
<PAGE>
                                                       REGISTRATION NO. 33-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                              -------------------
                                    FORM S-3
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                              -------------------
                         NORTHERN STATES POWER COMPANY
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

<TABLE>
<S>                     <C>
      MINNESOTA          41-0448030
   (State or other         (I.R.S.
   jurisdiction of        Employer
   incorporation or     Identification
    organization)       No.)
</TABLE>

                414 Nicollet Mall, Minneapolis, Minnesota 55401
              (Address, including zip code, and telephone number,
              including area code, of principal executive offices)

<TABLE>
<S>                                                 <C>
                EDWARD J. MCINTYRE                                   GARY R. JOHNSON
    Vice President and Chief Financial Officer                 Vice President and Secretary
          Northern States Power Company                       Northern States Power Company
                414 Nicollet Mall                                   414 Nicollet Mall
           Minneapolis, Minnesota 55401                        Minneapolis, Minnesota 55401
                  (612) 330-7712                                      (612) 330-7623
</TABLE>

           (Name, address, including zip code, and telephone number,
                   including area code, of agent for service)
                            ------------------------

                                    COPY TO
                                PETER D. CLARKE
                           Gardner, Carton & Douglas
                             321 North Clark Street
                            Chicago, Illinois 60610
                                 (312) 245-8685
                              -------------------

        APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:
   FROM TIME TO TIME AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.
                              -------------------

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

    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. /X/

    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. / /

    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. / /

    If delivery of the prospectus is expected  to be made pursuant to Rule  434,
please check the following box. /X/
                              -------------------

                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                                PROPOSED MAXIMUM       PROPOSED MAXIMUM
       TITLE OF EACH CLASS OF              AMOUNT TO BE          OFFERING PRICE            AGGREGATE              AMOUNT OF
     SECURITIES TO BE REGISTERED            REGISTERED              PER UNIT            OFFERING PRICE        REGISTRATION FEE
<S>                                    <C>                    <C>                    <C>                    <C>
First Mortgage Bonds.................      $300,000,000             $100%(1)            $300,000,000(1)           $103,449
</TABLE>

(1) Estimated solely for the purpose of determining the registration fee.
                              -------------------

    THE  REGISTRANT HEREBY  AMENDS THIS REGISTRATION  STATEMENT ON  SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A  FURTHER  AMENDMENT  WHICH SPECIFICALLY  STATES  THAT  THIS  REGISTRATION
STATEMENT  SHALL THEREAFTER BECOME EFFECTIVE IN  ACCORDANCE WITH SECTION 8(A) OF
THE SECURITIES ACT  OF 1933,  AS AMENDED,  OR UNTIL  THE REGISTRATION  STATEMENT
SHALL  BECOME EFFECTIVE ON SUCH DATE AS  THE COMMISSION, ACTING PURSUANT TO SAID
SECTION 8(A), MAY DETERMINE.

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- --------------------------------------------------------------------------------
<PAGE>
INFORMATION   CONTAINED  HEREIN  IS  SUBJECT   TO  COMPLETION  OR  AMENDMENT.  A
REGISTRATION STATEMENT  RELATING TO  THESE SECURITIES  HAS BEEN  FILED WITH  THE
SECURITIES  AND EXCHANGE  COMMISSION. THESE SECURITIES  MAY NOT BE  SOLD NOR MAY
OFFERS TO BUY BE ACCEPTED PRIOR  TO THE TIME THE REGISTRATION STATEMENT  BECOMES
EFFECTIVE.  THIS  PROSPECTUS  SHALL  NOT  CONSTITUTE AN  OFFER  TO  SELL  OR THE
SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE  SECURITIES
IN  ANY STATE IN WHICH SUCH OFFER,  SOLICITATION OR SALE WOULD BE UNLAWFUL PRIOR
TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF ANY SUCH STATE.
<PAGE>
                  SUBJECT TO COMPLETION, DATED OCTOBER 6, 1995
                                   PROSPECTUS
                         NORTHERN STATES POWER COMPANY
                           (A MINNESOTA CORPORATION)
                              FIRST MORTGAGE BONDS

                                  ------------

    Northern States Power Company, a Minnesota corporation (the "Company"),  may
offer  for sale from time to time  up to $300,000,000 aggregate principal amount
of its First Mortgage Bonds (the "New  Bonds"), in one or more series, on  terms
and  in amounts to  be determined at  the time of  sale. The aggregate principal
amount, rate or rates (or method of calculation) and time or times and place  of
payment  of  interest, maturity  or maturities,  offering price,  any redemption
terms or other specific  terms of the  series of New Bonds  in respect of  which
this  Prospectus is being delivered (the "Offered Bonds") will be set forth in a
supplement to this Prospectus (the "Prospectus Supplement").

    The Company may sell the New Bonds through underwriters or dealers, directly
to a limited number of institutional purchasers or through agents. See "Plan  of
Distribution."  The  Prospectus  Supplement  will set  forth  the  names  of any
underwriters, dealers  or agents  involved in  the distribution  of the  Offered
Bonds  and any applicable commissions  or discounts and the  net proceeds to the
Company from such sale.

                              -------------------

  THESE  SECURITIES   HAVE   NOT  BEEN   APPROVED   OR  DISAPPROVED   BY   THE
   SECURITIES    AND   EXCHANGE   COMMISSION    OR   ANY   STATE   SECURITIES
     COMMISSION  NOR  HAS  THE   SECURITIES  AND  EXCHANGE  COMMISSION   OR
      ANY   STATE   SECURITIES   COMMISSION  PASSED   UPON   THE  ACCURACY
       OR   ADEQUACY    OF    THIS   PROSPECTUS.    ANY    REPRESENTATION
                          TO THE CONTRARY IS A CRIMINAL OFFENSE.

                              -------------------

               THE DATE OF THIS PROSPECTUS IS             , 1995
<PAGE>
    NO  DEALER,  SALESMAN  OR  OTHER  PERSON HAS  BEEN  AUTHORIZED  TO  GIVE ANY
INFORMATION OR  TO  MAKE  ANY  REPRESENTATIONS OTHER  THAN  THOSE  CONTAINED  OR
INCORPORATED  BY  REFERENCE  IN THIS  PROSPECTUS  AND,  IF GIVEN  OR  MADE, SUCH
INFORMATION OR REPRESENTATIONS MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED
BY THE  COMPANY  OR ANY  UNDERWRITER  OR AGENT.  NEITHER  THE DELIVERY  OF  THIS
PROSPECTUS NOR ANY SALE MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES, CREATE AN
IMPLICATION  THAT THERE HAS BEEN  NO CHANGE IN THE  AFFAIRS OF THE COMPANY SINCE
THE DATE HEREOF.  THIS PROSPECTUS  DOES NOT  CONSTITUTE AN  OFFER TO  SELL OR  A
SOLICITATION  OF AN OFFER TO BUY THE NEW BONDS IN ANY JURISDICTION TO ANY PERSON
TO WHOM IT IS UNLAWFUL TO MAKE SUCH OFFER OR SOLICITATION IN SUCH JURISDICTION.

                             AVAILABLE INFORMATION

    The Company is subject to  the informational requirements of the  Securities
Exchange  Act  of  1934, as  amended  (the  "Exchange Act"),  and  in accordance
therewith files  reports,  proxy  statements  and  other  information  with  the
Securities  and  Exchange  Commission (the  "Commission").  Such  reports, proxy
statements and  other  information  on  file can  be  inspected  at  the  public
reference  offices  of  the  Commission currently  at  450  Fifth  Street, N.W.,
Washington, D.C. 20549; 500 West Madison Street, Chicago, Illinois 60661; and  7
World  Trade Center, New  York, New York  10048. Copies of  such material can be
obtained from the Public  Reference Section of the  Commission at its  principal
office  at 450 Fifth Street, N.W.,  Washington, D.C. 20549, at prescribed rates.
In addition,  reports,  proxy  material and  other  information  concerning  the
Company may be inspected at the Library of the New York Stock Exchange, 20 Broad
Street,  New York, New  York, at the  office of the  Chicago Stock Exchange, 440
South LaSalle Street, Chicago, Illinois, and at the office of the Pacific  Stock
Exchange,  301 Pine  Street, San Francisco,  California, on  which exchanges the
Company's Common Stock is listed. The Company is not required to, and does  not,
provide  annual reports  to holders of  its debt  securities unless specifically
requested by a holder.

    The Company has filed with the  Commission a registration statement on  Form
S-3  (herein,  together with  all amendments  and exhibits,  referred to  as the
"Registration Statement") under  the Securities  Act of 1933,  as amended.  This
Prospectus does not contain all of the information set forth in the Registration
Statement,  certain parts of which are omitted  in accordance with the rules and
regulations of the Commission. For further information, reference is made to the
Registration Statement.

                      DOCUMENTS INCORPORATED BY REFERENCE

    The following  documents  filed  by  the Company  with  the  Commission  are
incorporated by reference into this Prospectus:

        1.  The Company's Annual Report on Form 10-K for the year ended December
           31, 1994;

        2.   The Company's Quarterly Reports on Form 10-Q for the quarters ended
           March 31, 1995  and June 30,  1995 (and Amendments  thereto (on  Form
           10-Q/A) dated August 4, 1995 and August 7, 1995); and

        3.   The Company's Current  Reports on Form 8-K  dated January 30, 1995,
           February 28, 1995,  April 28,  1995, June  27, 1995,  June 28,  1995,
           September 1, 1995 and September 13, 1995.

    All  documents filed by the Company pursuant  to Section 13(a), 13(c), 14 or
15(d) of the Exchange  Act after the  date of this Prospectus  and prior to  the
termination  of this offering shall be deemed to be incorporated by reference in
this Prospectus  from  the date  of  filing  of such  documents.  Any  statement
contained  in a document incorporated or  deemed to be incorporated by reference
in this Prospectus shall be deemed to be modified or superseded for purposes  of
this  Prospectus to the extent that a  statement contained in this Prospectus or
in any  other subsequently  filed document  which also  is or  is deemed  to  be
incorporated  by  reference  in  the  Prospectus  modifies  or  supersedes  such
statement. Any statement so modified or  superseded shall not be deemed,  except
as so modified or superseded, to constitute a part of this Prospectus.

    THE  COMPANY  WILL  PROVIDE WITHOUT  CHARGE  TO EACH  PERSON  (INCLUDING ANY
BENEFICIAL OWNER) TO WHOM A COPY OF THIS PROSPECTUS HAS BEEN DELIVERED, UPON THE
WRITTEN OR  ORAL REQUEST  OF  ANY SUCH  PERSON, A  COPY  OF ANY  OR ALL  OF  THE
DOCUMENTS  REFERRED TO ABOVE WHICH HAVE  BEEN INCORPORATED IN THIS PROSPECTUS BY
REFERENCE, OTHER  THAN EXHIBITS  TO  SUCH DOCUMENTS.  REQUESTS FOR  SUCH  COPIES
SHOULD  BE DIRECTED TO  THE ASSISTANT SECRETARY,  NORTHERN STATES POWER COMPANY,
414 NICOLLET MALL, MINNEAPOLIS, MINNESOTA 55401 (612-330-5994).

                                       2
<PAGE>
                                      [LOGO]

    Northern States Power Company (the "Company") was incorporated in 1909 under
the  laws of Minnesota. Its executive offices  are located at 414 Nicollet Mall,
Minneapolis, Minnesota 55401. (Phone  612-330-5500). The Company's  subsidiaries
include  Northern States Power Company, an operating public utility incorporated
in  Wisconsin   ("NSP-Wisconsin"),  NRG   Energy,  Inc.   ("NRG"),  a   Delaware
corporation,  and  Viking  Gas  Transmission  Company,  a  Delaware  corporation
("Viking"). The Company and its subsidiaries collectively are referred to herein
as NSP.

    NSP is predominantly an operating public utility engaged in the  generation,
transmission  and distribution  of electricity  throughout a  49,000 square mile
service  area  and  the  distribution  of  natural  gas  in  approximately   148
communities  within this  area. Viking is  a regulated  natural gas transmission
company that  operates  a  500-mile  interstate natural  gas  pipeline.  NRG  is
primarily   engaged   in  managing   several   of  NSP's   non-regulated  energy
subsidiaries.

    The Company serves customers  in Minnesota, North  Dakota and South  Dakota.
NSP-Wisconsin  serves customers in Wisconsin  and Michigan. Of the approximately
three million people served by the  Company and NSP-Wisconsin, the majority  are
concentrated  in the Minneapolis-St.  Paul Metropolitan Area.  In 1994, about 61
percent of  NSP's  electric  retail  revenue  was  derived  from  sales  in  the
Minneapolis-St. Paul Metropolitan Area and about 56 percent of gas revenues came
from sales in the St. Paul area. NSP's electric generation for 1994 was provided
for  by  coal (59%),  nuclear (36%),  and  renewable and  other fuels  (5%). NSP
currently operates three nuclear units that were placed in service in 1971, 1973
and 1974. NSP has no additional nuclear units under construction.

                                PROPOSED MERGER

    The Company, Wisconsin Energy Corporation, a Wisconsin corporation  ("WEC"),
Northern  Power  Wisconsin  Corp.,  a  Wisconsin  corporation  and  wholly-owned
subsidiary  of  the  Company  ("New  NSP"),  and  WEC  Sub  Corp.,  a  Wisconsin
corporation and wholly-owned subsidiary of WEC ("WEC Sub"), have entered into an
Agreement  and Plan  of Merger, dated  as of April  28, 1995 and  as amended and
restated as of  July 26,  1995 (the "Merger  Agreement"), which  provides for  a
strategic  business combination  involving NSP  and WEC  in a "merger-of-equals"
transaction (the "Transaction"). The Transaction, which was unanimously approved
by the Boards  of Directors  of the constituent  companies and  approved by  the
shareholders of both the Company and WEC, is expected to close shortly after all
of  the conditions to  the consummation of  the Transaction, including obtaining
applicable regulatory  approvals, are  met or  waived. The  regulatory  approval
process is expected to take approximately 12 to 18 months from April 28, 1995.

    Additional  information concerning the Transaction and the Merger Agreement,
including pro forma combined financial information, is included in the Company's
Quarterly Report on Form 10-Q for the quarter ended June 30, 1995 and Amendments
thereto (on Form  10-Q/A) dated August  4, 1995  and August 7,  1995 (the  "Form
10-Q")  filed  with  the  Commission and  incorporated  by  reference  into this
Prospectus.

    In the Transaction, the holding company  of the combined enterprise will  be
registered under the Public Utility Holding Company Act of 1935, as amended. The
holding  company will be named Primergy Corporation ("Primergy") and will be the
parent company  of  both  the  Company  (which,  for  regulatory  reasons,  will
reincorporate  in Wisconsin) and of  WEC's present principal utility subsidiary,
Wisconsin Electric  Power Company  ("WEPCO") which  will be  renamed  "Wisconsin
Energy  Company." Wisconsin Energy Company will  include the operations of WEC's
other present  utility  subsidiary,  Wisconsin Natural  Gas  Company,  which  is
anticipated  to be merged into WEPCO by  January 1, 1996, as previously planned.
It is  anticipated  that, following  the  Transaction, the  Company's  Wisconsin
utility  subsidiary, NSP-Wisconsin, will be merged into Wisconsin Energy Company
and that NRG and  the Company's other subsidiaries  will become subsidiaries  of
Primergy.

                                       3
<PAGE>
    As  noted above, pursuant to the  Transaction the Company will reincorporate
in Wisconsin for regulatory reasons.  This reincorporation will be  accomplished
by  the merger  of the Company  into New NSP,  with New NSP  being the surviving
corporation and succeeding to the business of the Company as an operating public
utility. Following such merger, WEC  Sub will be merged  with and into New  NSP,
with  New  NSP being  the  surviving corporation  and  becoming a  subsidiary of
Primergy. Both New NSP and  WEC Sub were created  to effect the Transaction  and
will  not have any  significant operations, assets or  liabilities prior to such
mergers.

    The Transaction  is  subject  to customary  closing  conditions,  including,
without  limitation, the receipt of all necessary governmental approvals and the
making of all necessary governmental filings, all as more fully described in the
Form 10-Q.

    A preliminary estimate  indicates that  the Transaction will  result in  net
savings  of approximately $2.0 billion in costs over 10 years. It is anticipated
that the  synergies  created by  the  Transaction  will allow  the  Company  and
Wisconsin  Energy Company  to implement  a modest  reduction in  electric retail
rates followed by a rate freeze  for electric retail customers through the  year
2000.  Both the Company and WEC recognize that the divestiture of their existing
gas operations and certain non-utility operations is a possibility under the new
registered holding company structure, but will seek approval from the Commission
to  maintain  such  businesses.  If  divestiture  is  ultimately  required,  the
Commission  has  historically allowed  companies  sufficient time  to accomplish
divestitures in a manner that protects shareholder value.

    Following the  completion of  the  Transaction, the  Offered Bonds  and  the
Company's other outstanding first mortgage bonds will be obligations of New NSP,
as a subsidiary of Primergy, and will continue to be secured by the Indenture as
described  in  this Prospectus.  However,  as described  above,  New NSP  is not
expected to retain any of the Company's subsidiaries and the Offered Bonds  will
not  be an obligation of  Primergy or any other  subsidiary of Primergy. For the
twelve months ended  June 30, 1995  and the  year ended December  31, 1994,  the
Company's subsidiaries constituted 33% and 29% of NSP's consolidated net income,
respectively,  and represented 22% of NSP's consolidated assets and 17% of NSP's
consolidated liabilities including  long-term debt  at June 30,  1995. The  Form
10-Q filed with the Commission and incorporated by reference in this Prospectus,
includes   pro  forma  financial   information  for  the   Company  without  its
subsidiaries.

                                USE OF PROCEEDS

    The proceeds from the  sale of the  New Bonds will be  added to the  general
funds  of the Company and used for general corporate purposes, which may include
the purchase or redemption of one  or more series of outstanding first  mortgage
bonds  and  the  repayment  of  outstanding  short-term  borrowings  incurred in
connection with NSP's continuing construction program. Short-term borrowings  of
the  Company  aggregated  $169  million  as of  August  31,  1995.  The specific
allocation of the proceeds of a particular  series of the Offered Bonds will  be
described in the Prospectus Supplement.

                    NSP'S RATIO OF EARNINGS TO FIXED CHARGES

<TABLE>
<CAPTION>
                                                      YEAR ENDED DECEMBER 31,
                                                    ----------------------------
                                                    1994  1993  1992  1991  1990
                                  TWELVE MONTHS     ----  ----  ----  ----  ----
                                      ENDED
                                  JUNE 30, 1995
                                ------------------
                                   (UNAUDITED)
<S>                             <C>                 <C>   <C>   <C>   <C>   <C>
Ratio of Earnings to Fixed
 Charges......................              3.8     4.0   4.0   3.2   3.9   3.7
New NSP Pro Forma Ratio of
 Earnings to Fixed Charges....              3.8     4.2   4.0   3.1
</TABLE>

    For  purposes  of computing  the  ratio of  earnings  to fixed  charges, (i)
earnings consist of income from  continuing operations before accounting  change
plus fixed charges, federal and state income taxes,

                                       4
<PAGE>
deferred  income taxes and investment tax  credits and less undistributed equity
in earnings  of unconsolidated  investees;  and (ii)  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.

    The New NSP unaudited pro forma ratios of earnings to fixed charges for each
of the years in the  three-year period ended December  31, 1994, and the  twelve
months ended June 30, 1995, give effect to the Transaction as if it had occurred
at  January 1, 1992.  See the Notes  to Unaudited Pro  Forma Condensed Financial
Statements of New NSP in the Form 10-Q for a description of the assumptions used
to prepare the unaudited pro forma ratios of earnings to fixed charges.

    Assuming that  variable  interest  rate debt  continues  at  interest  rates
applicable  on June 30, 1995, the  annual interest requirement on long-term debt
of NSP outstanding at June 30, 1995, was $108,336,000.

                            DESCRIPTION OF NEW BONDS

    Each series of New Bonds is to be an initial issue of a new series of  first
mortgage  bonds (the "Bonds") issued under the Trust Indenture dated February 1,
1937 (the "1937 Indenture") as supplemented by 44 supplemental trust  indentures
(collectively, the "Supplemental Indentures"), a Supplemental and Restated Trust
Indenture  dated May 1,  1988 (the "Restated Indenture")  and a new supplemental
trust indenture for such series of New Bonds (the "New Supplemental Indenture"),
all from  the  Company  to  Harris  Trust and  Savings  Bank,  as  trustee  (the
"Trustee").  The 1937 Indenture, as supplemented by the Supplemental Indentures,
the Restated Indenture and the New Supplemental Indenture herein are referred to
collectively as  the "Indenture."  Excluding the  New Bonds,  there will  be  14
series  of Bonds in an aggregate  principal amount of $1,094,800,000 outstanding
under the Indenture. Copies of the 1937 Indenture, the Supplemental  Indentures,
the  Restated Indenture and the form of the New Supplemental Indenture are filed
as Exhibits 4.01A  to 4.01UU to  the Registration Statement  and the  statements
herein made (being for the most part succinct summaries of certain provisions of
the Indenture) are subject to the detailed provisions of the 1937 Indenture, the
Supplemental  Indentures,  the  Restated  Indenture  and  the  New  Supplemental
Indenture which are incorporated herein by reference.

    The Restated  Indenture  amends and  restates  the 1937  Indenture  and  the
Supplemental  Indentures. The Restated  Indenture will not  become effective and
operative until all Bonds of each series issued under the Indenture prior to May
1, 1988 shall have been retired  through payment or redemption (including  those
Bonds  "deemed to be  paid" within the meaning  of that term  as used in Article
XVII of the 1937 Indenture) or (except as described below) until the holders  of
the  requisite  principal  amount of  such  Bonds  shall have  consented  to the
amendments contained in the Restated  Indenture (herein, the "Effective  Date").
Holders  of the New Bonds and of each series of Bonds issued under the Indenture
after May 1,  1988 likewise will  be bound  by the amendments  contained in  the
Restated  Indenture when they become effective  and operative. If the consent of
the holders of Bonds of each series issued prior to May 1, 1988 is not  obtained
or  such Bonds are  not retired prior  to their maturity,  the Company presently
expects the Restated Indenture to become  effective no earlier than December  1,
2006.

    The  following summary  of the provisions  of the  Indenture includes, where
applicable, a discussion of the amendments contained in the Restated  Indenture.
References  are  made  to  specific  Article and  Section  numbers  of  the 1937
Indenture, the  Supplemental  Indentures, the  Restated  Indenture and  the  New
Supplemental Indenture. Unless the context indicates otherwise, words or phrases
defined  in  the  1937  Indenture,  the  Supplemental  Indentures,  the Restated
Indenture or the New  Supplemental Indenture are capitalized  and used with  the
same meanings herein.

TERMS OF NEW BONDS

    The  New Bonds will be  issued as fully registered  bonds without coupons in
denominations of multiples of $1,000. New Bonds may be issued in temporary  form
if,  for any reason,  the Company is  unable to deliver  New Bonds in definitive
form. Principal and interest are to  be payable in Chicago, Illinois, at  Harris
Trust  and Savings Bank or in New York,  New York at Harris Trust Company of New
York.

                                       5
<PAGE>
New Bonds will be interchangeable  in the manner provided  in Article II of  the
New  Supplemental  Indenture. The  New Bonds  may be  issued in  book-entry form
through the  facilities  of a  depository.  The description  of  any  book-entry
arrangements will be contained in the Prospectus Supplement.

    No  charge will be made  by the Company for any  exchange or transfer of New
Bonds, other than for any taxes or other governmental charges.

    Reference is  made to  the Prospectus  Supplement that  will accompany  this
Prospectus  for the  following terms and  other information with  respect to the
Offered Bonds:  (1)  the designation  and  aggregate principal  amount  of  such
Offered  Bonds; (2) the date  or dates on which  such Offered Bonds will mature;
(3) the rate or rates per annum (or method of calculation) at which such Offered
Bonds will bear interest and the date from which such interest shall accrue; (4)
the dates on  which such  interest will  be payable;  (5) the  record dates  for
payments  of interest;  and (6)  any optional  or mandatory  redemption terms or
other specific  terms  applicable to  the  Offered  Bonds. The  holders  of  the
outstanding  Bonds do not, and  the holders of the New  Bonds will not, have the
right to  tender such  Bonds to  the  Company for  repurchase upon  the  Company
becoming  involved in a  highly leveraged or change  in control transaction. The
Indenture does not have any provision that is designed specifically in  response
to  highly  leveraged or  change in  control transactions.  However, bondholders
would have the security afforded by the first mortgage lien on substantially all
the Company's  property as  described  under the  subcaption "Security  for  New
Bonds"  below. In addition, any change in control transaction and any incurrence
of additional indebtedness (as first mortgage bonds or otherwise) by the Company
in such  a  transaction  would  require approval  of  state  utility  regulatory
authorities and, possibly, of federal utility regulatory authorities. Management
believes  that such  approvals would be  unlikely in any  transaction that would
result in the Company, or a successor to the Company, having a highly  leveraged
capital structure. See "PROPOSED MERGER."

SECURITY FOR NEW BONDS

    In the opinion of counsel for the Company, the New Bonds when issued will be
secured  equally and  ratably, except  as to  sinking fund  provisions, with all
other outstanding Bonds by a valid and direct first mortgage lien on all of  the
real  and fixed properties, leasehold rights,  franchises and permits then owned
by the Company subject only  (a) to Permitted Liens and  (b) as to parts of  the
Company's  property, to certain easements,  conditions, restrictions, leases and
similar encumbrances which do not affect  the Company's use of such property  in
the  usual course of its business, to  certain minor defects in titles which are
not material and to defects in titles to certain properties not essential to the
Company's business. The Indenture contains provisions for subjecting to the lien
thereof all  property,  rights and  franchises  (except as  otherwise  expressly
provided)  acquired by the  Company after the  date of the  1937 Indenture. Such
provisions might not be effective as to property acquired, within 90 days  prior
and  subsequent to the filing of a case,  with respect to the Company, under the
United States Bankruptcy Code. The opinion  of counsel does not cover titles  to
easements  for  water flowage  purposes or  rights-of-way  for electric  and gas
transmission and  distribution  facilities,  steam mains  and  telephone  lines.
However,  the Company has the power of eminent  domain in the states in which it
operates.

    The Indenture provides that no prior liens, other than Permitted Liens,  may
be created or permitted to exist upon the mortgaged and pledged property whether
now  owned  or  hereafter acquired.  (Section  4  of Article  VIII  of  the 1937
Indenture.) Following the retirement of the Bonds of each series issued prior to
May 1, 1988, the Restated Indenture will amend the foregoing provisions to allow
Permitted  Encumbrances  on  the  mortgaged  and  pledged  property.   Permitted
Encumbrances  include Permitted Liens and (a)  rights of Persons who are parties
to agreements with the  Company relating to property  owned or used jointly  (in
common)  by the Company with such Persons,  provided (i) that such rights do not
materially impair the use of such jointly  owned or used property in the  normal
operation  of the Company's  business and do not  materially affect the security
afforded by the Indenture  and (ii) that such  rights are not inconsistent  with
the remedies of the Trustee upon a Completed Default; (b) (i) leases existing at
the  Effective Date  of the Restated  Indenture affecting property  owned by the
Company on  the  Effective Date;  (ii)  leases which  do  not interfere  in  any
material respect with the use of the related

                                       6
<PAGE>
property  for the purpose for which it is held by the Company and which will not
have a material  adverse impact  on the security  afforded by  the Indenture  or
(iii)  other leases  relating to not  more than 5%  of the sum  of the Company's
Depreciable Property and Land; and (c) any mortgage, lien, charge or encumbrance
prior or equal to the Lien of the Indenture, other than a Prepaid Lien, existing
at the date any property is acquired  by the Company, provided that at the  date
of  acquisition of such property: (i) no Default has occurred and is continuing;
(ii) the principal amount of indebtedness outstanding under and secured by  such
mortgage,  lien, charge or encumbrance shall not exceed 66 2/3% of the lesser of
the Cost  or  Fair Value  of  the property  so  acquired; and  (iii)  each  such
mortgage,  lien,  charge or  encumbrance shall  apply only  to the  property and
improvements originally subject thereto and that  the Company shall cause to  be
closed  all mortgages or other liens existing  at the time of acquisition of any
property thereafter  acquired  by the  Company  and will  permit  no  additional
indebtedness  to be issued  thereunder or secured thereby.  (Section 1.03 of the
Restated Indenture.)

    Following the retirement of the Bonds of each series issued prior to May  1,
1988,  the holders of 66  2/3% of the principal  amount of Bonds Outstanding may
(a) consent to the creation or existence of  a Prior Lien with respect to up  to
50%  of the  sum of  the Company's Depreciable  Property and  Land, after giving
effect to  such Prior  Lien or  (b) terminate  the Lien  of the  Indenture  with
respect  to up to 50% of the sum of the Company's Depreciable Property and Land.
(Section 18.02(e) of the Restated Indenture.)

    The Indenture is not a lien on  the properties of NSP-Wisconsin, nor is  the
stock of NSP-Wisconsin, NRG, Viking or any other subsidiary owned by the Company
pledged thereunder.

SINKING FUND PROVISIONS

    The  sinking fund redemption provision,  if any, for each  series of the New
Bonds will  be set  forth in  the related  Prospectus Supplement.  As an  annual
sinking  fund, the Company covenants to pay  to the Trustee annually, on October
1, an amount sufficient to redeem, for sinking fund purposes, 1% of the  highest
amount, at any time outstanding, of each outstanding series of Bonds, other than
Bonds  of the Series due October 1, 1997, Bonds of the Series due April 1, 2003,
Bonds of the Series due  December 1, 2000, Bonds of  the Series due December  1,
2005,  Bonds of the Series due February 1, 1999, Bonds of the Series due October
1, 2001, Bonds of the Series due  July 1, 2025 and other than Pollution  Control
Series  C, J, K, L and Resource Recovery  Series I. Sinking fund payments may be
offset by (a) application of  net Permanent Additions of  a Cost or Fair  Value,
whichever  is  less,  equal to  150%  of  the principal  amount  of  Bonds which
otherwise would be required to be retired by the sinking fund or (b)  retirement
or  delivery to the Trustee of Bonds of the series for which the sinking fund is
applicable. The Trustee is required to apply sinking fund money to the  purchase
or  redemption  of Bonds  of  the series  for  which such  money  is applicable.
(Article III of  each Supplemental Indenture  except those dated  June 1,  1942,
February 1, 1944, October 1, 1945, July 1, 1948, August 1, 1949, August 1, 1957,
October  1, 1992, April 1, 1993, December  1, 1993, February 1, 1994, October 1,
1994, June 1, 1995 and  those relating to each  Pollution Control Series and  to
Resource Recovery Series I.)

    Certain  of  the  Bonds of  Resource  Recovery  Series I  are  subject  to a
mandatory sinking fund applicable  to each respective  series. (Section 3.02  of
the Supplemental Indenture dated December 1, 1984.)

MAINTENANCE PROVISIONS

    As  a Maintenance Fund  for the Bonds,  the Company covenants  to pay to the
Trustee annually on  May 1  an amount  equal to  15% of  the Consolidated  Gross
Operating  Revenues  of  the  Company for  the  preceding  calendar  year, after
deducting from such  revenues: (a)  cost of  electricity and  gas purchased  for
resale,  (b) rentals  paid for utility  property, less credits  at the Company's
option for  (i)  maintenance,  (ii) property  retirements  offset  by  Permanent
Additions,  (iii) retirements of Bonds and (iv) Cost or Fair Value, whichever is
less, of Permanent Additions  after deducting property retirements.  Withdrawals
from  the Maintenance Fund may be made on  the basis of retirements of Bonds and
net Permanent Additions, but cash in excess of $100,000 remaining on deposit  in
the  Maintenance Fund for more than three years must be used for the purchase or
redemption  of  Bonds.  Any   such  redemption  would   be  at  the   applicable

                                       7
<PAGE>
regular  redemption  price  of the  Bonds  to  be redeemed  and  subject  to any
restrictions on the redemption of such Bonds. (Article IX of the 1937 Indenture;
Article IV of the Supplemental Indenture dated June 1, 1952.)

    The Restated Indenture will amend the foregoing provisions of the  Indenture
by  replacing the current Maintenance Fund  deposit formula with the requirement
that the Company pay to the Trustee annually  on May 1 an amount equal to  2.50%
of  its Completed Depreciable Property  as of the end  of the preceding calendar
year, after deducting credits at the  Company's option for (a) maintenance,  (b)
property retirements offset by Permanent Additions, (c) retirements of Bonds and
(d)  Amounts of Established  Permanent Additions. (Section  9.01 of the Restated
Indenture.) The  Restated Indenture  further provides  that to  the extent  that
Maintenance  Fund credits exceed 2.50% of Completed Depreciable Property for any
year after 1987,  such excess  credits may  be applied  in future  years (a)  to
offset  any  Maintenance  Fund  deficiency  or (b)  to  increase  the  Amount of
Established Permanent Additions available for use under the Indenture.  (Section
9.05  of the Restated Indenture.) In addition, the Restated Indenture eliminates
the requirement that  cash in  excess of $100,000  remaining on  deposit in  the
Maintenance  Fund  for  more  than  three years  be  used  for  the  purchase or
redemption of Bonds.

    The Company has covenanted  to maintain its  properties in adequate  repair,
working  order and condition. (Section 6 of  Article VIII of the 1937 Indenture;
Section 8.06 of the Restated Indenture.)

ISSUANCE OF ADDITIONAL BONDS

    The maximum principal amount of Bonds that may be issued under the Indenture
is not limited, except as described below. Additional Bonds may be issued on the
basis of (a)  60% of the  Cost or Fair  Value, whichever is  less, of  Permanent
Additions  after deducting  retirements (Article V  of the  1937 Indenture; also
Sections 1 and 3 of Article III of the Supplemental Indenture dated February  1,
1944); (b) retired Bonds, which have not been otherwise used under the Indenture
(Article  VI of the 1937 Indenture); and (c)  deposit of an equal amount of cash
with the Trustee, which cash  may be withdrawn on  the same basis as  additional
Bonds  may be issued under  clauses (a) and (b) above.  (Article VII of the 1937
Indenture; Section 2 of Article III of the Supplemental Indenture dated February
1, 1944; and Article IV of the  Supplemental Indenture dated June 1, 1952.)  The
Restated  Indenture  will amend  the foregoing  provisions  of the  Indenture by
increasing the percentage in clause (a) above from 60% to 66 2/3%. (Section 5.03
of the Restated Indenture.)

    The New Bonds will be  issued under clause (a)  and/or (b) above. At  August
31,  1995, the amount of  net Permanent Additions available  for the issuance of
Bonds exceeded  $4.2  billion, of  which  $500 million  could  be used  for  the
authentication  of $300 million principal amount of  the New Bonds. As of August
31, 1995, $327 million of retired Bonds were available for the authentication of
up to $327 million of New Bonds.

    No additional Bonds may  be issued on  the basis of  clause (a), clause  (b)
under  specified conditions,  or clause (c),  unless the  Earnings Applicable to
Bond Interest for a specified twelve-month period are equal to twice the  annual
interest requirements on the Bonds, including those about to be issued. (Section
4  of Article V, Section  2 of Article VI,  and Section 1 of  Article VII of the
1937 Indenture.)

    Permanent Additions include:  the Company's electric  and steam  generating,
transmission   and  distribution  properties;  the  Company's  gas  storage  and
distribution  properties;  construction  work-in-progress;  and  fractional  and
undivided property interests of the Company. (Section 4 of Article I of the 1937
Indenture;   Section  1.03  of  the  Restated  Indenture.)  Under  the  Restated
Indenture, Permanent Additions  also will  include property  used for  providing
telephone  or other communication services and engineering, financial, economic,
environmental, geological  and  legal  or  other  studies,  surveys  or  reports
associated  with the  acquisition or  construction of  any Depreciable Property.
(Section 1.03 of the Restated Indenture.)

    Assuming that the  interest cost on  variable rate Bonds  is at the  maximum
allowable rate, Earnings Applicable to Bond Interest for the twelve months ended
August  31, 1995,  would be  4.9 times the  annual interest  requirements on the
Bonds including  the  New Bonds  at  an  assumed 8%  interest  rate.  Additional

                                       8
<PAGE>
Bonds  may vary from the Offered Bonds as to maturity, interest rate, redemption
prices, and sinking fund, and in certain other respects. (Article II of the 1937
Indenture and Article II of the Restated Indenture.) The Restated Indenture will
amend the Indenture by requiring that Earnings Applicable to Bond Interest for a
specified twelve-month period be equal to twice the annual interest requirements
on the Bonds, including those about to be issued, and any obligations secured by
Prior Liens and  any indebtedness secured  by Permitted Encumbrances.  (Sections
1.03  and 5.04  of the  Restated Indenture.)  Under the  Restated Indenture, the
calculation of Earnings Applicable to Bond Interest will include all non-utility
revenues of the Company. (Section 1.03 of the Restated Indenture.)

PROVISION LIMITING DIVIDENDS ON COMMON STOCK

    The  Company  has  covenanted  that  the  sum  of  (i)  all  dividends   and
distributions on the common stock of the Company after September 30, 1954 (other
than  in common  stock), and  (ii) the cost  of all  shares of  its common stock
acquired by  it after  that date  shall not  exceed the  sum of  (a) the  earned
surplus  of the Company and its Qualified Subsidiary Companies, consolidated, at
September 30, 1954, and (b)  an amount equal to  the consolidated net income  of
the  Company and its Qualified Subsidiary  Companies, earned after September 30,
1954, after  making provision  for all  dividends accruing  after that  date  on
preferred  stock of the  Company and after taking  into consideration all proper
charges and credits  to earned surplus  made after that  date. In computing  net
income  for the purpose of  this covenant, there will  be deducted an amount, if
any, by  which  15%  of  the  Consolidated  Gross  Operating  Revenues  of  such
companies,  after  certain  deductions,  exceeds the  aggregate  of  the amounts
expended  for   maintenance  and   appropriated  for   reserves  for   renewals,
replacements,  retirements,  depreciation  or  depletion.  (Article  IV  of  the
Supplemental Indenture dated October 1, 1954.) As of 1957, the Company no longer
had any  Qualified Subsidiary  Companies. This  provision has  not impaired  the
Company's  ability to pay dividends in the past  and is not expected to do so in
the future.

    The Restated Indenture will replace the dividend restriction described above
with the requirement that (a) the sum of: (i) all dividends and distributions on
the Company's common stock  after the Effective Date  of the Restated  Indenture
(other  than  in  common  stock) and  (ii)  the  amount, if  any,  by  which the
Considerations given by the Company for the purchase or other acquisition of its
common stock after the Effective Date exceeds the Considerations received by  it
after the Effective Date from the sale of common stock, shall not exceed (b) the
sum  of (i) the retained earnings of the Company at the Effective Date, and (ii)
an amount equal  to the net  income of  the Company earned  after the  Effective
Date,  after deducting  all dividends accruing  after the Effective  Date on all
classes and  series of  preferred stock  of the  Company and  after taking  into
consideration  all proper charges  and credits to earned  surplus made after the
Effective Date.  In  computing  net  income for  the  purpose  of  this  amended
covenant,  there will be deducted  the amount, if any,  by which, after the date
commencing 365 days  prior to  the Effective  Date, the  actual expenditures  or
charges  for  ordinary repairs  and maintenance  and  the charges  for reserves,
renewals, replacements, retirements,  depreciation and depletion  are less  than
2.50%  of the  Company's Completed  Depreciable Property.  (Section 8.07  of the
Restated Indenture.)

RELEASE PROVISIONS

    The Indenture contains provisions  permitting the release  from its lien  of
any  property  upon depositing  or pledging  cash or  certain other  property of
comparable Fair Value. The  Indenture also contains provisions  for the sale  or
other  disposal  of  securities  not  pledged  under  the  Indenture, contracts,
accounts, motor cars, and certain equipment and supplies; for the  cancellation,
change  or  alteration  of  leases, rights-of-way  and  easements;  and  for the
surrender and modification of any  franchise or governmental consent subject  to
certain restrictions; in each case without any release or consent by the Trustee
or  accountability  thereto  for  any  consideration  received  by  the Company.
(Article XI of the 1937 Indenture and Article XI of the Restated Indenture.)

    Following the retirement of the Bonds of each series issued prior to May  1,
1988,  (a) the Company may sell or otherwise dispose of, free of the Lien of the
Indenture, all  motor vehicles,  vessels and  marine equipment,  railroad  cars,
engines  and  related  equipment,  airplanes,  office  furniture  and  leasehold
interests in property owned by third parties and (b) the Company may enter  into
leases with respect to

                                       9
<PAGE>
the  property subject to the Lien of the Indenture which do not interfere in any
material respect with the use of such  property for the purpose for which it  is
held  by the Company and will not have a material adverse impact on the security
afforded by the Indenture. (Section 11.02(b) of the Restated Indenture.)

    Following the retirement of the Bonds of each series issued prior to May  1,
1988, any of the mortgaged and pledged property may be released from the Lien of
the  Indenture if, after such release, the Fair Value of the remaining mortgaged
and pledged property  equals or exceeds  a sum  equal to 150%  of the  aggregate
principal  amount  of  Bonds  Outstanding.  (Section  11.03(k)  of  the Restated
Indenture.) When effective and upon  satisfaction of the requirements set  forth
in  the  Indenture,  this provision  would  permit  the Company  to  spin-off or
otherwise dispose  of a  substantial amount  of  assets or  a line  of  business
without depositing cash or property with the Trustee or obtaining the consent of
the bondholders.

MODIFICATION OF THE INDENTURE

    With  the consent  of the  Company, the provisions  of the  Indenture may be
changed by the affirmative vote of the holders of 80% in principal amount of the
Bonds Outstanding except that,  among other things, the  maturity of a Bond  may
not  be  extended,  the interest  rate  reduced,  nor the  terms  of  payment of
principal or interest changed without the consent of the holder of each Bond  so
affected. (Article XVIII of the 1937 Indenture.)

    The   Supplemental  Indenture  dated  May  1,  1985  amended  the  foregoing
provisions of the  Indenture by reducing  the 80% requirement  to 66 2/3%.  This
amendment will not become effective and operative until all Bonds of each series
issued  prior to May  1, 1985 shall have  been retired or  until all the holders
thereof shall have consented to such amendment. Holders of the New Bonds and  of
each  subsequent series issued under the Indenture will likewise be bound by the
amendment  when  it  becomes  effective  and  operative.  (Article  VI  of   the
Supplemental  Indenture  dated May  1, 1985  and Section  18.02 of  the Restated
Indenture.)

CONCERNING THE TRUSTEE

    In case of a Completed Default either  the Trustee or the holders of 25%  in
principal amount of (i) the Bonds Outstanding or (ii) the Bonds affected by such
default,  may declare  the Bonds  due and  payable subject  to the  right of the
holders of a majority  of the Bonds  then Outstanding to  rescind or annul  such
action.  Further, it is obligatory upon the Trustee to take the actions provided
in the Indenture to enforce payment of  the Bonds and the Lien of the  Indenture
upon  being requested to do so by the  holders of a majority in principal amount
of the Bonds.  However, the holders  of a  majority in principal  amount of  the
Bonds may direct the taking of any such action or the refraining therefrom as is
not  contrary  to law  or the  Indenture.  As a  condition precedent  to certain
actions, the Trustee may require adequate indemnity against the costs,  expenses
and  liabilities to be  incurred therein or  thereby. (Article XIII  of the 1937
Indenture; Section 6 of Article VI  of Supplemental Indenture dated February  1,
1944;  Section 4.03 of Supplemental Indenture  dated October 1, 1945 and Article
XIII of the Restated Indenture.)

DEFAULTS

    The following is a summary of  events defined in the Indenture as  Completed
Defaults: (a) default in payment of principal of any Bond, (b) default continued
for  90 days  in payment of  interest on any  Bond, (c) default  in the covenant
contained in Section 11 of  Article VIII of the  Indenture (Section 8.11 of  the
Restated  Indenture)  with  respect  to  bankruptcy,  insolvency,  assignment or
receivership and  (d)  default  continued  for  90  days  after  notice  in  the
performance  of any other covenant, agreement or condition. (Section 4.02 of the
Supplemental Indenture dated October 1, 1945  and Section 13.01 of the  Restated
Indenture.)

    The  Trustee is required  to give notice  to bondholders (1)  within 90 days
after the occurrence of a  default known to the  Trustee within such period,  or
(2)  if the Trustee is unaware of a  default during such period, then, within 30
days after the  Trustee knows of  such default, unless  such default shall  have
been  cured before giving  such notice; provided  that, except in  the case of a
default resulting  from the  failure to  make  any payment  of principal  of  or
interest   on   any  Bonds   or   to  make   any   sinking  fund   payment,  the

                                       10
<PAGE>
Trustee may withhold such notice upon  determination in good faith by the  board
of  directors,  the executive  committee or  a trust  committee of  directors or
responsible officers of the  Trustee that the withholding  of such notice is  in
the  interest of the  bondholders. (Section 4  of Article V  of the Supplemental
Indenture dated February 1, 1944 and Section 16.02 of the Restated Indenture.)

    The Company is required to file with the Trustee such information, documents
and reports with respect  to compliance by the  Company with the conditions  and
covenants  of the Indenture as  may be required by  the rules and regulations of
the Commission  including  a certificate,  furnished  not less  frequently  than
annually,  as  to  the  Company's  compliance with  all  of  the  conditions and
covenants under the  Indenture. (Section 8  of Article III  of the  Supplemental
Indenture dated February 1, 1944 and Section 8.18 of the Restated Indenture.)

GENERAL

    Whenever  all indebtedness secured thereby shall have been paid, or adequate
provision therefor made, the Trustee  shall cancel and discharge the  Indenture.
(Article XVII of the 1937 Indenture and Article XVII of the Restated Indenture.)
After  the  Effective  Date,  the  Company  may  deposit  with  the  Trustee any
combination of  cash or  Government  Obligations in  order  to provide  for  the
payment  of  any series  or all  of  the Bonds  Outstanding. The  Indenture also
provides that the Company shall furnish, to the Trustee, Officers' Certificates,
certificates of an Engineer,  Appraiser or other expert  and, in certain  cases,
Accountants'  Certificates in connection  with the authentication  of Bonds, the
release or release and substitution of  property and certain other matters,  and
Opinions  of Counsel as to the Lien  of the Indenture and certain other matters.
(Article IV of the Supplemental Indenture  dated February 1, 1944; Articles  IV,
V, VI, VII, XI and XVII and Section 20.08 of the Restated Indenture.)

                                 LEGAL OPINIONS

    Legal  opinions  relating to  the  New Bonds  will  be rendered  by  Gary R.
Johnson, 414 Nicollet Mall, Minneapolis, Minnesota, counsel for the Company, and
by Gardner, Carton & Douglas, 321 North Clark Street, Chicago, Illinois, counsel
for any underwriters, dealers or agents  named in a Prospectus Supplement.  Gary
R.  Johnson is  Vice President,  General Counsel  and Secretary  of the Company.
Matters pertaining to local laws will be passed upon by counsel for the  Company
and  as to these matters Gardner, Carton  & Douglas will rely on their opinions.
The  opinion   contained  in   this  Prospectus   under  "Description   of   New
Bonds--Security  for New  Bonds," is  the opinion  of Gary  R. Johnson. Gardner,
Carton & Douglas  has acted  from time  to time as  special counsel  for NSP  in
connection with certain matters, including the Transaction.

                                    EXPERTS

    The  financial  statements  and the  related  financial  statement schedules
incorporated in this Prospectus by reference from the Company's Annual Report on
Form  10-K  (which  reports  express  an  unqualified  opinion  and  include  an
explanatory  paragraph referring to the Company's change in method of accounting
for postretirement healthcare  costs in 1993)  have been audited  by Deloitte  &
Touche  LLP, independent public accountants, as  stated in their report included
in such Form 10-K which  is incorporated herein by  reference, and have been  so
incorporated  in reliance upon such report given upon the authority of that firm
as experts in accounting and auditing.

    The consolidated  financial statements  incorporated in  this Prospectus  by
reference  to the Annual Report on Form 10-K  of WEC for the year ended December
31, 1994 have been so incorporated in reliance on the report of Price Waterhouse
LLP, independent accountants, given on the authority of said firm as experts  in
auditing and accounting.

                              PLAN OF DISTRIBUTION

    The  Company  may sell  the  New Bonds  (i)  to or  through  underwriters or
dealers; (ii) directly to one or  more purchasers; or (iii) through agents.  The
Prospectus Supplement with respect to each series of

                                       11
<PAGE>
Offered  Bonds will set forth  the terms of the  offering of such Offered Bonds,
including the name  or names  of any underwriters,  the purchase  price of  such
Offered  Bonds and the proceeds to the  Company from such sale, any underwriting
discounts and other items  constituting underwriters' compensation, any  initial
public offering price, any discounts or concessions allowed or reallowed or paid
to  dealers and  any securities  exchanges on  which such  Offered Bonds  may be
listed. Any initial offering price and any discounts, concessions or commissions
allowed or reallowed or paid to dealers may be changed from time to time.

    If underwriters are used in the sale, the Offered Bonds will be acquired  by
the  underwriters for their own  account and may be resold  from time to time in
one or more transactions, including  negotiated transactions, at a fixed  public
offering  price or at varying prices determined at the time of sale. The Offered
Bonds may  be  offered to  the  public either  through  underwriting  syndicates
represented  by one or more managing underwriters  or directly by one or more of
such firms. The specific managing underwriter  or underwriters, if any, will  be
set  forth in the  Prospectus Supplement relating to  the Offered Bonds together
with the members  of the underwriting  syndicate, if any.  Unless otherwise  set
forth  in  the Prospectus  Supplement, the  obligations  of the  underwriters to
purchase the Offered Bonds offered thereby will be subject to certain conditions
precedent and the underwriters  will be obligated to  purchase all such  Offered
Bonds if any are purchased.

    Offered  Bonds  may  be  sold  directly by  the  Company  or  through agents
designated by the Company from time to time. The Prospectus Supplement will  set
forth  the name of any agent involved in  the offer or sale of the Offered Bonds
in respect of which the Prospectus  Supplement is delivered and any  commissions
payable by the Company to such agent.

    Any underwriters, dealers or agents participating in the distribution of the
Offered  Bonds may be deemed to be underwriters and any discounts or commissions
received by them on the sale or resale of the Offered Bonds may be deemed to  be
underwriting  discounts and commissions under the Securities Act of 1933. Agents
and underwriters  may  be  entitled,  under agreements  entered  into  with  the
Company,  to indemnification by  the Company against  certain civil liabilities,
including liabilities under the Securities Act of 1933, or to contributions with
respect to payments which the agents or underwriters may be required to make  in
respect  thereof. Agents  and underwriters  may engage  in transactions  with or
perform services for the Company in the ordinary course of business.

                                       12
<PAGE>
                                    PART II.
                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.

    Set  forth  below is  an  estimate of  the  approximate amount  of  fees and
expenses payable  by  the  Registrant (other  than  underwriting  discounts  and
commissions) in connection with the issuance of the New Bonds:

<TABLE>
<S>                                                                          <C>
Registration fee under the Securities Act of 1933..........................  $  103,449
Fees of rating agencies....................................................     100,000
Printing and engraving.....................................................      75,000
Accounting services........................................................      50,000
Trustee's charges..........................................................      50,000
Mortgage registration tax..................................................     675,000
Expenses and counsel fees for qualification or registration of the New
 Bonds under state securities laws.........................................      20,000
Miscellaneous, including traveling, telephone, copying, shipping, and other
 out-of-pocket expenses....................................................      40,000
                                                                             ----------
        Total..............................................................  $1,113,449
                                                                             ----------
                                                                             ----------
</TABLE>

    All items are estimated except the first.

ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

    Section  302A.521  of  the  Minnesota  Statutes  permits  indemnification of
officers and  directors  of  domestic  or  foreign  corporations  under  certain
circumstances  and  subject to  certain  limitations. Pursuant  to authorization
contained in the Restated  Articles of Incorporation, as  amended, Article 4  of
the  Bylaws  of  the  Company contains  provisions  for  indemnification  of its
directors and officers consistent with the provisions of Section 302A.521 of the
Minnesota Statutes.

    The Company has obtained insurance policies indemnifying the Company and the
Company's directors and officers against  certain civil liabilities and  related
expenses.

ITEM 16. EXHIBITS.

    Certain  Exhibits listed  below and marked  with an asterisk  (*) were filed
with the Securities and Exchange Commission as Exhibits to certain  Registration
Statements  under the Exhibit  number indicated after each  such Exhibit and are
incorporated  herein  by  this  reference.  These  Registration  Statements  are
identified as follows:

<TABLE>
<S>        <C>
(a)        No. 2-5290.
(b)        No. 2-5924.
(c)        No. 2-7549.
(d)        No. 2-8047.
(e)        No. 2-9631.
(f)        No. 2-12216.
(g)        No. 2-13463.
(h)        No. 2-14156.
(i)        No. 2-15220.
(j)        No. 2-18355.
(k)        No. 2-20282.
(l)        No. 2-21601.
(m)        No. 2-22476.
(n)        No. 2-26338.
(o)        No. 2-27117.
(p)        No. 2-28447.
(q)        No. 2-34250.
(r)        No. 2-36693.
(s)        No. 2-39144.
(t)        No. 2-39815.
(u)        No. 2-42598.
(v)        No. 2-46434.
(w)        No. 2-53235.
(x)        No. 2-71259.
(y)        No. 2-83364.
(z)        No. 2-97667.
</TABLE>

                                      II-1
<PAGE>

<TABLE>
<S>        <C>          <C>
Exhibit    1.01         Form of Underwriting Agreement for the New Bonds.
           *4.01A(a)    Copy  of Trust Indenture, dated February  1, 1937, from the Company to
                        Harris Trust and Savings Bank, Trustee. (B-7)
           *4.01B(a)    Copy of  Supplemental Trust  Indenture, dated  June 1,  1942, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (B-8)
           *4.01C(a)    Copy  of Supplemental Trust Indenture, dated February 1, 1944, being a
                        supplemental instrument to Exhibit 4.01A hereto. (B-9 (Revised))
           *4.01D(b)    Copy of Supplemental Trust Indenture,  dated October 1, 1945, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (7.09)
           *4.01E(c)    Copy  of Supplemental  Trust Indenture,  dated July  1, 1948,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (7.05)
           *4.01F(d)    Copy of Supplemental Trust  Indenture, dated August  1, 1949, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (7.06)
           *4.01G(e)    Copy  of Supplemental  Trust Indenture,  dated June  1, 1952,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (4.08)
           *4.01H(f)    Copy of Supplemental Trust Indenture,  dated October 1, 1954, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (4.10)
           *4.01I(g)    Copy of Supplemental Trust Indenture, dated September 1, 1956, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.09)
           *4.01J(h)    Copy  of Supplemental Trust  Indenture, dated August  1, 1957, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.10)
           *4.01K(i)    Copy of  Supplemental Trust  Indenture, dated  July 1,  1958, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (4.12)
           *4.01L(j)    Copy  of Supplemental Trust Indenture, dated December 1, 1960, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.12)
           *4.01M(k)    Copy of Supplemental Trust  Indenture, dated August  1, 1961, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (2.13)
           *4.01N(l)    Copy  of Supplemental  Trust Indenture,  dated June  1, 1962,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.14)
           *4.01O(m)    Copy of Supplemental Trust Indenture, dated September 1, 1963, being a
                        supplemental instrument to Exhibit 4.01A hereto. (4.16)
           *4.01P(n)    Copy of Supplemental Trust  Indenture, dated August  1, 1966, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (2.16)
           *4.01Q(o)    Copy  of Supplemental  Trust Indenture,  dated June  1, 1967,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.17)
           *4.01R(p)    Copy of Supplemental Trust Indenture,  dated October 1, 1967, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01R)
           *4.01S(q)    Copy  of  Supplemental Trust  Indenture, dated  May  1, 1968,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01S)
           *4.01T(r)    Copy of Supplemental Trust Indenture,  dated October 1, 1969, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01T)
           *4.01U(s)    Copy  of Supplemental Trust Indenture, dated February 1, 1971, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01U)
           *4.01V(t)    Copy of  Supplemental Trust  Indenture,  dated May  1, 1971,  being  a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01V)
</TABLE>

                                      II-2
<PAGE>
<TABLE>
<S>        <C>          <C>
Exhibit    *4.01W(u)    Copy  of Supplemental Trust Indenture, dated February 1, 1972, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01W)
           *4.01X(v)    Copy of Supplemental Trust Indenture,  dated January 1, 1973, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01X)
           *4.01Y(w)    Copy  of Supplemental Trust Indenture, dated  January 1, 1974, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01Y)
           *4.01Z(w)    Copy of Supplemental Trust Indenture, dated September 1, 1974, being a
                        supplemental instrument to Exhibit 4.01A hereto. (2.01Z)
           *4.01AA(x)   Copy of Supplemental  Trust Indenture,  dated April 1,  1975, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (4.01AA)
           *4.01BB(x)   Copy  of  Supplemental Trust  Indenture, dated  May  1, 1975,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (4.01BB)
           *4.01CC(x)   Copy of Supplemental  Trust Indenture,  dated March 1,  1976, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (4.01CC)
           *4.01DD(x)   Copy  of Supplemental  Trust Indenture,  dated June  1, 1981,  being a
                        supplemental instrument to Exhibit 4.01A hereto. (4.01DD)
           *4.01EE(y)   Copy of Supplemental Trust Indenture, dated December 1, 1981, being  a
                        supplemental instrument to Exhibit 4.01A hereto. (4.01EE)
           *4.01FF(z)   Copy  of  Supplemental Trust  Indenture, dated  May  1, 1983,  being a
                        supplemental instrument to Exhibit 4.01A hereto.
           *4.01GG(z)   Copy of Supplemental Trust Indenture, dated December 1, 1983, being  a
                        supplemental instrument to Exhibit 4.01A hereto.
           *4.01HH(z)   Copy of Supplemental Trust Indenture, dated September 1, 1984, being a
                        supplemental instrument to Exhibit 4.01A hereto.
           *4.01II(z)   Copy  of Supplemental Trust Indenture, dated December 1, 1984, being a
                        supplemental instrument to Exhibit 4.01A hereto.
           4.01JJ       Copy of  Supplemental Trust  Indenture,  dated May  1, 1985,  being  a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.36
                        to  the Company's Annual Report on Form 10-K (File No. 1-3034) for the
                        year ended December 31, 1985 and incorporated herein by reference.
           4.01KK       Copy of Supplemental Trust Indenture, dated September 1, 1985, being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.37
                        to the Company's Annual Report on Form 10-K (File No. 1-3034) for  the
                        year ended December 31, 1985, and incorporated herein by reference.
           4.01LL       Copy  of Supplemental and Restated Trust Indenture, dated May 1, 1988,
                        being a  supplemental instrument  to Exhibit  4.01A hereto,  filed  as
                        Exhibit  4.02 to  the Company's Annual  Report on Form  10-K (File No.
                        1-3034) for the year ended December 31, 1988, and incorporated  herein
                        by reference.
           4.01MM       Copy  of Supplemental  Trust Indenture,  dated July  1, 1989,  being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        July 2, 1989, and incorporated herein by reference.
           4.01NN       Copy  of Supplemental  Trust Indenture,  dated June  1, 1990,  being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        June 6, 1990, and incorporated herein by reference.
</TABLE>

                                      II-3
<PAGE>
<TABLE>
<S>        <C>          <C>
Exhibit    4.01OO       Copy  of Supplemental Trust Indenture, dated  October 1, 1992, being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        October 13, 1992, and incorporated herein by reference.
           4.01PP       Copy  of Supplemental  Trust Indenture, dated  April 1,  1993, being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        March 30, 1993, and incorporated herein by reference.
           4.01QQ       Copy  of Supplemental Trust Indenture, dated December 1, 1993, being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        December 7, 1993, and incorporated herein by reference.
           4.01RR       Copy  of Supplemental Trust Indenture, dated February 1, 1994, being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        February 10, 1994, and incorporated herein by reference.
           4.01SS       Copy  of Supplemental Trust Indenture, dated  October 1, 1994, being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        October 5, 1994, and incorporated herein by reference.
           4.01TT       Copy  of Supplemental  Trust Indenture,  dated June  1, 1995,  being a
                        supplemental instrument to Exhibit 4.01A hereto, filed as Exhibit 4.01
                        to the Company's Current  Report on Form 8-K  (File No. 1-3034)  dated
                        June 28, 1995, and incorporated herein by reference.
           4.01UU       Form  of Supplemental Trust  Indenture, for each  series of New Bonds,
                        being a supplemental instrument to Exhibit 4.01A hereto.
           5.01         Opinion of Gary R. Johnson as to legality of the New Bonds.
           12.01        NSP statement of Computation of ratios of earnings to fixed charges.
           12.02        New NSP statement of  computation of pro forma  ratios of earnings  to
                        fixed charges.
           23.01        Independent Auditor's Consent
           23.02        Consent of Legal Counsel
           23.03        Consent of Independent Certified Public Accountants
           24.01        Power of Attorney.
           25.01        Form  T-1 Statement of eligibility of Harris Trust and Savings Bank to
                        act as Trustee under the Indenture which will secure the New Bonds.
</TABLE>

ITEM 17.  UNDERTAKINGS.

    The undersigned registrant hereby undertakes:

        (1) To file, during any period in which offers or sales are being  made,
    a  post-effective amendment to  this registration statement:  (i) to include
    any prospectus required by section 10(a)(3)  of the Securities Act of  1933;
    (ii)  to reflect  in the  prospectus any facts  or events  arising after the
    effective  date  of   the  registration  statement   (or  the  most   recent
    post-effective  amendment thereof) which, individually  or in the aggregate,
    represent  a  fundamental  change  in  the  information  set  forth  in  the
    registration  statement.  Notwithstanding  the  foregoing,  any  increase or
    decrease in  volume of  securities offered  (if the  total dollar  value  of
    securities  offered  would not  exceed that  which  was registered)  and any
    deviation from the low or high  end of the estimated maximum offering  range
    may  be  reflected  in the  form  of  prospectus filed  with  the Commission
    pursuant to Rule 424(b) if, in

                                      II-4
<PAGE>
    the aggregate, the changes  in volume and price  represented no more than  a
    20%  change  in  the  maximum  aggregate offering  price  set  forth  in the
    "Calculation of  Registration  Fee"  table  in  the  effective  registration
    statement; and (iii) to include any material information with respect to the
    plan  of distribution not previously disclosed in the registration statement
    or any material change  to such information  in the registration  statement;
    provided,  however, that  clauses (i)  and (ii)  above do  not apply  if the
    registration statement  is on  Form  S-3 or  Form  S-8 and  the  information
    required  to be included  in a post-effective amendment  by those clauses is
    contained in periodic reports filed 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.

        (2)  That,  for  the  purpose of  determining  any  liability  under the
    Securities Act of 1933, each  such post-effective amendment shall be  deemed
    to  be  a  new registration  statement  relating to  the  securities offered
    therein, and the offering of such securities at that time shall be deemed to
    be the initial bona fide offering thereof.

        (3) To remove from registration  by means of a post-effective  amendment
    any   of  the  securities  being  registered  which  remain  unsold  at  the
    termination of the offering.

    The  undersigned  registrant  hereby   undertakes  that,  for  purposes   of
determining  any liability under the Securities Act  of 1933, each filing of the
registrant's annual report  pursuant to section  13(a) or section  15(d) of  the
Securities  Exchange  Act  of 1934  (and  where  applicable, each  filing  of an
employee  benefit  plan's  annual  report  pursuant  to  section  15(d)  of  the
Securities  Exchange  Act of  1934)  that is  incorporated  by reference  in the
registration statement  shall  be deemed  to  be a  new  registration  statement
relating  to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

    Insofar as indemnification for liabilities arising under the Securities  Act
of  1933 may be permitted to directors,  officers and controlling persons of the
registrant pursuant  to the  foregoing provisions  described under  Item 15,  or
otherwise, the registrant has been advised that in the opinion of the Securities
and  Exchange  Commission  such  indemnification  is  against  public  policy as
expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than  the
payment by the registrant of expenses incurred or paid by a director, officer or
controlling  person of the  registrant in the successful  defense of any action,
suit or proceeding) is asserted by such director, officer or controlling  person
in  connection with the securities being registered, the registrant will, unless
in the  opinion  of its  counsel  the matter  has  been settled  by  controlling
precedent,  submit to a  court of appropriate  jurisdiction the question whether
such indemnification  by  it  is  against public  policy  as  expressed  in  the
Securities  Act of 1933 and  will be governed by  the final adjudication of such
issue.

                                      II-5
<PAGE>
                                   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  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 6TH  DAY
OF OCTOBER 1995.

                                          NORTHERN STATES POWER COMPANY

                                          By Arland D. Brusven, Vice President
                                          -- Finance

    PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, AS AMENDED, THIS
REGISTRATION  STATEMENT HAS  BEEN SIGNED BELOW  BY THE FOLLOWING  PERSONS IN THE
CAPACITIES AND ON THE DATES INDICATED.

<TABLE>
<CAPTION>
                    SIGNATURE                        TITLE                        DATE
<S>        <C>                          <C>                               <C>
- ----------------------------------------------------------------------------------------------

           James J. Howard              Principal Executive Officer
                                          and Director

           Edward J. McIntyre           Principal Financial Officer

           Roger D. Sandeen             Principal Accounting Officer

           H. Lyman Bretting            Director

           David A. Christensen         Director

           W. John Driscoll             Director

           Dale L. Haakenstad           Director

           Allen F. Jacobson            Director

           Richard M. Kovacevich        Director

           Douglas W. Leatherdale       Director

           John E. Pearson              Director

           G. M. Pieschel               Director

           Margaret R. Preska           Director

           A. Patricia Sampson          Director

           Edwin M. Theisen             Director

                                                                          October 6, 1995
                           By Arland D. Brusven (attorney-in-fact)
</TABLE>

                                      II-6
<PAGE>
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
   METHOD OF
    FILING       EXHIBIT NO.                                          DESCRIPTION
- ---------------  ------------  ------------------------------------------------------------------------------------------
<S>              <C>           <C>
          DT          1.01     Form of Underwriting Agreement for the New Bonds.

          DT          4.01UU   Form  of Supplemental Trust Indenture, for each  series of New Bonds, being a supplemental
                                instrument to Exhibit 4.01A hereto.

          DT          5.01     Opinion of Gary R. Johnson as to legality of the New Bonds.

          DT         12.01     NSP statement of Computation of ratio of earnings to fixed charges.

          DT         12.02     New NSP statement of computation of pro forma ratios of earnings to fixed charges.

          DT         23.01     Independent Auditor's Consent

          DT         23.02     Consent of Legal Counsel

          DT         23.03     Consent of Independent Certified Public Accountants

          DT         24.01     Power of Attorney.

          DT         25.01     Form T-1 Statement of eligibility of Harris Trust and Savings Bank to act as Trustee under
                                the Indenture which will secure the New Bonds.
</TABLE>

DT -- Filed electronically with this direct transmission.
