
<PAGE>

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM T-1

                            Statement of Eligibility
                      Under the Trust Indenture Act of 1939
                  of a Corporation Designated to Act as Trustee

                Check if an Application to Determine Eligibility
                of a Trustee Pursuant to Section 305(b)(2) ______

                          HARRIS TRUST AND SAVINGS BANK
                                (Name of Trustee)

        Illinois                                         36-1194448
(State of Incorporation)                    (I.R.S. Employer Identification No.)

                 111 West Monroe Street, Chicago, Illinois 60603
                    (Address of principal executive offices)

                 Carolyn Potter, Harris Trust and Savings Bank,
                311 West Monroe Street, Chicago, Illinois, 60606
                    312-461-2531 phone 312-461-3525 facsimile
           (Name, address and telephone number for agent for service)

                          NORTHERN STATES POWER COMPANY
                                (Name of obligor)

       Minnesota                                         41-0448030
(State of Incorporation)                    (I.R.S. Employer Identification No.)

                                414 Nicollet Mall
                          Minneapolis, Minnesota 55401
                    (Address of principal executive offices)

                     First Mortgage Bonds, Series due ______
                         (Title of indenture securities)


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1.   GENERAL INFORMATION. Furnish the following information as to the Trustee:

     (a)  Name and address of each examining or supervising authority to which
          it is subject.

               Commissioner of Banks and Trust Companies, State of Illinois,
               Springfield, Illinois; Chicago Clearing House Association, 164
               West Jackson Boulevard, Chicago, Illinois; Federal Deposit
               Insurance Corporation, Washington, D.C.; The Board of Governors
               of the Federal Reserve System, Washington, D.C.

     (b)  Whether it is authorized to exercise corporate trust powers.

               Harris Trust and Savings Bank is authorized to exercise corporate
               trust powers.

2.   AFFILIATIONS WITH OBLIGOR. If the Obligor is an affiliate of the Trustee,
     describe each such affiliation.

               The Obligor is not an affiliate of the Trustee.

3. thru 15.

               NO RESPONSE NECESSARY

16.  LIST OF EXHIBITS.

     1.   A copy of the articles of association of the Trustee is now in effect
          which includes the authority of the trustee to commence business and
          to exercise corporate trust powers.

          A copy of the Certificate of Merger dated April 1, 1972 between Harris
          Trust and Savings Bank, HTS Bank and Harris Bankcorp, Inc. which
          constitutes the articles of association of the Trustee as now in
          effect and includes the authority of the Trustee to commence business
          and to exercise corporate trust powers was filed in connection with
          the Registration Statement of Louisville Gas and Electric Company,
          File No. 2-44295, and is incorporated herein by reference.

     2.   A copy of the existing by-laws of the Trustee.

          A copy of the existing by-laws of the Trustee was filed in connection
          with the Registration Statement of Commercial Federal Corporation,
          File No. 333-20711, and is incorporated herein by reference.

     3.   The consents of the Trustee required by Section 321(b) of the Act.

          (included as Exhibit A on page 2 of this statement)

     4.   A copy of the latest report of condition of the Trustee published
          pursuant to law or the requirements of its supervising or examining
          authority.

          (included as Exhibit B on page 3 of this statement)

                                        1

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                                    SIGNATURE

Pursuant to the requirements of the Trust Indenture Act of 1939, the Trustee,
HARRIS TRUST AND SAVINGS BANK, a corporation organized and existing under the
laws of the State of Illinois, has duly caused this statement of eligibility to
be signed on its behalf by the undersigned, thereunto duly authorized, all in
the City of Chicago, and State of Illinois, on the 12th day of November, 1998.

HARRIS TRUST AND SAVINGS BANK

By: /s/ C. Potter
   --------------------------------
     C. Potter
     Assistant Vice President

EXHIBIT A

The consents of the trustee required by Section 321(b) of the Act.

Harris Trust and Savings Bank, as the Trustee herein named, hereby consents that
reports of examinations of said trustee by Federal and State authorities may be
furnished by such authorities to the Securities and Exchange Commission upon
request therefor.

HARRIS TRUST AND SAVINGS BANK

By: /s/ C. Potter
   --------------------------------
     C. Potter
     Assistant Vice President

                                        2

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EXHIBIT B

Attached is a true and correct copy of the statement of condition of Harris 
Trust and Savings Bank as of June 30, 1998, as published in accordance with a 
call made by the State Banking Authority and by the Federal Reserve Bank of 
the Seventh Reserve District.

                        [LOGO] HARRIS BANK

                          Harris Trust and Savings Bank
                             111 West Monroe Street
                             Chicago, Illinois 60603

of Chicago, Illinois, And Foreign and Domestic Subsidiaries, at the close of 
business on June 30, 1998, a state banking institution organized and 
operating under the banking laws of this State and a member of the Federal 
Reserve System. Published in accordance with a call made by the Commissioner 
of Banks and Trust Companies of the State of Illinois and by the Federal 
Reserve Bank of this District.

                         Bank's Transit Number 71000288

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                                                                                                    THOUSANDS
                                          ASSETS                                                    OF DOLLARS
<S>                                                                                    <C>              <C>
CASH AND BALANCES DUE FROM DEPOSITORY INSTITUTIONS:
              NON-INTEREST BEARING BALANCES AND CURRENCY AND COIN .................                      $ 1,417,965
              INTEREST BEARING BALANCES ...........................................                      $   303,574
SECURITIES:
a.  HELD-TO-MATURITY SECURITIES ...................................................                      $         0
b.  AVAILABLE-FOR-SALE SECURITIES .................................................                      $ 4,490,777
FEDERAL FUNDS SOLD AND SECURITIES PURCHASED UNDER AGREEMENTS TO RESELL ............                      $   263,100
LOANS AND LEASE FINANCING RECEIVABLES:
              LOANS AND LEASES, NET OF UNEARNED INCOME ............................     $ 9,238,306
              LESS:  ALLOWANCE FOR LOAN AND LEASE LOSSES ..........................     $   103,410
                                                                                        -----------

              LOANS AND LEASES, NET OF UNEARNED INCOME, ALLOWANCE, AND RESERVE
              (ITEM 4.a MINUS 4.b) ................................................                      $ 9,134,896
ASSETS HELD IN TRADING ACCOUNTS ...................................................                      $   192,782
PREMISES AND FIXED ASSETS (INCLUDING CAPITALIZED LEASES) ..........................                      $   230,242
OTHER REAL ESTATE OWNED ...........................................................                      $       244
INVESTMENTS IN UNCONSOLIDATED SUBSIDIARIES AND ASSOCIATED COMPANIES ...............                      $        23
CUSTOMER'S LIABILITY TO THIS BANK ON ACCEPTANCES OUTSTANDING ......................                      $    39,065
INTANGIBLE ASSETS .................................................................                      $   262,703
OTHER ASSETS ......................................................................                      $ 1,090,011
                                                                                                         -----------

TOTAL ASSETS                                                                                             $17,425,382
                                                                                                         -----------
                                                                                                         -----------

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                                        3

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<TABLE>
<CAPTION>

                                        LIABILITIES
<S>                                                                                            <C>           <C>
DEPOSITS:
     IN DOMESTIC OFFICES ....................................................................                 $ 9,411,411
              NON-INTEREST BEARING ..........................................................   $ 3,093,738
              INTEREST BEARING ..............................................................   $ 6,317,673
     IN FOREIGN OFFICES, EDGE AND AGREEMENT SUBSIDIARIES, AND IBF'S .........................                 $ 1,501,440
              NON-INTEREST BEARING ..........................................................   $    33,412
              INTEREST BEARING ..............................................................   $ 1,468,028
FEDERAL FUNDS PURCHASED AND SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE IN DOMESTIC
OFFICES OF THE BANK AND OF ITS EDGE AND AGREEMENT SUBSIDIARIES, AND IN IBF'S:
FEDERAL FUNDS PURCHASED & SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE ....................                 $ 3,465,000
TRADING LIABILITIES                                                                                                83,843
OTHER BORROWED MONEY:
a.  WITH REMAINING MATURITY OF ONE YEAR OR LESS .............................................                 $ 1,016,061
b.  WITH REMAINING MATURITY OF MORE THAN ONE YEAR ...........................................                 $         0
BANK'S LIABILITY ON ACCEPTANCES EXECUTED AND OUTSTANDING ....................................                 $    39,065
SUBORDINATED NOTES AND DEBENTURES ...........................................................                 $   225,000
OTHER LIABILITIES ...........................................................................                 $   408,338
                                                                                                              -----------

TOTAL LIABILITIES                                                                                             $16,150,158
                                                                                                              -----------
                                                                                                              -----------

                                  EQUITY CAPITAL

COMMON STOCK ................................................................................                 $   100,000
SURPLUS .....................................................................................                 $   601,594
a.  UNDIVIDED PROFITS AND CAPITAL RESERVES ..................................................                 $   562,502
b.  NET UNREALIZED HOLDING GAINS (LOSSES) ON AVAILABLE-FOR-SALE SECURITIES...................                 $    11,128
                                                                                                              -----------

TOTAL EQUITY CAPITAL                                                                                          $ 1,275,224
                                                                                                              -----------
                                                                                                              -----------

TOTAL LIABILITIES, LIMITED-LIFE PREFERRED STOCK, AND EQUITY CAPITAL .........................                 $17,245,382
                                                                                                              -----------
                                                                                                              -----------
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     I, Pamela Piarowski, Vice President of the above-named bank, do hereby
declare that this Report of Condition has been prepared in conformance with the
instructions issued by the Board of Governors of the Federal Reserve System and
is true to the best of my knowledge and belief.

                                PAMELA PIAROWSKI
                                     7/30/98

     We, the undersigned directors, attest to the correctness of this Report of
Condition and declare that it has been examined by us and, to the best of our
knowledge and belief, has been prepared in conformance with the instructions
issued by the Board of Governors of the Federal Reserve System and the
Commissioner of Banks and Trust Companies of the State of Illinois and is true
and correct.

                  EDWARD W. LYMAN,
                  ALAN G. McNALLY,
                  RICHARD E. TERRY
                                                                Directors.

                                        4
