Exhibit 99.2


                       MidAmerican Energy Holdings Company
                           666 Grand Avenue, Suite 500
                             Des Moines, Iowa 50309





October 1, 2008

Charles Berardesco
Vice President and Deputy General Counsel
Constellation Energy Group, Inc.
750 E. Pratt Street
Baltimore, Maryland  21202

Re:   Waiver of Limited Due Diligence Termination Right
      -------------------------------------------------

Dear Charles:

Reference is hereby made to that certain Agreement and Plan of Merger, dated as
of September 19, 2008 (the "Merger Agreement"), by and among Constellation
Energy Group, Inc., a Maryland corporation (the "Company"), MidAmerican Energy
Holdings Company, an Iowa corporation (the "Parent"), and MEHC Merger Sub Inc.,
a Maryland corporation and a wholly owned subsidiary of Parent (the "Merger
Sub"). Capitalized terms used but not defined herein shall have the meaning
ascribed to such terms in the Merger Agreement.

Parent hereby waives the right to terminate the Merger Agreement pursuant to
Section 9.1(h) thereof. This waiver is limited in scope and shall not be deemed
to waive, modify or amend any rights or obligations of the Company, Parent or
Merger Sub under or pursuant to the Merger Agreement, including Parent's right
to exercise the Limited Due Diligence Termination Right (as modified pursuant to
Section 8.2(k) of the Merger Agreement) in determining whether the closing
condition contained in Section 8.2(k) of the Merger Agreement is satisfied at
the Closing.

This letter shall be governed by and construed in accordance with the laws of
the State of Maryland, without regard to conflicts of laws principles thereof.

                            [Signature Page Follows]






Please confirm our understanding regarding the matters set forth herein by
countersigning this letter and returning a copy to us.

                                Very truly yours,

                              MIDAMERICAN ENERGY HOLDINGS COMPANY


                              By: /s/ Gregory E. Abel
                                  ----------------------------------------------
                                  Name:   Gregory E. Abel
                                  Title:  President and Chief Executive Officer



Accepted and Agreed as of October 1, 2008:

CONSTELLATION ENERGY GROUP, INC.


By:  /s/ Charles Berardesco
     --------------------------------------------------
      Name:   Charles Berardesco
      Title:  Vice President and Deputy General Counsel



cc:  Mayo A. Shattuck III
     George Stamas
     Mark Director
     Doug Anderson
     Peter Hanlon