<PAGE>

                                                                   Exhibit 4.1

              THIRD AMENDMENT TO LG&E ENERGY CORP. RIGHTS AGREEMENT
              -----------------------------------------------------

                  THIRD AMENDMENT, dated as of February 27, 2000 (the
"Amendment"), to the Rights Agreement, dated as of December 5, 1990, as
heretofore amended by the First Amendment thereto, dated as of June 7, 1995,
and the Second Amendment thereto, dated as of May 20, 1997 (as so amended,
the "Rights Agreement"), between LG&E ENERGY CORP., a Kentucky corporation
(the "Company"), and LOUISVILLE GAS AND ELECTRIC COMPANY, a Kentucky
corporation, as Rights Agent (the "Rights Agent").

                                   WITNESSETH

                  WHEREAS, on December 5, 1990, the Board of Directors of the
Company declared a dividend distribution of one Right for each share of
Common Stock outstanding at the close of business on the Record Date, each
Right representing the right to purchase one one-hundredth of a share of
Preferred Stock upon the terms and conditions set forth in the Rights
Agreement; and

                  WHEREAS, the Rights remain issued and outstanding and the
Rights Agreement remains in effect with respect thereto; and

                  WHEREAS, no Distribution Date has occurred; and

                  WHEREAS, the Company, PowerGen plc, an English public
limited company ("PowerGen"), a Delaware corporation to be formed as an
indirect wholly-owned subsidiary of PowerGen ("US Subholdco 2") and a
Kentucky corporation to be formed as a wholly-owned subsidiary of PowerGen
("Merger Sub"), propose to enter into an Agreement and Plan of Merger (the
"Merger Agreement"), pursuant to which Merger Sub would merge with and into
the Company ("the Merger") with the Company surviving the Merger; and

                  WHEREAS, in connection with the anticipated approval,
execution, and delivery of the Merger Agreement, the Board of Directors of
the Company has approved, in accordance with Section 26 of the Rights
Agreement, this Amendment and has directed the appropriate officers of the
Company to take all appropriate steps to execute this Amendment and deliver
it to the Rights Agent.

                  NOW, THEREFORE, in consideration of the premises and mutual
agreements herein set forth, the parties hereby agree as follows:

                  (1)  AMENDMENT TO SUBSECTION 1(a).

                  Subsection 1(a) of the Rights Agreement is hereby deleted and
restated to read in its entirety as follows:

                                       1

<PAGE>

               (a) "Acquiring Person" shall mean any Person who or which,
          together with all Affiliates and Associates of such Person, shall be
          the Beneficial Owner of 15% or more of the outstanding Common Stock
          (other than as a result of a Permitted Offer) or who or which was such
          a Beneficial Owner at any time after December 5, 1990, whether or not
          such Person continues to be the Beneficial Owner of securities
          representing 15% or more of the Common Stock, provided, however, that
          the term "Acquiring Person" shall not include:

                    (i) an Exempt Person; or

                    (ii) PowerGen, its subsidiaries or any Affiliate or
               Associate of PowerGen, as a result of their acquisition of
               Beneficial Ownership of shares of Common Stock by reason of the
               approval, execution or delivery of the PowerGen Merger Agreement,
               or by reason of the consummation of the Merger or any transaction
               contemplated by Section 6.24 of the PowerGen Merger Agreement, so
               long as neither PowerGen nor any of its subsidiaries is the
               Beneficial Owner of any shares of Common Stock other than shares
               of Common Stock of which PowerGen or any of its subsidiaries is
               or becomes the Beneficial Owner by reason of the approval,
               execution, or delivery of the PowerGen Merger Agreement, or by
               reason of the consummation of the Merger or any transaction
               contemplated by Section 6.24 of the PowerGen Merger Agreement.

               Notwithstanding the foregoing, if the Board of Directors of the
          Company determines in good faith that a Person who would otherwise be
          an "Acquiring Person", has become such inadvertently and without any
          intention of changing or influencing control of the Company, and such
          Person, as promptly as practicable after being advised of such
          determination, divests himself or itself of Beneficial Ownership of a
          sufficient number of shares of Common Stock so that such Person would
          no longer be an "Acquiring Person", then such Person shall not be
          deemed to be an "Acquiring Person" for any purposes of this Agreement.

          (2) AMENDMENT TO SUBSECTION 1(mm).

          Subsection 1(mm) of the Rights Agreement is hereby amended and
     restated, to read as follows:

               "(mm) "PowerGen" shall mean PowerGen plc, an English corporation,
          and its successors."

               (3) AMENDMENT TO SUBSECTION 1(nn).

               Subsection 1(nn) of the Rights Agreement is hereby amended and
          restated, to read as follows:

                                        2

<PAGE>

               "(nn) "PowerGen Merger Agreement" shall mean the Agreement and
          Plan of Merger, dated as of February 27, 2000, by and among the
          Company, a Delaware corporation to be formed as an indirect wholly
          owned subsidiary of PowerGen, a Kentucky corporation to be formed as a
          wholly-owned subsidiary of PowerGen, and PowerGen, as the same may be
          amended from time to time."

          (4) DELETION OF SUBSECTIONS 1(oo) and 1(pp).

          Subsections 1(oo) and 1(pp) shall each be deleted in their entirety.

          (5) AMENDMENT TO SUBSECTION 3(d). Subsection 3(d) of the Rights
Agreement is hereby amended by deleting "June 7, 1995 and the Second
Amendment dated as of May 20, 1997" in the first sentence of the legend
contained therein and inserting in lieu thereof "June 7, 1995, the Second
Amendment dated as of May 20, 1997, and the Third Amendment dated as of
February 27, 2000".

          (6) AMENDMENT TO SUBSECTION 7(a). Subsection 7(a) is hereby amended by
deleting "the close of business on December 19, 2000" and substituting in
lieu thereof "on the date of the consummation of the Merger contemplated by
the PowerGen Merger Agreement, provided, however that if the PowerGen
Merger Agreement is terminated prior to December 19, 2000, then the rights
shall expire on December 19, 2000, and if the PowerGen Merger Agreement is
terminated on or after December 19, 2000, then the rights shall expire 5
business days after the date of such termination."

          (7) ADDITION OF SECTION 35.

          A new Section 35 of the Rights Agreement is added, to read as follows:

               "Section 35. MERGER WITH POWERGEN. For the avoidance of doubt,
          notwithstanding any provision herein to the contrary, (a) neither
          PowerGen, US Subholdco 2, Merger Sub nor any of their respective
          Affiliates or Associates shall be considered an Acquiring Person under
          this Rights Agreement and (b) no Distribution Date, Stock Acquisition
          Date or Triggering Event shall occur, and the Rights will not separate
          from the shares of Common Stock or become exercisable pursuant to any
          other provision hereof, solely as a result of the approval, execution,
          or delivery of the PowerGen Merger Agreement and/or the other
          transactions contemplated thereby."

          (8) AMENDMENT OF EXHIBIT B. The Form of Right Certificate attached as
Exhibit B to the Rights Agreement is hereby amended by (i) deleting
"December 19, 2000" in the first line of the legend contained therein and
inserting in lieu thereof "the Final Expiration Date (as defined in the
Rights Agreement, as amended as of the date hereof)"; (ii) deleting "June
7, 1995 and the Second Amendment dated as of May 20, 1997" in the first
sentence of the first paragraph thereof and inserting in lieu thereof "June
7, 1995, the Second Amendment dated as of May 20,

                                        3

<PAGE>


1997, and the Third Amendment dated as of February 27, 2000"; and (iii) deleting
"December 19, 2000" in the first sentence of the first paragraph thereof and
inserting in lieu thereof "the Final Expiration Date (as defined in the Rights
Agreement, as amended)".

          (9) EFFECTIVENESS. This Amendment shall be deemed to be in force and
effective immediately prior to the execution and delivery of the Merger
Agreement. Except as amended hereby, the Rights Agreement shall remain in
full force and effect and shall be otherwise unaffected hereby.

          (10) DEFINED TERMS. Unless otherwise defined herein, all defined terms
used herein shall have the same meanings given to them in the Rights
Agreement.

          (11) GOVERNING LAW. This Amendment shall be deemed to be a contract
made under the laws of the Commonwealth of Kentucky and for all purposes
shall be governed by and construed in accordance with the laws of such
Commonwealth applicable to contracts to be made and performed entirely
within such Commonwealth.

          (12) COUNTERPARTS. This Amendment may be executed in any number of
counterparts, each of which shall for all purposes be deemed an original
and all of which shall together constitute but one and the same instrument.

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed as of the day and year first above written.

                                LG&E ENERGY CORP.

                                By: /s/ R. Foster Duncan
                                    ------------------------
                                    Name:  R. Foster Duncan
                                    Title: Executive Vice President and
                                           Chief Financial Officer

                                LOUISVILLE GAS AND ELECTRIC COMPANY, as
                                Rights Agent

                                By: /s/  John R. McCall
                                    -------------------------
                                    Name:  John R. McCall
                                    Title: Executive Vice President,
                                           General Counsel and Corporate
                                           Secretary

                                        4