Third Supplemental Indenture

THIRD SUPPLEMENTAL INDENTURE, dated as of October 1, 2004 (herein called the " Third Supplemental Indenture "), between MIDAMERICAN ENERGY COMPANY, a corporation duly organized and existing under the laws of the State of Iowa (herein called the " Company "), and THE BANK OF NEW YORK, a New York banking association duly organized and existing under the laws of the United States of America, as Trustee (herein called the " Trustee "), under the Original Indenture referred to below.

WHEREAS, the Company has heretofore executed and delivered to the Trustee an indenture dated as of February 8, 2002, as amended (herein called the " Original Indenture "), as supplemented by the First Supplemental Indenture dated as of February 8, 2002 and the Second Supplemental Indenture dated as of January 14, 2003, to provide for the issuance from time to time of its unsubordinated debentures, notes or other evidences of indebtedness, the form and terms of which are to be established as set forth in Sections 2.01 and 3.01 of the Original Indenture;

WHEREAS, Section 9.01 of the Original Indenture provides, among other things, that the Company and the Trustee may enter into indentures supplemental to the Original Indenture for, among other things, (i) the purpose of establishing the form and terms of the Securities (as defined in the Original Indenture) of any series as permitted by Sections 2.01 and 3.01 of the Original Indenture, and (ii) to add to the covenants of the Company for the benefit of the Holders of all or any series of Securities (as defined in the Original Indenture);

WHEREAS, the Company desires to create one series of securities to be designated the "4.650% Notes due 2014" and all action on the part of the Company necessary to authorize the issuance of up to three hundred fifty million dollars ($350,000,000) aggregate principal amount of such securities (the " Securities ") under the Original Indenture and this Third Supplemental Indenture has been duly taken;

WHEREAS, the Company and the Trustee desire to make certain amendments to the Original Indenture in conformance with the requirements described above; and

WHEREAS, all acts and things necessary to make the Securities, when executed by the Company and authenticated and delivered by the Trustee as provided in the Original Indenture, the valid and binding obligations of the Company and to constitute these presents a valid and binding supplemental indenture and agreement according to its terms, have been done and performed.

NOW, THEREFORE, THIS THIRD SUPPLEMENTAL INDENTURE WITNESSETH:

That in consideration of the premises and of the acceptance and purchase of the Securities by the holders thereof and of the acceptance of this trust by the Trustee, the Company covenants and agrees with the Trustee, for the equal benefit of holders of the Securities, as follows:

Unless otherwise defined herein, the use of the terms and expressions herein is in accordance with the definitions, uses and constructions contained in the Original Indenture and the form of Security attached hereto as Exhibit A .

Section 2.01. Issue of Securities. One series of notes, which shall be designated the "4.650% Notes due 2014", shall be executed, authenticated and delivered in accordance with the provisions of, and shall in all respects be subject to, the terms, conditions and covenants of the Original Indenture and this Third Supplemental Indenture (including the form of Security set forth in Exhibit A ).

Section 2.02. Optional Redemption. The Securities may be redeemed, in whole or in part, at the option of the Company pursuant to the terms set forth in Annex 1 to the Securities to be redeemed. The provisions of Article XI of the Original Indenture shall also apply to any optional redemption of Securities by the Company.

Section 2.03. Defeasance and Discharge. The provisions of Section 14.02 of the Original Indenture shall be applicable to the Securities.

Section 2.04. Covenant Defeasance. The provisions of Section 14.03 of the Original Indenture shall be applicable to the Securities.

Section 2.05. Place of Payment. The Place of Payment in respect of the Securities will be in The City of New York, initially at the Corporate Trust Office of The Bank of New York (which as of the date hereof is located at 101 Barclay Street, 8 West, New York, New York 10286, Attention: Corporate Trust Administration).

Section 2.06. Form of Securities; Incorporation of Terms. The form of the Securities shall be substantially in the form of Exhibit A , the terms of which are herein incorporated by reference and which are part of this Third Supplemental Indenture. The Securities shall be issued as one or more Global Securities in fully registered form, as determined in accordance with Section 2.01 of the Original Indenture. The Global Securities shall be delivered by the Trustee to the Depositary, as the Holder thereof, or a nominee or custodian therefore, to be held by the Depositary in accordance with the Original Indenture.

Section 2.07. Exchange of the Global Securities. Each of the Global Securities shall be exchangeable for definitive Securities only as provided in Section 3.05 of the Original Indenture.

Section 2.08. Regular Record Date for the Securities. The Regular Record Date for the Securities shall be the March 15 or September 15 immediately prior to each Interest Payment Date.

Section 2.09. Authorized Denominations. Beneficial interests in Global Securities, as well as definitive Securities, may be held only in denominations of $1,000 and integral multiples of $1,000 in excess thereof.

Section 2.10. Additional Securities. The Company may from time to time, without the consent of the Holders of the Securities, create and issue further securities having the same terms and conditions as the Securities in all respects, except for the original issue date and offering price. Additional Securities issued in this manner will be consolidated with, and form a single series with, the Securities and shall thereafter be deemed Securities for all purposes.

Section 3.01. Depositary. The Depositary Trust Company, its nominees and their respective successors are hereby appointed Depositary with respect to the Global Securities.

Section 4.01. Amendments. The Original Indenture is hereby amended as follows:

(a)   Section 1.01 of the Original Indenture is hereby amended to add or modify the following definitions, as the case may be:

" 'Common Shareholders Equity ' means, at any time, the total shareholders' equity of the Company and its consolidated subsidiaries, determined on a consolidated basis in accordance with generally accepted accounting principles, as of the end of the most recently completed fiscal quarter of the Company for which financial information is then available."

"' Midwest Power Indenture ' means the General Mortgage Indenture and Deed of Trust, dated as of January 1, 1993, between Midwest Power Systems Inc. and Morgan Guaranty Trust Company of New York, trustee (Harris Trust and Savings Bank, successor trustee), and indentures supplemental thereto."

"' Permitted Encumbrances ' means:

(a)   (i) any mortgage, pledge or other lien or encumbrance on any property hereafter acquired or constructed by the Company or a Subsidiary, or on which property so constructed is located, and created prior to, contemporaneously with or within 360 days after, such acquisition or construction or the commencement of commercial operation of such property to secure or provide for the payment of any part of the purchase or construction price of such property, or (ii) any property subject to any mortgage, pledge, or other lien or encumbrance upon such property existing at the time of acquisition thereof by the Company or any Subsidiary, whether or not assumed by the Company or such Subsidiary, or (iii) any mortgage, pledge or other lien or encumbrance existing on the property, shares of stock, membership interests or indebtedness of a corporation or limited liability company at the time such corporation or limited liability company shall