registration No. 333-134660



UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549


POST-EFFECTIVE AMENDMENT NO. 1
to
FORM S-3
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933


Xcel Energy Inc.
(Exact name of registrant as specified in its charter)

MINNESOTA
(State or jurisdiction of
incorporation or organization)
  41-0448030
(I.R.S. Employer Identification No.)
414 Nicollet Mall
Minneapolis, Minnesota 55401
(612) 330-5500
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

RICHARD C. KELLY
President and Chief Executive Officer
Xcel Energy Inc.
414 Nicollet Mall
Minneapolis, Minnesota 55401
(612) 330-5500

 

BENJAMIN G.S. FOWKE III
Vice President and Chief Financial Officer
Xcel Energy Inc.
414 Nicollet Mall
Minneapolis, Minnesota 55401
(612) 330-5500
(Names, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:
MICHAEL C. CONNELLY
Vice President and General Counsel
Xcel Energy Inc.
414 Nicollet Mall
Minneapolis, Minnesota 55401
(612) 330-5500
  ROBERT J. JOSEPH
Jones Day
77 West Wacker
Chicago, Illinois 60601
(312) 269-4176

Approximate date of commencement of proposed sale to the public:
From time to time after this registration statement becomes effective.


        If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box:    o

        If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box:    ý

        If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

        If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.    o

        If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.    ý

        If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.    ý


CALCULATION OF REGISTRATION FEE


Title of Each Class of Securities
to be Registered

  Amount to be Registered/
Proposed Maximum Offering Price Per Unit/
Proposed Maximum Aggregate Offering Price/
Amount of Registration Fee/


Junior Subordinated Debt Securities    
Senior Debt Securities    
Common Stock (par value $2.50 per share)   (2)
Rights to Purchase Common Stock (par value $2.50 per share)(1)    

(1)
One right to purchase common stock automatically trades with each share of common stock.
(2)
Indeterminate principal amounts of junior subordinated debt securities and senior debt securities and an indeterminate number of shares of common stock is being registered as may, from time to time, be offered at indeterminate prices. In accordance with Rules 456(b) and 457(r), the registrant is deferring payment of the registration fee for the securities offered by this Registration Statement.




PROSPECTUS

Xcel Energy Inc.

414 Nicollet Mall
Minneapolis, Minnesota 55401
(612) 330-5500

Senior Debt Securities
Junior Subordinated Debt Securities
Common Stock


        We may offer for sale, from time to time, either separately or together in any combination, the securities described in this prospectus. Each time we sell securities pursuant to this prospectus, we will provide a supplement to this prospectus that contains specific information about the offering and the specific terms of the securities offered. You should read this prospectus and the applicable prospectus supplement carefully before you invest. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement.

        Our common stock trades on the New York Stock Exchange under the symbol "XEL."


        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is January 8, 2008.


        As permitted under the rules of the Securities and Exchange Commission, this prospectus incorporates important business information about Xcel Energy Inc. that is contained in documents that we file with the Securities and Exchange Commission but that are not included in or delivered with this prospectus. You may obtain copies of these documents, without charge, from the website maintained by the Securities and Exchange Commission at www.sec.gov, as well as other sources. See "Where You Can Find More Information."

        You may also obtain copies of the incorporated documents, without charge, upon written or oral request to the Corporate Secretary, Xcel Energy Inc., 414 Nicollet Mall, Minneapolis, Minnesota 55401, (612) 330-5500.

        When we refer to "Xcel Energy," "our company," "we," "us" and "our" in this prospectus under the headings "Xcel Energy Inc." and "Ratio of Earnings to Fixed Charges," we mean Xcel Energy Inc. and its subsidiaries unless the context indicates otherwise. When such terms are used elsewhere in this prospectus, we refer only to Xcel Energy Inc. unless the context indicates otherwise.

        You should rely only on the information incorporated by reference or provided in this prospectus. We have not authorized anyone else to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this prospectus or the documents incorporated by reference is accurate as of any date other than the date on the front of those documents.


TABLE OF CONTENTS

Special Note Regarding Forward-Looking Statements   ii
Where You Can Find More Information   iii
Xcel Energy Inc.   1
Use of Proceeds   1
Ratio of Earnings to Fixed Charges   1
Description of Senior Unsecured Debt Securities   2
Description of Junior Subordinated Debt Securities   9
Book-Entry System   17
Description of Common Stock   20
Plan of Distribution   25
Legal Opinions   25
Experts   25

i



SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

        This prospectus and the documents it incorporates by reference contain statements that are not historical fact and constitute "forward-looking statements." When we use words like "anticipates," "believes," "estimates," "expects," "intends," "may," "plans," "should" or similar expressions, or when we discuss our strategy or plans, we are making forward-looking statements. Forward-looking statements are not guarantees of performance. They involve risks, uncertainties and assumptions. You are cautioned not to rely unduly on any forward-looking statements. Our future results may differ materially from those expressed in these forward-looking statements. These statements are necessarily based upon various assumptions involving judgments with respect to the future and other risks, including, among others:

ii


        These risks and uncertainties are discussed in more detail under "Business" and "Risk Factors" in our Annual Report on Form 10-K for the year ended December 31, 2006, under "Management's Discussion and Analysis" and "Notes to Consolidated Financial Statements" in our Current Report on Form 8-K/A filed on December 13, 2007 and under "Risk Factors," "Management's Discussion and Analysis" and "Notes to Consolidated Financial Statements" in our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2007 and our Quarterly Reports on Form 10-Q/A for the quarterly periods ended June 30, 2007 and September 30, 2007 and other documents on file with the Securities and Exchange Commission. You may obtain copies of these documents as described under "Where You Can Find More Information."

        We undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. The foregoing review of factors should not be construed as exhaustive.


WHERE YOU CAN FIND MORE INFORMATION

        We file annual, quarterly and special reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC's web site at http://www.sec.gov. You may also read and copy any document we file at the SEC's public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information on the public reference room.

        The SEC allows us to "incorporate by reference" the information we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings made with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Securities Exchange Act of 1934 from the time we file the initial registration statement until we sell all of the securities.

iii


        We are not required to, and do not, provide annual reports to holders of our debt securities unless specifically requested by a holder.

        You may request a copy of these filings at no cost, by writing or telephoning us at the following address:

iv



XCEL ENERGY INC.

        We are a public utility holding company with four major public utility subsidiaries: Northern States Power Company, a Minnesota corporation ("NSP-Minnesota"); Northern States Power Company, a Wisconsin corporation ("NSP-Wisconsin"); Public Service Company of Colorado, a Colorado corporation ("PSCo"); and Southwestern Public Service Company, a New Mexico corporation ("SPS"). NSP-Minnesota serves approximately 1.4 million electric customers and 0.5 million gas customers in Minnesota, North Dakota and South Dakota. NSP-Wisconsin serves approximately 245,000 electric customers and 100,000 gas customers in northern Wisconsin and Michigan. PSCo serves approximately 1.3 million electric customers and approximately 1.3 million gas customers in Colorado. SPS serves approximately 386,000 electric customers in portions of Texas and New Mexico. We also have several non-utility subsidiaries, including Eloigne Co., which invests in rental housing projects that qualify for low-income tax reported credits.

        We were incorporated in 1909 under the laws of Minnesota as Northern States Power Company. On August 18, 2000, we merged with New Century Energies, Inc. and our name was changed from Northern States Power Company to Xcel Energy Inc. Our principal executive offices are located at 414 Nicollet Mall, Minneapolis, Minnesota 55401 and our telephone number is (612) 330-5500.

        This prospectus is part of a registration statement that we filed with the SEC utilizing a "shelf" registration process. Under this shelf process, we may sell any combination of the securities described in this prospectus in one or more offerings.

        This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or supplement information contained in this prospectus. You should read this prospectus and the related exhibits filed with the SEC and any prospectus supplement together with additional information described under the heading "Where You Can Find More Information."


USE OF PROCEEDS

        We will add the net proceeds from the sale of the securities described in this prospectus to our general funds and use those proceeds for general corporate purposes, primarily to fund our operating units and subsidiaries, and to repay debt. The specific allocation of the proceeds of a particular series of the securities will be described in the prospectus supplement.


RATIO OF EARNINGS TO FIXED CHARGES

 
  Nine Months
Ended
September 30,
2007

  Year Ended December 31,
(Unaudited)

  2006
  2005
  2004
  2003
  2002
Ratio of Earnings to Fixed Charges   2.3   2.2   2.1   2.2   2.2   2.5

        For purposes of computing the ratio of earnings to fixed charges, (1) earnings consist of income from continuing operations plus fixed charges, federal and state income taxes, deferred income taxes and investment tax credits and less undistributed equity in earnings of unconsolidated affiliates; and (2) fixed charges consist of interest on long-term debt, other interest charges, the interest component on leases and amortization of debt discount, premium and expense plus distributions on redeemable preferred securities of subsidiary trust.

1



DESCRIPTION OF SENIOR UNSECURED DEBT SECURITIES

        The description below contains summaries of selected provisions of the indenture, including supplemental indentures, under which the unsecured senior debt securities will be issued. These summaries are not complete. The indenture and the form of the supplemental indenture applicable to the senior debt securities have been filed as exhibits to the registration statement. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

        We are not required to issue future issues of indebtedness under the indenture described in this prospectus. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not under this registration statement.

        The senior debt securities will be represented either by global senior debt securities registered in the name of The Depository Trust Company ("DTC"), as depository ("Depository"), or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the heading "Book-Entry System" in this prospectus.

General

        The senior debt securities will be issued in one or more new series under an indenture dated as of December 1, 2000 between us and Wells Fargo Bank, National Association, as trustee (the "Senior Debt Trustee"). This indenture, as previously supplemented by supplemental indentures and as to be supplemented by a new supplemental indenture for each series of debt securities, is referred to in this prospectus as the "Senior Indenture." As of September 30, 2007, there were four series of senior debt securities in an aggregate principal amount of $1.108 billion outstanding under the Senior Indenture.

        The holders of the outstanding senior debt securities do not, and, unless the supplemental indenture that describes a particular series of senior debt securities provides otherwise with respect to that series, the holders of any senior debt securities offered by this prospectus will not, have the right to require us to repurchase the senior debt securities if we become involved in a highly leveraged or change in control transaction. The Senior Indenture does not have any provision that is designed specifically in response to highly leveraged or change in control transactions. However, any change in control transaction and any incurrence of substantial additional long-term indebtedness, as senior debt securities or otherwise, by us in such a transaction of that nature would require approval of state utility regulatory authorities and, possibly, of federal regulatory authorities.

        The senior debt securities will be our unsecured and unsubordinated obligations. The senior debt securities will rank on a parity in right of payment with all of our existing and future unsecured and unsubordinated indebtedness. There are currently no outstanding debt obligations junior to the senior debt securities. However, the senior debt securities will be subordinated to any of our secured indebtedness, as to the assets securing such indebtedness. As of September 30, 2007, we had no secured indebtedness and our unsecured and unsubordinated indebtedness was approximately $1.416 billion.

        In addition, the senior debt securities will be effectively subordinated to all existing and future liabilities of our subsidiaries. We are a holding company and conduct business through our various subsidiaries. As a result, our cash flow and consequent ability to meet our debt obligations primarily depend on the earnings of our subsidiaries, and on dividends and other payments from our subsidiaries. Under certain circumstances, contractual and legal restrictions, as well as the financial condition and operating requirements of our subsidiaries, could limit our ability to obtain cash from our subsidiaries for the purpose of meeting debt service obligations, including the payment of principal and interest on the senior debt securities. Any rights to receive assets of any subsidiary upon its liquidation or reorganization and the consequent right of the holders of the senior debt securities to participate in

2



those assets will be subject to the claims of that subsidiary's creditors, including trade creditors, except to the extent that we are recognized as a creditor of that subsidiary, in which case our claims would still be subordinate to any security interests in the assets of that subsidiary. As of September 30, 2007, our subsidiaries had approximately $14.802 billion of indebtedness and other liabilities outstanding.

        In this "Description of Senior Unsecured Debt Securities" we refer to securities issued under the Senior Indenture, whether previously issued or to be issued in the future, including the senior debt securities, as the "securities." The amount of securities that we may issue under the Senior Indenture is not limited. We are not required to issue all senior debt securities of one series at the same time and, unless we indicate otherwise in the applicable prospectus supplement, we may reopen a series for issuances of additional senior debt securities of that series without the consent of the holders of the senior debt securities of that series.

        When we offer to sell a particular series of senior debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:


        Any special U.S. federal income tax considerations applicable to senior debt securities sold at an original issue discount and any special U.S. federal income tax or other considerations applicable to any senior debt securities which are denominated in currencies other than U.S. dollars will be described in the prospectus supplement relating to that series of senior debt securities.

        Unless we indicate otherwise in the applicable prospectus supplement, the senior debt securities will be denominated in U.S. dollars in minimum denominations of $1,000 and integral multiples thereof, except that the denomination of any senior debt security issued in the form of a global debt security will not exceed $400,000,000 without the approval of the Depository.

Registration, Transfer and Exchange

        Senior debt securities of any series may be exchanged for other senior debt securities of the same series of any authorized denominations and of a like aggregate principal amount, series and stated maturity and having the same terms and original issue date or dates. (Section 2.6 of the Senior Indenture).

        Unless we indicate otherwise in the applicable prospectus supplement, senior debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer), at the office of the Senior Debt Trustee maintained for that purpose with respect to any series of senior debt securities and referred to in the applicable prospectus supplement,

3



without service charge and upon payment of any taxes and other governmental charges as described in the Senior Indenture. Any transfer or exchange will be effected if the senior debt securities are duly endorsed by, or accompanied by a written instrument or instruments of transfer in a form satisfactory to the Company and the Senior Debt Trustee and duly executed by the holder of the senior debt security as described in the Senior Indenture. (Section 2.6 of the Senior Indenture).

        The Senior Debt Trustee will not be required to exchange or register a transfer of any senior debt securities of a series selected, called or being called for redemption except, in the case of any senior debt security to be redeemed in part, the portion thereof not to be so redeemed. (Section 2.6 of the Senior Indenture). See the information under the heading "Book-Entry System."

Payment and Paying Agents

        Principal, interest and premium, if any, on senior debt securities issued in the form of global senior debt securities will be paid in the manner described below under the heading "Book-Entry System." Unless we indicate otherwise in the applicable prospectus supplement, interest on senior debt securities that are in the form of certificated senior debt securities will be paid by check mailed to the holder at that person's address as it appears in the register for the senior debt securities maintained by the Senior Debt Trustee; however, a holder of $10,000,000 or more senior debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer to a bank within the continental United States if appropriate wire transfer instructions have been received by the Senior Debt Trustee on or prior to the applicable record date. (Section 2.12 of the Senior Indenture). Unless we indicate otherwise in the applicable prospectus supplement, the principal, interest at maturity and premium, if any, on senior debt securities in the form of certificated senior debt securities will be payable in immediately available funds at the office of the Senior Debt Trustee. (Section 2.12 of the Senior Indenture).

        All monies paid by us to a paying agent for the payment of principal, interest or premium, if any, on any senior debt security which remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us and the holder of that senior debt security will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Senior Indenture).

Events of Default and Remedies

        The following constitute events of default under the Senior Indenture:

(Section 7.1 of the Senior Indenture).

        Acceleration of Maturity.    If an event of default occurs and is continuing, either the Senior Debt Trustee or the holders of a majority in principal amount of the outstanding senior debt securities may declare the principal amount of all senior debt securities to be due and payable immediately. At any time after an acceleration of the securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of the securities has been obtained, if we pay or deposit

4



with the Senior Debt Trustee a sum sufficient to pay all matured installments of interest and the principal and any premium which has become due otherwise than by acceleration and all defaults have been cured or waived, then that payment or deposit will cause an automatic rescission and annulment of the acceleration of the securities. (Section 7.1 of the Senior Indenture).

        Indemnification of Senior Debt Trustee.    The Senior Debt Trustee generally will be under no obligation to exercise any of its rights or powers under the Senior Indenture at the request or direction of any of the holders unless such holders have offered reasonable security or indemnity to the Senior Debt Trustee. (Section 8.2 of the Senior Indenture).

        Right to Direct Proceedings.    The holders of a majority in principal amount of the outstanding securities generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Senior Debt Trustee, or of exercising any trust or power conferred on the Senior Debt Trustee, relating to the securities. However, the Senior Debt Trustee may refuse to follow any direction that conflicts with law or the Senior Indenture or would expose the Senior Debt Trustee to personal liability or be unduly prejudicial to holders not joining in such proceeding. (Section 7.7 of the Senior Indenture).

        Limitation on Rights to Institute Proceedings.    No holder of the senior debt securities of a series will have any right to pursue a remedy under the Senior Indenture, unless:

(Section 7.4 of the Senior Indenture).

        No Impairment of Right to Receive Payment.    Notwithstanding any other provision of the Senior Indenture, the holder of any senior debt security will have the absolute and unconditional right to receive payment of the principal, premium, if any, and interest on that senior debt security when due, and to institute suit for enforcement of that payment. This right may not be impaired without the consent of the holder. (Section 7.4 of the Senior Indenture).

        Notice of Default.    The Senior Debt Trustee is required to give the holders notice of the occurrence of a default within 90 days of the default, unless the default is cured or waived. Except in the case of a payment default on the senior debt securities, or a default in the payment of any sinking or purchase fund installments, the Senior Debt Trustee may withhold the notice if its board of directors or trustees, executive committee, or a trust committee of directors or trustees or responsible officers determines in good faith that it is in the interest of holders to do so. (Section 7.8 of the Senior Indenture). We are required to deliver to the Senior Debt Trustee each year a certificate as to whether or not we are in compliance with the conditions and covenants under the Senior Indenture. (Section 5.5 of the Senior Indenture).

Modification

        Unless we indicated otherwise in the applicable prospectus supplement, we and the Senior Debt Trustee may modify and amend the Senior Indenture from time to time.

5



        We will not need the consent of the holders for the following types of amendments:

(Section 12.1 of the Senior Indenture).

        We will need the consent of the holders of each outstanding security affected by a proposed amendment if the amendment would cause any of the following to occur:

6


(Section 12.2 of the Senior Indenture).

        Amendments other than those described in the above two paragraphs will require the approval of a majority in principal amount of the outstanding securities.

Defeasance and Discharge

        We may be discharged from all obligations relating to the senior debt securities and the Senior Indenture (except for specified obligations such as obligations to register the transfer or exchange of securities, replace stolen, lost or mutilated securities and maintain paying agencies) if we irrevocably deposit with the Senior Debt Trustee, in trust for the benefit of holders of securities, money or U.S. government obligations (or any combination thereof) sufficient to make all payments of principal, premium and interest on the securities on the dates those payments are due. To discharge these obligations, we must deliver to the Senior Debt Trustee an opinion of counsel that the holders of the securities will not recognize income, gain or loss for federal income tax purposes as a result of such defeasance or discharge of the Senior Indenture. Upon any discharge of our obligations as described above, we will be deemed to have paid and discharged our entire indebtedness represented by the senior debt securities and our obligations under the senior debt securities. (Section 4.1 of the Senior Indenture).

Consolidation, Merger and Sale of Assets; No Financial Covenants

        We will not consolidate with or merge into any other corporation or sell, or otherwise dispose all or substantially all of our assets unless the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium on all the securities and our obligation to perform every covenant of the Senior Indenture that we are to perform or observe, and we or the successor or transferee corporation, as applicable, are not immediately following such consolidation or merger, or sale, or disposition in default in the performance of any such covenant. Upon any consolidation or merger, or any sale, transfer or other disposition of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Senior Indenture with the same effect as if the successor corporation had been named as us in the Senior Indenture and we will be released from all obligations under the Senior Indenture. Regardless of whether a sale or transfer of assets might otherwise be considered a sale of all or substantially all of our assets, the Senior Indenture also specifically permits any sale, transfer or conveyance of our non-utility subsidiaries if, following such sale or transfer, the securities are rated by Standard & Poor's Ratings Group and Moody's Investors Service, Inc. at least as high as the ratings accorded the securities immediately prior to the sale, transfer or disposition. (Sections 11.1 and 11.2 of the Senior Indenture).

        The Senior Indenture does not contain any financial or other similar restrictive covenants.

Resignation or Removal of Senior Debt Trustee

        The Senior Debt Trustee may resign at any time by notifying us in writing and specifying the day that the resignation is to take effect. The resignation will not take effect, however, until the later of the appointment of a successor trustee and the day the resignation is to take effect. (Section 8.10 of the Senior Indenture).

        The holders of a majority in principal amount of the outstanding securities may remove the Senior Debt Trustee at any time. In addition, so long as no event of default or event which, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing, we

7



may remove the Senior Debt Trustee upon notice to the holder of each security outstanding and written notice to the Senior Debt Trustee. (Section 8.10 of the Senior Indenture).

Governing Law

        The Senior Indenture and the senior debt securities will be governed by, and will be construed in accordance with, the laws of the State of Minnesota.

Concerning the Senior Debt Trustee

        Wells Fargo Bank, National Association is the Senior Debt Trustee. We maintain banking relationships with the Senior Debt Trustee in the ordinary course of business. The Senior Debt Trustee also acts as trustee for our junior subordinated debt securities and certain debt securities of our subsidiaries.

8



DESCRIPTION OF JUNIOR SUBORDINATED DEBT SECURITIES

        The description below contains summaries of selected provisions of the indenture, including supplemental indentures, under which the unsecured junior subordinated debt securities will be issued. These summaries are not complete. The indenture and the form of the supplemental indenture applicable to the junior subordinated debt securities have been filed as exhibits to the registration statement. You should read them for provisions that may be important to you. In the summaries below, we have included references to section numbers of the indenture so that you can easily locate these provisions.

        We are not required to issue future issues of indebtedness under the indenture described in this prospectus. We are free to use other indentures or documentation, containing provisions different from those described in this prospectus, in connection with future issues of other indebtedness not under this registration statement.

        The junior subordinated debt securities will be represented either by global junior subordinated debt securities registered in the name of the Depository or its nominee, or by securities in certificated form issued to the registered owners, as set forth in the applicable prospectus supplement. See the information under the heading "Book-Entry System" in this prospectus.

General

        The junior subordinated debt securities will be issued in one or more new series under a junior subordinated indenture to be entered into between us and Wells Fargo Bank, National Association, as trustee (the "Subordinated Debt Trustee"). This indenture, as it may be supplemented by a supplemental indenture for each series of junior subordinated debt securities, is referred to in this prospectus as the "Subordinated Indenture."

        The junior subordinated debt securities will be our unsecured obligations and will rank junior in right of payment to our Senior Indebtedness, as described under the caption "—Subordination." As of September 30, 2007, we have no secured indebtedness and our unsecured and unsubordinated indebtedness was approximately $1.416 billion.

        In addition, the junior subordinated debt securities will be effectively subordinated to all existing and future liabilities of our subsidiaries, including trade creditors, debtholders, secured creditors, taxing authorities, guarantee holders and any preferred stockholders. We are a holding company and conduct business through our various subsidiaries. As a result, our cash flow and consequent ability to meet our debt obligations primarily depend on the earnings of our subsidiaries, and on dividends and other payments from our subsidiaries. Under certain circumstances, contractual and legal restrictions, as well as the financial condition and operating requirements of our subsidiaries, could limit our ability to obtain cash from our subsidiaries for the purpose of meeting debt service obligations, including the payment of principal and interest on the junior subordinated debt securities. Any rights to receive assets of any subsidiary upon its liquidation or reorganization and the consequent right of the holders of the junior subordinated debt securities to participate in those assets will be subject to the claims of that subsidiary's creditors, including trade creditors, except to the extent that we are recognized as a creditor of that subsidiary, in which case our claims would still be subordinate to any security interests in the assets of that subsidiary. As of September 30, 2007, our subsidiaries had approximately $14.802 billion of indebtedness and other liabilities outstanding.

        Unless the supplemental indenture that describes a particular series of junior subordinated debt securities provides otherwise with respect to that series, the holders of any junior subordinated debt securities offered by this prospectus will not have the right to require us to repurchase the junior subordinated debt securities if we become involved in a highly leveraged or change in control transaction. The Subordinated Indenture does not have any provision that is designed specifically in

9



response to highly leveraged or change in control transactions. However, any change in control transaction and any incurrence of substantial additional long-term indebtedness, as junior subordinated debt securities or otherwise, by us in such a transaction of that nature would require approval of state utility regulatory authorities and, possibly, of federal regulatory authorities.

        In this "Description of Junior Subordinated Debt Securities" we refer to securities issued under the Subordinated Indenture as the "securities." The amount of securities that we may issue under the Subordinated Indenture is not limited. We are not required to issue all junior subordinated debt securities of one series at the same time and, unless we indicate otherwise in the applicable prospectus supplement, we may reopen a series for issuances of additional junior subordinated debt securities of that series without the consent of the holders of the junior subordinated debt securities of that series.

        When we offer to sell a particular series of junior subordinated debt securities, we will describe the specific terms of that series in a prospectus supplement relating to that series, including the following terms:

        Any special U.S. federal income tax considerations applicable to junior subordinated debt securities sold at an original issue discount and any special U.S. federal income tax or other considerations applicable to any junior subordinated debt securities which are denominated in currencies other than U.S. dollars will be described in the prospectus supplement relating to that series of junior subordinated debt securities.

        Unless we indicate otherwise in the applicable prospectus supplement, the junior subordinated debt securities will be denominated in U.S. dollars in minimum denominations of $1,000 and integral multiples thereof.

10



Subordination

        Each series of junior subordinated debt securities will be subordinate and junior in right of payment, to the extent set forth in the Subordinated Indenture, to all Senior Indebtedness (as defined below). If:


then the holders of Senior Indebtedness generally will have the right to receive payment, in the case of the first instance above, of all amounts due or to become due upon that Senior Indebtedness, and, in the case of the second and third instances, of all amounts due on that Senior Indebtedness, or we will make provision for those payments, before the holders of any junior subordinated debt securities have the right to receive any payments of principal or interest on their securities. (Sections 14.1 and 14.9 of the Subordinated Indenture).

        "Senior Indebtedness" means, with respect to any series of junior subordinated debt securities, the principal, premium, interest and any other payment in respect of any of the following (whether outstanding on the date of execution of the Subordinated Indenture or thereafter incurred):

        Senior Indebtedness will not include trade accounts payable, accrued liabilities arising in the ordinary course of business, indebtedness to our subsidiaries or any indebtedness which is by its terms junior to or on parity with the junior subordinated debt securities. (Section 1.1 of the Subordinated Indenture).

        Senior Indebtedness will be entitled to the benefits of the subordination provisions in the Subordinated Indenture irrespective of the amendment, modification or waiver of any term of the Senior Indebtedness. We may not amend the Subordinated Indenture to change the subordination of any outstanding Senior Indebtedness without the consent of each holder of Senior Indebtedness that such amendment would adversely affect. (Sections 12.2 and 14.7 of the Subordinated Indenture).

        The Subordinated Indenture does not limit the amount of Senior Indebtedness that we may issue.

11



Registration, Transfer and Exchange

        Junior subordinated debt securities of any series may be exchanged for other junior subordinated debt securities of the same series of any authorized denominations and of a like aggregate principal amount, series and stated maturity and having the same terms and original issue date or dates. (Section 2.6 of the Subordinated Indenture).

        Unless we indicate otherwise in the applicable prospectus supplement, junior subordinated debt securities may be presented for registration of transfer (duly endorsed or accompanied by a duly executed written instrument of transfer), at the office of the Subordinated Debt Trustee maintained for that purpose with respect to any series of junior subordinated debt securities and referred to in the applicable prospectus supplement, without service charge and upon payment of any taxes and other governmental charges as described in the Subordinated Indenture. Any transfer or exchange will be effected if the junior subordinated debt securities are duly endorsed by, or accompanied by a written instrument or instruments of transfer in a form satisfactory to the Company and the Subordinated Debt Trustee and duly executed by the holder of the junior subordinated debt security as described in the Subordinated Indenture. (Section 2.6 of the Subordinated Indenture).

        The Subordinated Debt Trustee will not be required to exchange or register a transfer of any junior subordinated debt securities of a series selected, called or being called for redemption except, in the case of any junior subordinated debt security to be redeemed in part, the portion thereof not to be so redeemed. (Section 2.6 of the Subordinated Indenture). See the information under the heading "Book-Entry System."

Payment and Paying Agents

        Principal, interest and premium, if any, on junior subordinated debt securities issued in the form of global junior subordinated debt securities will be paid in the manner described below under the heading "Book-Entry System." Unless we indicate otherwise in the applicable prospectus supplement, interest on junior subordinated debt securities that are in the form of certificated junior subordinated debt securities will be paid by check mailed to the holder at that person's address as it appears in the register for the junior subordinated debt securities maintained by the Subordinated Debt Trustee; however, a holder of $10,000,000 or more junior subordinated debt securities having the same interest payment dates will be entitled to receive payments of interest by wire transfer to a bank within the continental United States if appropriate wire transfer instructions have been received by the Subordinated Debt Trustee on or prior to the applicable record date. (Section 2.12 of the Subordinated Indenture). Unless we indicate otherwise in the applicable prospectus supplement, the principal, interest at maturity and premium, if any, on junior subordinated debt securities in the form of certificated junior subordinated debt securities will be payable in immediately available funds at the office of the Subordinated Debt Trustee. (Section 2.12 of the Subordinated Indenture).

        All monies paid by us to a paying agent for the payment of principal, interest or premium, if any, on any junior subordinated debt security which remain unclaimed at the end of two years after that principal, interest or premium has become due and payable will be repaid to us and the holder of that junior subordinated debt security will thereafter look only to us for payment of that principal, interest or premium. (Section 4.4 of the Subordinated Indenture).

12



Events of Default and Remedies

        Unless we provide otherwise in a prospectus supplement, the following will constitute events of default under the Subordinated Indenture with respect to the junior subordinated debt securities of any series:

(Section 7.1 of the Subordinated Indenture).

        Acceleration of Maturity.    If an event of default occurs and is continuing with respect to a series of junior subordinated debt securities, either the Subordinated Debt Trustee or the holders of at least 25% in principal amount of the outstanding securities of that series may declare the principal amount of all securities of that series to be due and payable immediately. At any time after an acceleration of a series of securities has been declared, but before a judgment or decree of the immediate payment of the principal amount of those securities has been obtained, if:

then that holders' rescission and the payment or deposit will cause an automatic rescission and annulment of the acceleration of the securities of that series. (Section 7.1 of the Subordinated Indenture).

        Indemnification of Subordinated Debt Trustee.    The Subordinated Debt Trustee generally will be under no obligation to exercise any of its rights or powers under the Subordinated Indenture at the request or direction of any of the holders unless such holders have offered reasonable security or indemnity to the Subordinated Debt Trustee. (Section 8.2 of the Subordinated Indenture).

        Right to Direct Proceedings.    The holders of a majority in principal amount of the outstanding securities of a series generally will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the Subordinated Debt Trustee, or of exercising any trust or power conferred on the Subordinated Debt Trustee, relating to the securities of that series. Notwithstanding, the Subordinated Debt Trustee may refuse to follow any direction that conflicts with law or the Subordinated Indenture or would expose the Subordinated Debt Trustee to personal liability or be unduly prejudicial to holders not joining in such proceeding. (Section 7.7 of the Subordinated Indenture).

13


        Limitation on Rights to Institute Proceedings.    No holder of the junior subordinated debt securities of a series will have any right to pursue a remedy under the Subordinated Indenture, unless:

(Section 7.4 of the Subordinated Indenture).

        No Impairment of Right to Receive Payment.    Notwithstanding any other provision of the Subordinated Indenture, the holder of any junior subordinated debt security will have the absolute and unconditional right to receive payment of the principal, premium, if any, and interest on that junior subordinated debt security when due and payable, and to institute suit for enforcement of that payment. This right may not be impaired without the consent of the holder. (Section 7.4 of the Subordinated Indenture).

        Notice of Default.    The Subordinated Debt Trustee is required to give the holders of a series of securities notice of the occurrence of a default within 90 days of the default with respect to that series, unless the default is cured or waived. Except in the case of a payment default on the junior subordinated debt securities, or a default in the payment of any sinking or purchase fund installments, the Subordinated Debt Trustee may withhold the notice if its board of directors or trustees, executive committee, or a trust committee of directors or trustees or responsible officers determines in good faith that it is in the interest of holders of the series of affected securities to do so. (Section 7.8 of the Subordinated Indenture). We are required to deliver to the Subordinated Debt Trustee each year a certificate as to whether or not we are in compliance with the conditions and covenants under the Subordinated Indenture. (Section 5.5 of the Subordinated Indenture).

Defeasance and Discharge

        We may be discharged from all obligations relating to the junior subordinated debt securities and the Subordinated Indenture (except for specified obligations such as obligations to register the transfer or exchange of securities, replace stolen, lost or mutilated securities and maintain paying agencies) if we irrevocably deposit with the Subordinated Debt Trustee, in trust for the benefit of holders of securities, money or U.S. government obligations (or any combination thereof) sufficient to make all payments of principal, premium and interest on the securities on the dates those payments are due. To discharge these obligations, we must deliver to the Subordinated Debt Trustee an opinion of counsel to the effect that we have received from, or there has been published by, the Internal Revenue Service a ruling or similar pronouncement by the Internal Revenue Service or that there has been a change in law, in either case to the effect that the holders of the securities will not recognize income, gain or loss for federal income tax purposes as a result of such defeasance or discharge of the Subordinated Indenture, and holders will be subject to tax in the same manner, in the same amounts and and same time as would have been the case absent such defeasance. Upon any discharge of our obligations as described above, we will be deemed to have paid and discharged our entire indebtedness represented by the junior subordinated debt securities and our obligations under the junior subordinated debt securities. (Section 4.1 of the Subordinated Indenture).

14



Modification

        Unless we indicate otherwise in the applicable prospectus supplement, we and the Subordinated Debt Trustee may modify and amend the Subordinated Indenture from time to time.

        We will not need the consent of the holders for the following types of amendments:

(Section 12.1 of the Subordinated Indenture).

        We will need the consent of the holders of each outstanding security affected by a proposed amendment if the amendment would cause any of the following to occur:

15


(Section 12.2 of the Subordinated Indenture).

        Amendments other than those described in the above two paragraphs will require the approval of a majority in principal amount of the outstanding securities of all series, provided that if there are securities of more than one series outstanding and if a proposed amendment would directly affect the rights of holders of securities of one or more, but less than all, of such series, then the approval of a majority in principal amount of the outstanding securities of all series so directly affected, considered as one class, will be required.

Consolidation, Merger and Sale of Assets; No Financial Covenants

        We will not consolidate with or merge into any other corporation or sell, or otherwise dispose all or substantially all of our assets unless the successor or transferee corporation assumes by supplemental indenture our obligations to pay the principal, interest and premium on all the securities and our obligation to perform every covenant of the Subordinated Indenture that we are to perform or observe, and we or the successor or transferee corporation, as applicable, are not immediately following such consolidation or merger, or sale, or disposition in default in the performance of any such covenant. Upon any consolidation or merger, or any sale, transfer or other disposition of all or substantially all of our assets, the successor or transferee corporation will succeed to, and be substituted for, and may exercise all of our rights and powers under the Subordinated Indenture with the same effect as if the successor corporation had been named as us in the Subordinated Indenture and we will be released from all obligations under the Subordinated Indenture. Regardless of whether a sale or transfer of assets might otherwise be considered a sale of all or substantially all of our assets, the Subordinated Indenture also specifically permits any sale, transfer or conveyance of our non-utility subsidiaries if, following such sale or transfer, the securities are rated by Standard & Poor's Ratings Group and Moody's Investors Service, Inc. at least as high as the ratings accorded the securities immediately prior to the sale, transfer or disposition. (Sections 11.1 and 11.2 of the Subordinated Indenture).

        The Subordinated Indenture does not contain any financial or other similar restrictive covenants.

Resignation or Removal of Subordinated Debt Trustee

        The Subordinated Debt Trustee may resign with respect to securities of any series at any time by notifying us in writing and specifying the day that the resignation is to take effect. The resignation will not take effect, however, until the later of the appointment of a successor trustee and the day the resignation is to take effect. (Section 8.10 of the Subordinated Indenture).

        The holders of a majority in principal amount of the outstanding securities of any series may remove the Subordinated Debt Trustee as trustee of that series of securities at any time. In addition, so long as no event of default or event which, with the giving of notice or lapse of time or both, would become an event of default has occurred and is continuing with respect to securities of any series, we may remove the Subordinated Debt Trustee with respect to securities of that series upon notice to the holder of each security of that series outstanding and written notice to the Subordinated Debt Trustee. (Section 8.10 of the Subordinated Indenture).

16



Governing Law

        The Subordinated Indenture and the junior subordinated debt securities will be governed by, and will be construed in accordance with, the laws of the State of Minnesota. (Section 15.4 of the Subordinated Indenture).

Concerning the Subordinated Debt Trustee

        Wells Fargo Bank, National Association is the Subordinated Debt Trustee. We maintain banking relationships with the Subordinated Debt Trustee in the ordinary course of business. The Subordinated Debt Trustee also acts as trustee for our senior debt securities and certain debt securities of our subsidiaries.


BOOK-ENTRY SYSTEM

        Each series of senior debt securities or junior subordinated debt securities, collectively referred to in this section as "debt securities," offered by this prospectus may be issued in the form of one or more global debt securities representing all or part of that series of debt securities. This means that we will not issue certificates for that series of debt securities to the holders. Instead, a global debt security representing that series will be deposited with, or on behalf of, DTC, or its successor as the Depository and registered in the name of the Depository or a nominee of the Depository.

        The Depository will keep a computerized record of its participants (for example, your broker) whose clients have purchased securities represented by a global debt security. Unless it is exchanged in whole or in part for a certificated debt security, a global debt security may not be transferred, except that the Depository, its nominees and their successors may transfer a global debt security as a whole to one another.

        Beneficial interests in global debt securities will be shown on, and transfers of interests will be made only through, records maintained by the Depository and its participants. The laws of some jurisdictions require that some purchasers take physical delivery of securities in definitive form. These laws may impair the ability to transfer beneficial interests in a global debt security.

        We will wire principal, interest and any premium payments to the Depository or its nominee. We and the applicable Trustee will treat the Depository or its nominee as the owner of the global debt security for all purposes, including any notices and voting. Accordingly, we, the applicable Trustee and any paying agent will have no direct responsibility or liability to pay amounts due on a global debt security to owners of beneficial interests in a global debt security.

        Unless we specify otherwise in the applicable prospectus supplement, DTC will act as Depository for debt securities issued as global debt securities. The debt securities will be registered in the name of Cede & Co. (DTC's partnership nominee).

        DTC is a limited-purpose trust company organized under the New York Banking Law, a "banking organization" within the meaning of the New York Banking Law, a member of the Federal Reserve System, a "clearing corporation" within the meaning of the New York Uniform Commercial Code, and a "clearing agency" registered pursuant to the provisions of Section 17A of the Securities Exchange Act of 1934. DTC holds securities that its participants ("Direct Participants") deposit with DTC. DTC also facilitates the post-trade settlement among Direct Participants of sales and other securities transactions in deposited securities through electronic computerized book-entry transfers and pledges between Direct Participants' accounts. This eliminates the need for physical movement of securities certificates. Direct Participants include both U.S. and non-U.S. securities brokers and dealers, banks, trust companies, clearing corporations, and certain other organizations. DTC is a wholly-owned subsidiary of The Depository Trust & Clearing Corporation ("DTCC"). DTCC, in turn is owned by a number of Direct Participants of DTC and Members of the National Securities Clearing Corporation, Government

17


Securities Clearing Corporation, MBS Clearing Corporation and Emerging Markets Clearing Corporation (NSCC, GSCC, MBSCC and EMCC, are also subsidiaries of DTCC), as well as by the New York Stock Exchange, Inc., the American Stock Exchange, LLC, and the National Association of Securities Dealers, Inc. Access to the DTC system is also available to others such as securities brokers and dealers, banks, trust companies and clearing corporations that clear through or maintain a custodial relationship with a Direct Participant, either directly or indirectly ("Indirect Participants"). The rules that apply to DTC and its Direct or Indirect Participants (collectively, "Participants") are on file with the SEC. More information about DTC can be found at www.dtcc.com.

        Purchases of debt securities under the DTC system must be made by or through Direct Participants, which will receive a credit for the debt securities on DTC's records. The ownership interest of each actual purchaser of each debt security ("Beneficial Owner") is in turn to be recorded on the Direct and Indirect Participants' records. Beneficial Owners will not receive written confirmation from DTC of their purchase. Beneficial Owners are, however, expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the Direct or Indirect Participant through which the Beneficial Owner entered into the transaction. Transfers of ownership interests in the debt securities are to be accomplished by entries made on the books of Direct and Indirect Participants acting on behalf of Beneficial Owners. Beneficial Owners will not receive certificates representing their ownership interests in debt securities, except in the event that use of the book-entry system for the debt securities is discontinued.

        To facilitate subsequent transfers, all securities deposited by Direct Participants with DTC are registered in the name of DTC's partnership nominee, Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual Beneficial Owners of the debt securities; DTC's records reflect only the identity of the Direct Participants to whose accounts such debt securities are credited, which may or may not be the Beneficial Owners. The Direct and Indirect Participants will remain responsible for keeping account of their holdings on behalf of their customers.

        Conveyance of notices and other communications by DTC to Direct Participants, by Direct Participants to Indirect Participants, and by Direct Participants and Indirect Participants to Beneficial Owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

        Redemption notices shall be sent to DTC. If less than all of the debt securities within a series are being redeemed, DTC's practice is to determine by lot the amount of the interest of each Direct Participant in such series to be redeemed.

        Neither DTC nor Cede & Co. (nor such other DTC nominee) will consent or vote with respect to the debt securities unless authorized by a Direct Participant in accordance with DTC's procedures. Under its usual procedures, DTC mails an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns Cede & Co.'s consenting or voting rights to those Direct Participants to whose accounts the debt securities are credited on the record date (identified in a listing attached to the omnibus proxy).

        Redemption proceeds, distributions, and dividend payments on the debt securities will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC's practice is to credit Direct Participants' accounts, upon DTC's receipt of funds and corresponding detail information from us or the applicable Trustee on payable date in accordance with their respective holdings shown on DTC's records. Payments by Participants to Beneficial Owners will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in "street name," and will be the responsibility of such Participant and not of DTC nor its nominee, the applicable Trustee, or us, subject to any statutory

18



or regulatory requirements as may be in effect from time to time. Payment of redemption proceeds, distributions, and dividend payments to Cede & Co. (or such other nominee as may be requested by an authorized representative of DTC) is the responsibility of us or the applicable Trustee, disbursement of such payments to Direct Participants will be the responsibility of DTC, and disbursement of such payments to the Beneficial Owners will be the responsibility of Direct and Indirect Participants.

        DTC may discontinue providing its services as securities depository with respect to the debt securities at any time by giving reasonable notice to us or the applicable Trustee. Under such circumstances, in the event that a successor securities depository is not obtained, debt security certificates are required to be printed and delivered.

        We may decide to discontinue use of the system of book-entry-only transfers through DTC (or a successor securities depository). In that event, debt security certificates will be printed and delivered to DTC.

        The information in this section concerning DTC and DTC's book-entry system has been obtained from DTC, and we and any underwriters, dealers or agents are not responsible for the performance by DTC of its obligations under the rules and procedures governing its operations or otherwise.

        Any underwriters, dealers or agents of any debt securities may be Direct Participants of DTC.

19



DESCRIPTION OF COMMON STOCK

        The following summary description sets forth some of the general terms and provisions of the common stock. Because this is a summary description, it does not contain all of the information that may be important to you. For a more detailed description of the common stock, you should refer to the provisions of our Restated Articles of Incorporation and Bylaws.

General

        Our capital stock consists of two classes: common stock, par value $2.50 per share (1,000,000,000 shares currently authorized of which 428,782,700 shares were outstanding as of December 31, 2007); and preferred stock, par value $100 per share (7,000,000 shares authorized, of which the following series were outstanding as of December 31, 2007: $3.60 Series—275,000 shares; $4.08 Series— 150,000 shares; $4.10 Series—175,000 shares; $4.11 Series—200,000 shares; $4.16 Series—99,800 shares; and $4.56 Series—150,000 shares. Our board of directors is authorized to provide for the issue from time to time of preferred stock in series and, as to each series, to fix the designation, dividend rates and times of payment, redemption price, and liquidation price or preference as to assets in voluntary liquidation. Cumulative dividends, redemption provisions and sinking fund requirements, to the extent that some or all of these features are or may be present when preferred stock is issued, could have an adverse effect on the availability of earnings for distribution to the holders of the common stock or for other corporate purposes.

Dividend Rights

        Before we can pay any dividends on our common stock, the holders of our preferred stock are entitled to receive their dividends at the respective rates provided for in the terms of the shares of their series. See "Management's Discussion and Analysis of Financial Conditions and Results of Operations—Common Stock Dividends" in our Current Report on Form 8-K/A filed on December 13, 2007 for a discussion of factors affecting our payment of dividends.

Limitations on Payment of Dividends on and Acquisitions of Common Stock

        So long as any shares of our preferred stock are outstanding, dividends (other than dividends payable in common stock), distributions or acquisitions of our common stock:

        As described above, under these provisions, dividend payments may be restricted if our capitalization ratio (on a holding company basis only, i.e., not on a consolidated basis) is less than 25%. For those purposes, the capitalization ratio is equal to the (i) common stock plus surplus divided by (ii) the sum of common stock plus surplus plus long-term debt. Based on this definition, our capitalization ratio at September 30, 2007 was 84.8%. Although we have preferred stock outstanding, the restrictions do not place any effective limit on our ability to pay dividends because the restrictions are only triggered when the capitalization ratio is less than 25% or will be reduced to less than 25%

20



through dividends (other than dividends payable in common stock), distributions or acquisitions of our common stock.

        Because we are a holding company and conduct all of our operations through our subsidiaries, our cash flow and ability to pay dividends will be dependent on the earnings and cash flows of our subsidiaries and the distribution or other payment of those earnings to us in the form of dividends, or in the form of repayments of loans or advances to us. Some of our subsidiaries may have restrictions on their ability to pay dividends including covenants under their borrowing arrangements and mortgage indentures, and possibly also restrictions imposed by their regulators.

Voting Rights

        The holders of shares of preferred stock of the $3.60 Series are entitled to three votes for each share held, and the holders of our common stock and of all of our other series of preferred stock are entitled to one vote for each share held on all matters submitted to a vote of our stockholders. If, however, dividends payable on any series of our preferred stock are in default in an amount equal to the amount payable during the immediately preceding twelve-month period, the holders of shares of preferred stock, voting as a class and without regard to series, are entitled to elect the smallest number of directors necessary to constitute a majority of our board of directors and the holders of shares of common stock, voting as a class, are entitled to elect our remaining directors.

        The affirmative vote or consent of the holders of various specified percentages of preferred stock is required to effect selected changes in our capital structure and other transactions that might affect their rights. Except to the extent required by law, holders of common stock do not vote as a class in case of any modification of their rights.

Change of Control

        Our Bylaws, our shareholder rights plan (discussed below) and the Minnesota Business Corporation Act, as amended (the "Minnesota BCA"), contain provisions that could discourage or make more difficult a change of control of our company. These provisions are designed to protect our shareholders against coercive, unfair or inadequate tender offers and other abusive takeover tactics and to encourage any person contemplating a business combination with us to negotiate with our board of directors for the fair and equitable treatment of all of our shareholders.

        Election of Directors.    In electing directors, shareholders may cumulate their votes in the manner provided in the Minnesota BCA. Cumulative voting rights may make it more difficult for a group owning a significant amount of our voting securities to effect a change in the majority of the board of directors than would be the case if cumulative voting did not exist.

        Bylaw Provisions.    Under our Bylaws, our shareholders must provide us advance notice of the introduction by them of business at annual or special meetings of our shareholders. For a shareholder to properly bring a proposal before an annual or special meeting, the shareholder must comply with the shareholder proposal requirements under the federal proxy rules or deliver a written notice to the Corporate Secretary not less than 45 days nor more than 90 days prior to the date on which we first mailed our proxy materials for the prior year's annual meeting. If, however, during the prior year we did not hold an annual meeting, or if the date of the meeting has changed more than 30 days from the date of the prior year's meeting, the notice must be delivered to us within a reasonable time before we mail our proxy materials for the current year. If we have provided less than 30 days' notice or prior public disclosure of the date by which the shareholder's notice must be given, the shareholders' notice must be delivered to us not later than ten days following the earlier of the day on which notice of the date by which such shareholder's notice is required was mailed and the day on which such public disclosure was made. The required notice from a shareholder must contain (i) a description of the proposed business and the reasons for conducting such business, (ii) the name and address of each

21



shareholder supporting the proposal as it appears on our books, (iii) the class and number of shares beneficially owned by each shareholder supporting the proposal, and (iv) a description of any financial or other interest of each shareholder in the proposal.

        Minnesota BCA.    Section 302A.671 of the Minnesota BCA applies to potential acquirers of 20% or more of our voting shares. Section 302A.671 provides in substance that shares acquired by such acquirer will not have any voting rights unless:

        Section 302A.673 of the Minnesota BCA generally prohibits public Minnesota corporations, including us, from engaging in any business combination with a person or entity owning 10% or more of our voting shares for a period of four years after the date of the transaction in which such person or entity became a 10% shareholder unless the business combination or the acquisition resulting in 10% ownership was approved by a committee of disinterested directors prior to the date such person or entity became a 10% shareholder. Section 302A.675 of the Minnesota BCA provides in substance that a person or entity making a takeover offer (an "offeror") for us is prohibited from acquiring any additional shares of our company within two years following the last purchase of shares pursuant to the offer with respect to that class unless (i) the acquisition is approved by a committee of disinterested directors before the purchase of any shares by the offeror pursuant to the offer or (ii) our shareholders are afforded, at the time of the acquisition, a reasonable opportunity to dispose of their shares to the offeror upon substantially equivalent terms as those provided in the earlier takeover offer.

Liquidation Rights

        In the event of liquidation, after the holders of all series of preferred stock have received $100 per share in the case of involuntary liquidation, and the then applicable redemption prices in the case of voluntary liquidation, plus in either case an amount equal to all accumulated and unpaid dividends, the holders of the common stock are entitled to the remaining assets.

Preemptive and Subscription Rights and Transfer Agent

        No holder of our capital stock has the preemptive right to purchase or subscribe for any additional shares of our capital stock.

        Our common stock is listed on the New York Stock Exchange. The Bank of New York is the Transfer Agent and Registrar for the common stock.

Stockholder Rights Plan

        The board of directors declared a dividend of one right (a "Right") for each outstanding share of common stock of our company held of record at the close of business on June 28, 2001. Shares of common stock issued after June 28, 2001 and prior to the Separation Time (as defined below) or issued at any time after June 28, 2001 pursuant to any options and convertible securities outstanding at the Separation Time will also have Rights attached to them.

        Trading and Distribution of the Rights.    The Rights were issued under a Stockholder Protection Rights Agreement (the "Rights Agreement"), between us and The Bank of New York, as successor Rights Agent (the "Rights Agent"). Each Right entitles its registered holder to purchase from or

22



exchange with us, after the Separation Time, one share of common stock, for a price of $95.00 (the "Exercise Price"), subject to adjustment. Until the Separation Time, the Rights will not trade separately, but instead will be represented by, and transferred with, the common stock certificates (or in the case of uncertificated common stock, by the registration of the associated share of common stock on our stock transfer books). Common stock certificates issued after June 28, 2001 and prior to the Separation Time will represent one Right for each share of common stock and will contain a legend incorporating by reference the terms of the Rights Agreement (as it may be amended from time to time). Common stock certificates outstanding on June 28, 2001 also will represent one Right for each share of common stock even though they do not have this legend. Uncertificated common stock issued after June 28, 2001, but prior to the Separation Time which has been registered on our stock transfer books will represent one Right for each share of common stock registered. Promptly following the Separation Time, separate certificates representing the Rights will be mailed to holders of record of common stock at the Separation Time.

        The Separation Time will be the close of business on the earlier to occur of (i) the tenth business day (or any later date our board of directors determines prior to the Separation Time that would otherwise have occurred) after the date on which any person commences a tender or exchange offer which, if completed, would result in the person becoming an Acquiring Person (as defined below), and (ii) the first date or any later date as our board of directors may determine (the "Flip-in Date") of public announcement by us expressly stating that any person has become an Acquiring Person (the date of the public announcement being the "Stock Acquisition Date"). If a tender or exchange offer referred to in clause (i) is cancelled, terminated or otherwise withdrawn prior to the Separation Time without the purchase of any shares of stock, the offer will be deemed never to have been made.

        Acquiring Persons.    An Acquiring Person is any person, or group of affiliated or associated persons, having Beneficial Ownership (as defined in the Rights Agreement) of 15% or more of the outstanding shares of common stock. However, the following will not be deemed Acquiring Persons:

        Exercisability and Expiration.    The Rights will not be exercisable until the business day following the Separation Time. The Rights will expire (the "Expiration Time") on the earliest to occur of:

23


        Adjustments.    The Exercise Price and the number of Rights outstanding are subject to adjustment from time to time to prevent dilution in the event of a common stock dividend on, or a subdivision or a combination into a smaller number of shares of, common stock, or the issuance or distribution of any securities or assets in respect of, in lieu of or in exchange for common stock.

        Flip-in and Flip-over.    If a Flip-in Date (as defined above) occurs prior to the Expiration Time, we will take any necessary action to ensure and provide, to the extent permitted by applicable law, that each Right (other than Rights Beneficially Owned by the Acquiring Person or any affiliate or associate of an Acquiring Person, which Rights will become void) will constitute the right to purchase from us, upon exercise in accordance with the terms of the Rights Agreement, that number of shares of our common stock having an aggregate Market Price (as defined in the Rights Agreement), on the Stock Acquisition Date that gave rise to the Flip-in Date, equal to twice the Exercise Price for an amount in cash equal to the then-current Exercise Price. For example, at an Exercise Price of $95 per Right, each Right not owned by an Acquiring Person (or by related parties) "flips-in" following a Flip-in Date so that it entitles its holder to purchase $190 worth of common stock for $95. Assuming that the common stock had a per share market value of $25 at the time, the holder of each valid Right would, therefore, be entitled to purchase 7.6 shares of common stock for $95.

        Prior to the Expiration Time, if an Acquiring Person controls our board of directors and we then enter into, consummate or permit to occur a transaction or series of transactions in which, directly or indirectly:

24


        Redemption.    Our board of directors may, at its option, at any time prior to the close of business on the Flip-in Date, redeem all (but not less than all) the then-outstanding Rights at a price of $0.01 per Right (the "Redemption Price"), as provided in the Rights Agreement. Immediately upon the action of the board of directors electing to redeem the Rights, without any further action and without any notice, the right to exercise the Rights will terminate and each Right will thereafter represent only the right to receive the Redemption Price in cash for each Right so held.

        Exchange Option.    In addition, the board of directors may, at its option, at any time after a Flip-in Date and prior to the time that an Acquiring Person becomes the Beneficial Owner of more than 50% of the outstanding shares of common stock, elect to exchange all (but not less than all) the then-outstanding Rights (other than Rights Beneficially Owned by the Acquiring Person or any affiliate or associate thereof, which Rights will become void) for shares of common stock at an exchange ratio of one share of common stock per Right, appropriately adjusted to reflect any stock split, stock dividend or similar transaction occurring after the date of the Separation Time (the "Exchange Ratio"). Immediately upon such action by the board of directors (the "Exchange Time"), the right to exercise the Rights will terminate and each Right will thereafter represent only the right to receive a number of shares of common stock equal to the Exchange Ratio.

        Amendments.    The terms of the Rights may be amended by the board of directors (i) prior to the Flip-in Date in any manner and (ii) on or after the Flip-in Date to cure any ambiguity, to correct or supplement any provision of the Rights Agreement which may be defective or inconsistent with any other provisions, or in any manner not adversely affecting the interests of the holders of the Rights generally.

        Other Provisions.    The holders of Rights will, solely by reason of their ownership of Rights, have no rights as stockholders of our company, including, without limitation, the right to vote or to receive dividends. The Rights will not prevent a takeover of our company. However, the Rights may cause substantial dilution to a person or group that acquires 15% or more of the common stock unless the Rights are first redeemed by the board of directors. Nevertheless, the Rights should not interfere with a transaction that is in our best interests and our stockholders because the Rights can be redeemed on or prior to the Flip-in Date, before the consummation of such transaction.


PLAN OF DISTRIBUTION

        We may sell the offered securities (a) through agents; (b) through underwriters or dealers; (c) directly to one or more purchasers; or (d) through a combination of any of these methods of sale. We will identify the specific plan of distribution, including any underwriters, dealers, agents or direct purchasers and their compensation in a prospectus supplement.


LEGAL OPINIONS

        Legal opinions relating to the securities being offered by this prospectus will be rendered by Michael C. Connelly, 414 Nicollet Mall, Minneapolis, Minnesota, and Jones Day, Chicago, Illinois. Certain legal matters relating to the securities will be passed upon by Simpson Thacher & Bartlett LLP, New York, New York for any underwriters, dealers or agents named in a prospectus supplement. Michael C. Connelly is our Vice President and General Counsel and is the beneficial owner of less than 1% of our common stock.


EXPERTS

        The consolidated financial statements, the related financial statement schedules and management's report on the effectiveness of internal control over financial reporting incorporated in this prospectus by reference from the Company's Current Report on Form 8-K/A filed on December 13, 2007 for the

25



year ended December 31, 2006 have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports (which reports (1) express an unqualified opinion on the financial statements and financial statement schedules and include explanatory paragraphs relating to the adoption of Statement of Financial Accounting Standards No. 158, "Employer's Accounting for Defined Benefit Pension and Other Postretirement Plans," and the effects of the restatement described in Note 2, (2) express an unqualified opinion on management's assessment regarding the effectiveness of internal control over financial reporting, and (3) express an unqualified opinion on the effectiveness of internal control over financial reporting) which are incorporated herein by reference, and have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

26



PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 16.    EXHIBITS.

Exhibit
Number

  Description of Document
*1.01   Form of Underwriting Agreement relating to senior debt securities
*1.02   Form of Underwriting Agreement relating to common stock
**1.03   Form of Underwriting Agreement relating to junior subordinated debt securities
3.01   Restated Articles of Incorporation of the Company. (Filed as Exhibit 4.01 to the Company's Form 8-K Report (File No. 001-3034) filed on August 21, 2000 and incorporated by reference herein).
3.02   Bylaws of the Company. (Filed as Exhibit 3.01 to the Company's Form 10-Q Report (File No. 001-03034) filed on August 4, 2004 and incorporated by reference herein).
4.01   Trust Indenture dated December 1, 2000 between the Company and Wells Fargo Bank, National Association, as Trustee. (Filed as Exhibit 4.01 to the Company's Form 8-K Report (File No. 001-03034) dated December 18, 2000 and incorporated by reference herein).
4.02   Supplemental Trust Indenture dated December 15, 2000 between the Company and Wells Fargo Bank, National Association, as Trustee. (Filed as Exhibit 4.02 to the Company's Form 8-K Report (File No. 001-03034) dated December 18, 2000 and incorporated by reference herein).
4.03   Supplemental Trust Indenture No. 2 dated June 15, 2003 between the Company and Wells Fargo Bank, National Association, as Trustee, supplementing Trust Indenture dated December 1, 2000. (Filed as Exhibit 4.01 to the Company's Form 10-Q Report (File No. 001-03034) dated August 15, 2003) and incorporated by reference herein).
*4.04   Form of Supplemental Indenture for each series of senior debt securities.
4.05   Stockholder Protection Rights Agreement dated as of December 13, 2000 between the Company and The Bank of New York, as Successor Rights Agent. (Filed as Exhibit 1 to the Company's Form 8-K Report (File No. 001-03034) dated January 4, 2001 and incorporated by reference herein).
**4.06   Form of Junior Subordinated Indenture, between the Company and Wells Fargo Bank, National Association, as Trustee.
**4.07   Form of Supplemental Indenture for each series of junior subordinated debt securities.
**5.01   Opinion of Michael C. Connelly as to the legality of the securities.
**12.01   Statement of computation of ratio of earnings to fixed charges.
**23.01   Consent of Deloitte & Touche LLP, Independent Registered Public Accounting Firm.
23.02   Consent of Michael C. Connelly (included in Exhibit 5.01).
**24.01   Power of Attorney.
**25.01   Form T-1 Statement of Eligibility of Wells Fargo Bank, National Association to act as Trustee under the Senior Indenture and the Subordinated Indenture.

*
Previously filed.

**
Filed herewith.

II-1



ITEM 17.    UNDERTAKINGS.

        The undersigned registrant hereby undertakes:

provided, however, that paragraphs (i), (ii) and (iii) do not apply if the registration statement is on Form S-3 and the information required to be included in a post-effective amendment by those paragraphs is contained in reports filed with or furnished to the Commission by the registrant pursuant to section 13 or section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in the registration statement, or is contained in a form of prospectus filed pursuant to Rule 424(b) that is part of the registration statement.

II-2


II-3


II-4



SIGNATURE

        Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant certifies that it has reasonable grounds to believe that it meets all the requirements of filing on Form S-3 and has duly caused this post-effective amendment to registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Minneapolis, and State of Minnesota, on the 7th day of January, 2008.

    XCEL ENERGY INC.
         
    By:   /s/  BENJAMIN G.S. FOWKE III      
Benjamin G.S. Fowke III
Vice President and Chief Financial Officer

        Pursuant to the requirements of the Securities Exchange Act of 1933, as amended, this registration statement has been signed below by the following persons in the capacities and on the dates indicated.

Signature
  Title
  Date

 

 

 

 

 
*
Richard C. Kelly
  Chairman of the Board, President, Chief Executive Officer and Director   January 7, 2008

*

Teresa S. Madden

 

Controller (Chief Accounting Officer)

 

January 7, 2008

/s/  
BENJAMIN G.S. FOWKE III      
Benjamin G.S. Fowke III

 

Chief Financial Officer

 

January 7, 2008

*

C. Coney Burgess

 

Director

 

January 7, 2008

*

Fredric W. Corrigan

 

Director

 

January 7, 2008

*

Richard K. Davis

 

Director

 

January 7, 2008

*

Roger R. Hemminghaus

 

Director

 

January 7, 2008

*

A. Barry Hirschfeld

 

Director

 

January 7, 2008
         

II-5



*

Douglas W. Leatherdale

 

Director

 

January 7, 2008

*

Albert F. Moreno

 

Director

 

January 7, 2008

*

Margaret R. Preska

 

Director

 

January 7, 2008

*

A. Patricia Sampson

 

Director

 

January 7, 2008

*

Richard H. Truly

 

Director

 

January 7, 2008

*

David A. Westerlund

 

Director

 

January 7, 2008

*

Timothy V. Wolf

 

Director

 

January 7, 2008

*By:

 

/s/  
BENJAMIN G.S. FOWKE III      
Benjamin G.S. Fowke III
(Attorney-in-Fact)
January 7, 2008

 

 

 

 

II-6



EXHIBIT INDEX

Exhibit
Number

  Description of Document
*1.01   Form of Underwriting Agreement relating to senior debt securities
*1.02   Form of Underwriting Agreement relating to common stock
**1.03   Form of Underwriting Agreement relating to junior subordinated debt securities
3.01   Restated Articles of Incorporation of the Company. (Filed as Exhibit 4.01 to the Company's Form 8-K Report (File No. 001-3034) filed on August 21, 2000 and incorporated by reference herein).
3.02   Bylaws of the Company. (Filed as Exhibit 3.01 to the Company's Form 10-Q Report (File No. 001-03034) filed on August 4, 2004 and incorporated by reference herein).
4.01   Trust Indenture dated December 1, 2000 between the Company and Wells Fargo Bank, National Association, as Trustee. (Filed as Exhibit 4.01 to the Company's Form 8-K Report (File No. 001-03034) dated December 18, 2000 and incorporated by reference herein).
4.02   Supplemental Trust Indenture dated December 15, 2000 between the Company and Wells Fargo Bank, National Association, as Trustee. (Filed as Exhibit 4.02 to the Company's Form 8-K Report (File No. 001-03034) dated December 18, 2000 and incorporated by reference herein).
4.03   Supplemental Trust Indenture No. 2 dated June 15, 2003 between the Company and Wells Fargo Bank, National Association, as Trustee, supplementing Trust Indenture dated December 1, 2000. (Filed as Exhibit 4.01 to the Company's Form 10-Q Report (File No. 001-03034) dated August 15, 2003) and incorporated by reference herein).
*4.04   Form of Supplemental Indenture for each series of senior debt securities.
4.05   Stockholder Protection Rights Agreement dated as of December 13, 2000 between the Company and The Bank of New York, as Successor Rights Agent. (Filed as Exhibit 1 to the Company's Form 8-K Report (File No. 001-03034) dated January 4, 2001 and incorporated by reference herein).
**4.06   Form of Junior Subordinated Indenture, between the Company and Wells Fargo Bank, National Association, as Trustee.
**4.07   Form of Supplemental Indenture for each series of junior subordinated debt securities.
**5.01   Opinion of Michael C. Connelly as to the legality of the securities.
**12.01   Statement of computation of ratio of earnings to fixed charges.
**23.01   Consent of Deloitte & Touche LLP, Independent Registered Public Accounting Firm.
23.02   Consent of Michael C. Connelly (included in Exhibit 5.01).
**24.01   Power of Attorney.
**25.01   Form T-1 Statement of Eligibility of Wells Fargo Bank, National Association to act as Trustee under the Senior Indenture and the Subordinated Indenture.

*
Previously filed.

**
Filed herewith.



QuickLinks

TABLE OF CONTENTS
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
WHERE YOU CAN FIND MORE INFORMATION
XCEL ENERGY INC.
USE OF PROCEEDS
RATIO OF EARNINGS TO FIXED CHARGES
DESCRIPTION OF SENIOR UNSECURED DEBT SECURITIES
DESCRIPTION OF JUNIOR SUBORDINATED DEBT SECURITIES
BOOK-ENTRY SYSTEM
DESCRIPTION OF COMMON STOCK
PLAN OF DISTRIBUTION
LEGAL OPINIONS
EXPERTS
PART II INFORMATION NOT REQUIRED IN PROSPECTUS
SIGNATURE
EXHIBIT INDEX