Offer of Cash Purchase of Outstanding Stocks – Icahn Enterprises

Offer to Purchase for Cash

All Outstanding Shares of Common Stock

Including the Associated Rights

of

DYNEGY INC.

by

IEH MERGER SUB LLC

a wholly-owned subsidiary of

ICAHN ENTERPRISES HOLDINGS L.P.

THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON JANUARY 25, 2011, UNLESS THE OFFER IS EXTENDED (SUCH DATE AND TIME, AS IT MAY BE EXTENDED, THE “EXPIRATION DATE“) OR EARLIER TERMINATED.

December 22, 2010

To Brokers, Dealers, Commercial Banks,

Trust Companies and Other Nominees:

We have been appointed by IEH Merger Sub LLC, a Delaware limited liability
company (the “Offeror“) and a wholly-owned subsidiary of Icahn
Enterprises Holdings L.P., a Delaware limited partnership, to act as Information
Agent in connection with the Offeror153s offer to purchase all of the issued and
outstanding shares of common stock, par value $.01 per share (the “Common
Stock“), of Dynegy Inc., a Delaware corporation (the “Company“), and
the associated rights issued pursuant to the Stockholder Protection Rights
Agreement, dated as of November 22, 2010, and as amended on December 15, 2010,
between the Company and Mellon Investor Services LLC, as Rights Agent, that are
issued and outstanding (the “Rights” and, together with the Common Stock,
the “Shares“), at a price of $5.50 per Share, net to the seller in cash
without interest, less any applicable withholding taxes, upon the terms and
subject to the conditions set forth in the Offer to Purchase dated December 22,
2010 (the “Offer to Purchase“), and the related Letter of Transmittal
(which, together with any amendments or supplements thereto, collectively
constitute the “Offer“), copies of which are enclosed herewith.

Consummation of the Offer is subject to certain conditions as described in
the Offer to Purchase. See Section 15 of the Offer to Purchase. Subject to the
terms and conditions specified in the Offer, which conditions (other than the
Minimum Condition and the Regulatory Condition (in each case, as defined below),
which may only be waived with the prior written consent of the Company) may be
waived by the Offeror at any time in whole or in part, the Offeror will accept
for payment any and all Shares validly tendered and not properly withdrawn on or
prior to the expiration date of the Offer.

Please furnish copies of the enclosed materials to those of your clients for
whose accounts you hold Shares registered in your name or in the name of your
nominee.

For your information and for forwarding to your clients, we are enclosing the
following documents:

1. The Offer to Purchase.

2. The Letter of Transmittal for your use in accepting the Offer and for the
information of your clients, including a Certification of Taxpayer
Identification Number on Substitute Form W-9. Facsimile copies of the Letter of
Transmittal (with manual signatures) may be used to tender Shares.

3. A printed form of letter that may be sent to your clients for whose
account you hold Shares in your name or in the name of your nominee with space
provided for obtaining such clients153 instructions with regard to the Offer.

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4. A Notice of Guaranteed Delivery to be used to accept the Offer if
certificates representing Shares and, if certificates have been issued in
respect of the Rights prior to the expiration of the Offer, certificates
representing the associated Rights are not immediately available or if time will
not permit all required documents to reach American Stock Transfer & Trust
Company (the “Depositary“) prior to the expiration date of the Offer or
if the procedures for book-entry transfer cannot be completed on a timely basis.

5. Guidelines of the Internal Revenue Service for Certification of Taxpayer
Identification Number on Substitute Form W-9. Stockholders who fail to complete
and sign the Substitute Form W-9 may be subject to a required federal backup
withholding tax on the gross proceeds payable to such stockholder or other payee
pursuant to the Offer. See Section 2 of the Offer to Purchase.

6. A return envelope addressed to the Depositary.

Your attention is directed to the following:

1. The tender price is $5.50 per Share, net to the seller in cash, without
interest, less any applicable withholding taxes, upon the terms and subject to
the conditions set forth in the Offer to Purchase.

2. The Offer is being made for all Shares.

3. The Offer and withdrawal rights will expire at 12:00 midnight, New York
City time, on January 25, 2011, unless the Offer is extended or earlier
terminated.

4. The Offer is being made in connection with the Agreement and Plan of
Merger, dated as of December 15, 2010 (as it may be amended from time to time,
the “Merger Agreement“), by and among the Company, the Offeror, and IEP
Merger Sub Inc., a Delaware corporation and a wholly-owned subsidiary of the
Offeror (“Merger Sub“), pursuant to which, after completion of the Offer
and the satisfaction or waiver of the conditions set forth therein, Merger Sub
will be merged with and into the Company, and the Company will be the surviving
corporation (which we refer to as the “Merger“).

5. The Board of Directors of the Company, acting upon the recommendation of a
special committee of the Board of Directors of the Company consisting only of
independent directors of the Company, has, upon the terms and subject to the
conditions set forth in the Merger Agreement, unanimously (i) determined that
the Offer and the Merger are fair to, and in the best interests of, the Company
and its stockholders, (ii) approved and declared advisable the Merger Agreement,
the Offer, the Merger and the other transactions contemplated thereby, and (iii)
recommended that the Company153s stockholders accept the Offer, tender their
Shares into the Offer and, if required by applicable law, adopt the Merger
Agreement.

6. The Offer is conditioned on there being validly tendered in the Offer and
not properly withdrawn prior to midnight, New York City time, on January 25,
2011 (the “Expiration Date,” unless the Offeror shall have extended the period
during which the Offer is open pursuant to and in accordance with the Merger
Agreement, in which event “Expiration Date” shall mean the latest time and date
at which the Offer, as so extended by the Offeror, shall expire) that number of
Shares which, when added to any Shares already owned by the Offeror, its
subsidiaries and certain affiliates of the Offeror that are parties to the
Stockholder Support Agreement entered into simultaneously with the Merger
Agreement between such parties and the Company (including Shares that are
subject to options to purchase Shares to the extent such options have been
irrevocably exercised and paid for prior to the Expiration Date), represents at
least a majority of the issued and outstanding Shares on a fully diluted basis
as of the Expiration Date (assuming the issuance of all Shares that may be
issued upon the vesting of outstanding restricted stock of the Company, plus
Shares issuable upon the exercise of all outstanding options to purchase Shares
under Company stock plans, warrants and other rights to purchase Shares with an
exercise price per Share less

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than the Offer Price) (such condition, the “Minimum Condition“). The
Offer is also subject to the satisfaction, prior to the Expiration Date, of
certain other conditions set forth in the Offer to Purchase, including, among
other conditions, that (i) the Merger Agreement shall not have been terminated
in accordance with its terms, (ii) the approval of the Federal Energy Regulatory
Commission under Section 203 of the Federal Power Act, as amended, shall have
been received and the approval, or a determination that no approval is required,
of the New York State Public Service Commission under the New York Public
Service Law, as amended, shall have been received with respect to the
consummation of the Offer and the Merger, and (iii) the waiting period
applicable to the consummation of the Offer under the Hart-Scott-Rodino
Antitrust Improvements Act of 1976, as amended, and the rules and regulations
thereunder shall have expired or been terminated (the conditions set forth in
clauses (ii) and (iii) above, the “Regulatory Condition“). The Offer is
also subject to other specified conditions. See Section 15 of the Offer to
Purchase.

7. Stockholders who tender Shares will not be obligated to pay brokerage fees
or commissions to the Information Agent or the Depositary or, except as set
forth in Instruction 6 of the Letter of Transmittal, stock transfer taxes on the
purchase of Shares by Offeror pursuant to the Offer.

Upon the terms and subject to the conditions of the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), the Offeror will accept for payment and pay for all Shares that are
validly tendered on or prior to the Expiration Date and not theretofore properly
withdrawn pursuant to the Offer. In all cases, payment for Shares accepted for
payment pursuant to the Offer will be made only after (a) timely receipt by the
Depositary of (i) certificates representing such Shares and, if certificates
have been issued in respect of the Rights prior to the expiration of the Offer,
certificates representing the associated Rights (or a timely confirmation of a
book-entry transfer of such Shares into the Depositary153s account at The
Depository Trust Company, pursuant to the procedures described in Section 2 of
the Offer to Purchase), (ii) a properly completed and duly executed Letter of
Transmittal (or facsimile thereof) with any required signature guarantees (or,
in connection with a book-entry transfer, an Agent153s Message (as defined in
Section 2 of the Offer to Purchase)), and (iii) all other documents required by
the Letter of Transmittal, or (b) compliance with the guaranteed delivery
procedures specified under Section 2 of the Offer to Purchase.

The Rights are presently evidenced by the certificates for the Common Stock.
However, in the future the Company may issue separate certificates representing
the Rights. Until such time as any such certificates are issued, a tender by a
stockholder of such stockholder153s shares of Common Stock will also constitute a
tender of the associated Rights. After such time as any such certificates
representing Rights are issued, a stockholder will also be required to tender
such certificates representing the associated Rights in connection with a tender
by such stockholder of such stockholder153s shares of Common Stock. Unless the
context requires otherwise, all references in this letter of transmittal to
“Shares” shall include the associated Rights.

If holders of Shares wish to tender, but it is impracticable for them to
forward their certificates or other required documents prior to the expiration
of the Offer, a tender may be effected by following the guaranteed delivery
procedures specified under Section 2 of the Offer to Purchase.

The Offeror will not pay any fees or commissions to any broker or dealer or
to any other person (other than the Depositary and the Information Agent) in
connection with the solicitation of tenders of Shares pursuant to the Offer. The
Offeror will, however, upon request, reimburse you for customary mailing and
handling expenses incurred by you in forwarding the enclosed materials to your
clients. The Offeror will pay or cause to be paid any stock transfer taxes
payable on the transfer of Shares to it, except as otherwise provided in
Instruction 6 of the Letter of Transmittal.

YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS
AS PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON JANUARY 25, 2011, UNLESS THE
OFFER IS EXTENDED.

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Any inquiries you may have with respect to the Offer should be directed to,
and additional copies of the enclosed materials may be obtained by contacting,
the undersigned at (203) 658-9400.

Very truly yours,

MORROW & Co., LLC

NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL
CONSTITUTE YOU OR ANY PERSON AS AN AGENT OF OFFEROR OR THE COMPANY, THE
DEPOSITARY OR THE INFORMATION AGENT, OR ANY AFFILIATE OF ANY OF THE FOREGOING,
OR AUTHORIZE YOU OR ANY OTHER PERSON TO GIVE ANY INFORMATION OR USE ANY DOCUMENT
OR MAKE ANY STATEMENTS ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE OFFER
OTHER THAN THE DOCUMENTS ENCLOSED HEREWITH AND THE STATEMENTS CONTAINED THEREIN.

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