<PAGE>



                  FACE OF SENIOR SECURED EXCHANGE NOTE DUE 2009

         THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE
HEREINAFTER REFERRED TO AND IS HELD BY THE DEPOSITORY TRUST COMPANY (THE
"DEPOSITARY") OR A NOMINEE OF THE DEPOSITARY. THIS SECURITY IS EXCHANGEABLE FOR
SECURITIES HELD BY A PERSON OTHER THAN THE DEPOSITARY OR ITS NOMINEE ONLY IN THE
LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER OF THIS
SECURITY (OTHER THAN A TRANSFER OF THIS SECURITY AS A WHOLE BY THE DEPOSITARY TO
A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY
OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO
A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH SUCCESSOR DEPOSITARY) MAY BE MADE
EXCEPT IN LIMITED CIRCUMSTANCES.

         UNLESS THIS GLOBAL SECURITY IS PRESENTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITARY TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF
TRANSFER, EXCHANGE OR PAYMENT, AND ANY DEFINITIVE SECURITY IS ISSUED IN THE NAME
OF CEDE & CO. OR SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE
OF THE DEPOSITARY (AND ANY PAYMENT IS MADE TO CEDE & CO., OR TO SUCH OTHER
ENTITY AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY), ANY
TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON
IS WRONGFUL IN AS MUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN
INTEREST HEREIN.


<PAGE>




                            MIDAMERICAN FUNDING, LLC
                      6.339% Senior Secured Notes due 2009

No. 1                                                     $175,000,000

                                                          CUSIP No. 59562H AH 1

         MIDAMERICAN FUNDING, LLC., a limited liability company organized under
the laws of Iowa (herein called the "Company," which term includes any successor
corporation or limited liability company under the Indenture hereinafter
referred to), for value received, hereby promises to pay to CEDE & CO., or
registered assigns, the principal amount of One Hundred Seventy-Five Million
Dollars (such principal amount, as it may from time to time be adjusted by
endorsement on Schedule A hereto, is hereinafter referred to as the "Principal
Amount") on March 1, 2009, and to pay interest thereon from March 1, 2000, or
from the most recent Interest Payment Date to which interest has been paid or
duly provided for, semi-annually on March 1 and September 1 in each year,
commencing September 1, 2000, at the rate of 6.339% per annum, until the
Principal Amount hereof is paid or made available for payment; provided that any
Principal Amount and premium, and any such installment of interest, which is
overdue shall continue to bear interest at the aforesaid rate of 6.339% per
annum (to the extent that the payment of such interest shall be legally
enforceable) from the dates such amounts are due until they are paid or made
available for payment. The interest so payable, and punctually paid or duly
provided for, on any Interest Payment Date will, as provided in such Indenture,
be paid to the Person in whose name this Security (or one or more Predecessor
Securities) is registered at the close of business on the Regular Record Date
for such interest, which shall be the February 15 or August 15 (whether or not a
Business Day), as the case may be, immediately preceding such Interest Payment
Date. Any such interest not so punctually paid or duly provided for will
forthwith cease to be payable to the Person in whose name this Security (or one
or more Predecessor Securities) is registered on such Regular Record Date and
may be paid to the Person in whose name this Security (or one or more
Predecessor Securities) is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee, notice whereof shall be given to Holders of Securities of this series
not less than 10 days prior to such Special Record Date, or be paid at any time
in any other lawful manner not inconsistent with the requirements of any
securities exchange on which the Securities of this series may be listed, and
upon such notice as may be required by such exchange, all as more fully provided
in said Indenture.

         Payment of the principal of (and premium, if any) and interest on this
Security shall be made at the office or agency of the Company maintained for
that purpose in the Borough of Manhattan, The City of New York, or at such
additional offices or agencies as the Company from time to time may designate
for such purpose, in such coin or currency of the United States of America as at
the time of payment is legal tender for the payment of public and private debts,
provided, however, that, at the option of the Company, payment of the interest
on this Security may be made only upon presentation and surrender hereof at any
such office or agency and, at the option of the Company, payment of interest may
be made by check mailed to the address of the Person entitled thereto as such
address shall appear in the Security Register. Payment of


<PAGE>


interest, if any, in respect of this Security may also be made, in the case of a
Holder of at least U.S. $1,000,000 aggregate principal amount of Securities, by
wire transfer to a U.S. Dollar account maintained by the Holder with a bank in
the United States; provided that such Holder elects payment by wire transfer by
giving written notice to the Trustee or Paying Agent to such effect designating
such account no later than 15 days immediately preceding the relevant due date
for payment (or such other date as the Trustee may accept in its discretion).

         REFERENCE IS HEREBY MADE TO THE FURTHER PROVISIONS OF THIS SECURITY SET
FORTH ON THE REVERSE HEREOF, WHICH FURTHER PROVISIONS SHALL FOR ALL PURPOSES
HAVE THE SAME EFFECT AS IF SET FORTH AT THIS PLACE.

         Unless the certificate of authentication hereon has been executed by
the Trustee referred to on the reverse hereof by manual signature, this Security
shall not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.




<PAGE>




         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

                                  MIDAMERICAN FUNDING, LLC

                                  By: /s/ Patrick J. Goodman
                                     ---------------------------
                                     Name:  Patrick J. Goodman
                                     Title:  Vice President and Treasurer

                                  Attest:

                                  By: /s/ Steven A. McArthur
                                     ---------------------------
                                     Name:  Steven A. McArthur
                                     Title:  Vice President and Secretary



<PAGE>




                     TRUSTEE'S CERTIFICATE OF AUTHENTICATION

         This is one of the Securities of the series designated herein and
referred to in the within-mentioned Indenture.

                                            THE BANK OF NEW YORK,
                                              as Trustee

                                            By: /s/ Robert A. Massimillo
                                                ------------------------------
                                                Authorized Signatory

Dated:  March 6, 2000




<PAGE>




                REVERSE OF SENIOR SECURED EXCHANGE NOTE DUE 2009

                            MIDAMERICAN FUNDING, LLC
                      6.339% Senior Secured Notes due 2009

1. General

         This Security is one of a duly authorized issue of securities of the
Company (herein called the "Securities"), issued and to be issued in one or more
series under an Indenture, dated as of March 11, 1999 (herein called the
"Original Indenture"), between the Company and The Bank of New York (as
successor to IBJ Whitehall Bank & Trust Company) as trustee (herein called the
"Trustee," which term includes any successor trustee under the Original
Indenture), as supplemented by the First Supplemental Indenture, dated as of
March 11, 1999 (together with the Original Indenture, the "Indenture") between
the Company and the Trustee, to which Indenture and all indentures supplemental
thereto reference is hereby made for a statement of the respective rights,
limitations of rights, duties and immunities thereunder of the Company, the
Trustee and the Holders of the Securities and of the terms upon which the
Securities are, and are to be, authenticated and delivered. Terms defined in the
Indenture which are not defined herein are used with the meanings assigned to
them in the Indenture. This Security is one of the series designated on the face
hereof, limited in aggregate principal amount to $175,000,000.

2. Optional Redemption

         The Securities of this series will be redeemable in whole or in part,
at the option of the Company at any time, at a Redemption Price equal to the
greater of (i) 100% of the principal amount of the Securities of this series
being redeemed or (ii) the sum of the present values of the remaining scheduled
payments of principal of and interest on the Securities of this series being
redeemed discounted to the Redemption Date on a semiannual basis (assuming a
360-day year consisting of twelve 30-day months) at a discount rate equal to the
Treasury Yield plus 15 basis points, plus, for (i) or (ii) above, whichever is
applicable, accrued interest on the Securities of this series to the Redemption
Date.

         "Treasury Yield" means, with respect to any Redemption Date, the rate
per annum equal to the semiannual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as
a percentage of its principal amount) equal to the Comparable Treasury Price for
such Redemption Date.

         "Comparable Treasury Issue" means the United States Treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining term of the Securities of this series to be redeemed that would be
utilized, at the time of selection and in accordance with customary financial
practice, in pricing new issues of corporate debt securities of comparable
maturity to the remaining term of the Securities of this series.

<PAGE>


         "Comparable Treasury Price" means, with respect to any Redemption Date,
(i) the average of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount) on the third
Business Day in New York City preceding such Redemption Date, as set forth in
the daily statistical release (or any successor release) published by the
Federal Reserve Bank of New York and designated "Composite 3:30 p.m. Quotations
for U.S. Government Securities" or (ii) if such release (or any successor
release) is not published or does not contain such prices on such Business Day,
the Reference Treasury Dealer Quotation for such Redemption Date.

         "Independent Investment Banker" means an investment banking institution
of international standing appointed by the Company.

         "Reference Treasury Dealer" means a primary U.S. Government securities
dealer in New York City appointed by the Company.

         "Reference Treasury Dealer Quotation" means, with respect to the
Reference Treasury Dealer and any Redemption Date, the average, as determined by
the Company, of the bid and asked prices for the Comparable Treasury Issue
(expressed in each case as a percentage of its principal amount and quoted in
writing to the Company by such Reference Treasury Dealer at 5:00 p.m. on the
third Business Day in New York City preceding such Redemption Date).

         Notice of  redemption  pursuant to this  paragraph 2 shall be given
as provided for in the Indenture not less than 30 days nor more than 60 days
prior to the Redemption Date.

         If fewer than all the Securities of this series are to be redeemed,
selection of Securities of this series for redemption will be made by the
Trustee in any manner the Trustee deems fair and appropriate.

         The Trustee may conclusively rely on an Officers' Certificate setting
forth the calculation of the Redemption Price, which Officers' Certificate shall
be delivered to the Trustee prior to the Redemption Date.

         Unless the Company defaults in payment of the Redemption Price, from
and after the Redemption Date, the Securities of this series or portions thereof
called for redemption will cease to bear interest, and the Holders thereof will
have no right in respect of such Securities of this series except the right to
receive the Redemption Price thereof.

         In the event of redemption of this Security in part only, the Trustee
will reduce the Principal Amount hereof by endorsement on Schedule A hereto such
that the Principal Amount shown on Schedule A after such endorsement will
reflect only the unredeemed portion hereof.

3. Defeasance

         The Indenture contains provisions for defeasance of (a) the entire
indebtedness of this Security and (b) certain restrictive covenants upon
compliance by the Company with certain conditions set forth therein.
<PAGE>

4. Defaults and Remedies

         If an Event of Default with respect to Securities of this series shall
occur and be continuing, the principal of the Securities of this series may be
declared due and payable in the manner and with the effect provided in the
Indenture. At any time after such declaration of acceleration with respect to
Securities of this series has been made, but before a judgment or decree for
payment of money has been obtained by the Trustee as provided in the Indenture,
if all Events of Default with respect to Securities of this series have been
cured or waived (other than the non-payment of principal of the Securities of
this series which has become due solely by reason of such declaration of
acceleration) then and in every such case, the Holders of a majority in
aggregate principal amount of the Outstanding securities under the Indenture
may, by written notice to the Company and to the Trustee, rescind and annul such
declaration and its consequences on behalf of all of the Holders, but no such
recision or annulment shall extend to or affect any subsequent default or impair
any right consequent thereon.

         As provided in and subject to the provisions of the Indenture, the
Holder of this Security shall not have the right to institute any proceeding,
judicial or otherwise, with respect to the Indenture, or for the appointment of
a receiver, or trustee or for any other remedy thereunder, unless (a) such
Holder shall have previously given the Trustee written notice of a continuing
Event of Default with respect to the Securities, (b) the Holders of not less
than 33% or a majority, as applicable, in principal amount of the Securities at
the time Outstanding under the Indenture shall have made written request to the
Trustee to institute proceedings in respect of such Event of Default as Trustee,
(c) such Holder shall have offered the Trustee indemnity satisfactory to the
Trustee against the costs, expenses and liabilities to be incurred in compliance
with such request, (d) the Trustee shall not have received from the Holders of a
majority in principal amount of Securities at the time Outstanding under the
Indenture a direction inconsistent with such request and (e) the Trustee for 90
days after its receipt of such notice from the Holder, request and offer of
indemnity shall have failed to institute any such proceeding. The foregoing
shall not apply to certain suits described in the Indenture, including any suit
instituted by the Holder of this Security for the enforcement of any payment of
principal hereof or any premium or interest hereon on or after the respective
due dates expressed herein.

5. Amendment and Waiver

         The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the Indenture or any supplemental
indenture or the rights and obligations of the Company and rights of the Holders
of the Securities of any series at any time by the Company and the Trustee with
the consent of the Holders of a majority in aggregate principal amount of the
Securities at the time Outstanding of each series to be affected. The Indenture
also contains provisions permitting the Holders of specified percentages in
principal amount of the Securities of each series at the time Outstanding, on
behalf of the Holders of all Securities of such series, to waive compliance by
the Company with certain provisions of the Indenture and certain past defaults
under the Indenture and their consequences. Any such consent or waiver by the
Holder of this Security shall be conclusive and binding upon such Holder and
upon all future Holders of this Security and of any Security issued upon the
registration of transfer hereof or in exchange herefor on in lieu hereof,
whether or not notation of such consent or waiver is made upon this Security.

<PAGE>

         No reference herein to the Indenture and no provision of this Security
or of the Indenture shall alter or impair the obligation of the Company, which
is absolute and unconditional, to pay the principal of (and premium, if any) and
interest, if any, on this Security at the times, place and rate, and in the coin
or currency, herein prescribed.

6. Transfer and Exchange; Denominations

         As provided in the Indenture and subject to certain limitations therein
set forth, the transfer of this Security is registrable in the Security
Register, upon surrender of this Security for registration of transfer at the
office or agency of the Company in the Borough of Manhattan, The City of New
York, (which initially shall be the corporate trust office of the Trustee), duly
endorsed by, or accompanied by a written instrument of transfer in form
satisfactory to the Company and the Security Registrar duly executed by, the
Holder hereof or his attorney duly authorized in writing, and thereupon one or
more new Securities, of authorized denominations and for the same aggregate
principal amount, shall be issued to the designated transferee or transferees.

         The Securities of this series are issuable only in registered form,
without coupons, in denominations of $1,000 and any integral multiple thereof.
As provided in the Indenture and subject to certain limitations therein set
forth, Securities of this series are exchangeable for a like aggregate principal
amount of Securities of this series and of like tenor of a different authorized
denomination as requested by the Holder surrendering the same.

         No service charge shall be made for any such registration of transfer
or exchange, but the Company may require payment of a sum sufficient to cover
any tax or other governmental charge payable in connection therewith.

7. Successor Obligors

         When a successor assumes all the obligations of its predecessor under
the Securities of this series and the Indenture in accordance with the terms of
the Indenture, the predecessor will be released from those obligations.

8. Trustee Dealings with the Company

         The Trustee under the Indenture, in its individual or any other
capacity, may become the owner or pledgee of Securities of this series and may
otherwise deal with the Company, its Subsidiaries or their respective Affiliates
as if it were not the Trustee.

9. No Recourse Against Others

         No stockholder, director, officer, employee, incorporator or Affiliate
of the Company shall have any liability for any obligation of the Company under
the Securities of this series or the Indenture or for any claim based on, in
respect of or by reason of, such obligations or their creation. Each Holder of
the Securities of this series by accepting a Security of this series waives and
releases all such liability. The waiver and release are part of the
consideration for the issuance of the Securities of this series.

<PAGE>

10. Authentication

         This Security shall not be valid until the Trustee or authenticating
agent signs the certificate of authentication on this Security.

11. CUSIP Numbers

         Pursuant to a recommendation promulgated by the Committee on Uniform
Security Identification Procedures, the Company will cause CUSIP numbers to be
printed on the Securities of this series as a convenience to the Holders of the
Securities of this series.

12. Governing Law

         This Security shall be governed by and construed in accordance with the
laws of the State of New York, without giving effect to the principles of
conflict of laws thereof.

13. Defined Terms

         All terms used in this Security which are defined in the Indenture
shall have the meanings assigned to them in the Indenture.



<PAGE>



                                   SCHEDULE A

                             SCHEDULE OF ADJUSTMENTS

Initial Principal Amount:          U.S. $175,000,000

                                                                 Notation made
                                                  Principal      on behalf of
Date              Principal       Principal       Amount         the Security
adjustment        Amount          Amount          following      Exchange
made              increase        decrease        adjustment     Agent/Registrar
----------        ----------      ---------       ----------     ---------------