Document:

<PAGE>

                                                                    EXHIBIT 10.1

                                 THIRD AMENDMENT

         THIRD AMENDMENT (this "Amendment"), dated as of December 31, 2001, to
the Credit Agreement, dated as of May 22, 2001 (as further amended, supplemented
or modified from time to time, the "Credit Agreement"), among Integrated
Electrical Services, Inc., a Delaware corporation (the "Borrower"), certain
financial institutions which are or may become parties thereto (the "Banks"),
Credit Lyonnais and The Bank of Nova Scotia, as syndications agents, Toronto
Dominion (Texas), Inc., as documentation agent, and JPMorgan Chase Bank, as
administrative agent (in such capacity, the "Administrative Agent").

                                   WITNESSETH:
                                   -----------

         WHEREAS, pursuant to the Credit Agreement, the Banks have agreed to
make, and have made, certain loans and other extensions of credit to the
Borrower;

         WHEREAS, the Borrower has requested that the Administrative Agent and
the Banks amend a certain provision of the Credit Agreement; and

         WHEREAS, the Administrative Agent and the Banks are willing to agree to
the requested amendment on the terms and conditions contained herein;

         NOW, THEREFORE, the parties hereto hereby agree as follows:

         I. Defined Terms. Terms defined in the Credit Agreement and used herein
shall have the meanings given to them in the Credit Agreement, as amended
hereby.

         II. Amendments to the Credit Agreement.

         1. The definition of "Applicable Margin" set forth in Section 1.1 of
the Credit Agreement is hereby amended to read in its entirety as follows:

                  "Applicable Margin" means, with respect to interest rates and
         letter of credit fees and as of any date of its determination, an
         amount equal to the percentage amount set forth in the table below
         opposite the applicable ratio of (a) the consolidated Total Debt of the
         Borrower as of the end of the fiscal quarter then most recently ended
         to (b) the consolidated EBITDA of the Borrower for the four fiscal
         quarters then most recently ended:

<PAGE>

<Table>
<Caption>
                              Applicable Margin
                              LIBOR Tranches and        Applicable Margin
 Total Debt to EBITDA        Letter of Credit Fee       Prime Rate Tranche
 --------------------        --------------------       ------------------
<S>                          <C>                        <C>
        <1.50                       1.75%                     0.25%
        -

   >1.50 but <2.00                  2.00%                     0.50%
             -

   >2.00 but <2.50                  2.25%                     0.75%
             -

   >2.50 but <3.00                  2.50%                     1.00%
             -

   >3.00 but <3.50                  2.75%                     1.25%
             -

   >3.50 but <4.00                  3.00%                     1.50%
             -

   >4.00 but <4.50                  3.25%                     1.75%
             -

        >4.50                       3.50%                     2.00%

</Table>

         The foregoing ratio and resulting Applicable Margin shall be based upon
         Schedule C of the most recent Compliance Certificate delivered to the
         Administrative Agent pursuant to Section 5.2(a) or Section 5.2(b).

         Any adjustments to the Applicable Margin shall become effective on the
         45th day following the last day of each fiscal quarter or on the 90th
         day following the last day of each fiscal year as applicable; provided,
         however, that if any such Compliance Certificate is not delivered when
         required hereunder, the Applicable Margin shall be deemed to be the
         maximum percentage amount in each table from such 45th or 90th day
         until such Compliance Certificate is received by the Administrative
         Agent.

         Upon any change in the Applicable Margin, the Administrative Agent
         shall promptly notify the Borrower and the Banks of the new Applicable
         Margin.

         2. Section 5.5(b)(ii) of the Credit Agreement (Maximum Total Debt to
EBITDA Ratio) is hereby amended to read in its entirety as follows:

                  (ii) Maximum Total Debt to EBITDA Ratio. As of the last day of
         each fiscal quarter of the Borrower, the Borrower shall not permit the
         ratio of (a) the consolidated Total Debt of the Borrower as of end of
         such fiscal quarter minus, so long as there are no outstanding
         Revolving Loans as of such date, cash on the consolidated balance sheet
         of the Borrower as of such date to (b) the consolidated EBITDA of the
         Borrower for the preceding four fiscal quarters then ended, to be
         greater than the applicable ratios set forth below as of the dates
         indicated:

<Table>
<Caption>
                  Fiscal Quarter Ending                       Ratio
                  ---------------------                       -----
<S>                                                           <C>
                  December 31, 2001                           3.50 to 1.00
                  March 31, 2002                              4.25 to 1.00
                  June 30, 2002                               4.75 to 1.00
                  September 30, 2002                          4.25 to 1.00
                  December 31, 2002                           4.00 to 1.00
                  March 31, 2003                              3.75 to 1.00
                  June 30, 2003                               3.50 to 1.00
                  September 30, 2003 and each
                    fiscal quarter thereafter                 3.25 to 1.00
</Table>

<PAGE>

         3. Section 5.5(c) of the Credit Agreement (Minimum Interest Coverage
Ratio) is hereby amended to read in its entirety as follows

                  (c) Minimum Interest Coverage Ratio. As of the last day of
         each fiscal quarter, the Borrower shall not permit the ratio of (i) the
         consolidated EBIT of the Borrower for the preceding four fiscal
         quarters then ended to (ii) the consolidated Interest Expense of the
         Borrower (to the extent paid in cash) for the preceding four fiscal
         quarters then ended minus any income of the Borrower or any of its
         consolidated Subsidiaries during such period which is attributable to
         any Interest Hedge Agreement plus any expenses of the Borrower or any
         of its consolidated Subsidiaries during such period which is
         attributable to any Interest Hedge Agreement, to be less than the
         applicable ratios set forth below as of the dates indicated:

<Table>
<Caption>
                  Fiscal Quarter Ending                       Ratio
                  ---------------------                       -----
<S>                                                           <C>
                  December 31, 2001                           2.25 to 1.00
                  March 31, 2002                              1.75 to 1.00
                  June 30, 2002                               1.50 to 1.00
                  September 30, 2002                          1.75 to 1.00
                  December 31, 2002                           2.00 to 1.00
                  March 31, 2003                              2.25 to 1.00
                    fiscal quarter thereafter                 2.50 to 1.00
</Table>

         Compliance with this paragraph (c) shall be determined in the
         applicable Compliance Certificate based upon the adjusted financial
         reports contained in Schedule A of such Compliance Certificate.

         III. Conditions to Effectiveness. This Amendment shall become effective
on the date on which this Amendment shall have been executed by the Borrower,
the Administrative Agent and the Majority Banks and the Borrower shall have paid
to the Administrative Agent, for disbursement to each Bank which joins in the
execution of this Amendment, a fee in an amount equal to 0.20% of the Commitment
of each such Bank.

         IV.  General.

         1. Representations and Warranties. The Borrower represents and warrants
that the representations and warranties made by the Borrower in the Credit
Documents are true and correct in all material respects on and as of the date
hereof, after giving effect to the effectiveness of this Amendment, as if made
on and as of the date hereof, and no Default or Event of Default has occurred
and is continuing.

<PAGE>

         2. Payment of Expenses. The Borrower agrees to pay or reimburse the
Administrative Agent for all of its out-of-pocket costs and reasonable expenses
incurred in connection with this Amendment, any other documents prepared in
connection herewith and the transactions contemplated hereby, including, without
limitation, the reasonable fees and disbursements of counsel to the
Administrative Agent.

         3. No Other Amendments. This Amendment shall not be construed as a
waiver or consent to any further or future action on the part of the Borrower
that would require a waiver or consent of the Administrative Agent and/or the
Banks. Except as expressly amended hereby, the provisions of the Credit
Agreement are and shall remain in full force and effect.

         4. Governing Law; Counterparts.

         (a) This Amendment and the rights and obligations of the parties hereto
shall be governed by, and construed and interpreted in accordance with, the laws
of the State of New York.

         (b) This Amendment may be executed by one or more of the parties to
this Amendment on any number of separate counterparts, and all of said
counterparts taken together shall be deemed to constitute one and the same
instrument. This Amendment may be delivered by facsimile transmission of the
relevant signature pages hereof.

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their respective proper and duly authorized
officers as of the day and year first above written.

                                       INTEGRATED ELECTRICAL SERVICES, INC.

                                       By:
                                          --------------------------------------
                                       Name:
                                            ------------------------------------
                                       Title
                                            ------------------------------------

<PAGE>

                                       JPMORGAN CHASE BANK,
                                       as Administrative Agent and as a Bank

                                       By:
                                          --------------------------------------
                                       Name:
                                            ------------------------------------
                                       Title
                                            ------------------------------------

<PAGE>

                                        CREDIT LYONNAIS, NEW YORK BRANCH,
                                        as Syndication Agent and as a Bank

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        THE BANK OF NOVA SCOTIA,
                                        as Syndication Agent and as a Bank

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        TORONTO DOMINION (TEXAS), INC.,
                                        as Documentation Agent and as a Bank

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        BANK OF SCOTLAND

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        FIRST BANK & TRUST

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        FIRSTAR BANK, N.A.

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        RZB FINANCE LLC

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

                                        SOUTHWEST BANK OF TEXAS, N.A.

                                        By:
                                           -------------------------------------
                                        Name:
                                             -----------------------------------
                                        Title
                                             -----------------------------------

<PAGE>

         The undersigned hereby join in this Amendment to evidence their consent
to execution by Borrower of this Amendment, to confirm that each Credit Document
now or previously executed by the undersigned applies and shall continue to
apply to the Credit Agreement, as amended hereby, and to acknowledge that
without such consent and confirmation, the Banks would not execute this
Amendment.

                                   1ST GROUP TELECOMMUNICATIONS, INC.
                                   ACE ELECTRIC, INC.
                                   ALADDIN WARD ELECTRIC & AIR, INC.
                                   AMBER ELECTRIC, INC.
                                   ANDERSON & WOOD CONSTRUCTION CO., INC.
                                   ARC ELECTRIC, INCORPORATED
                                   BACHOFNER ELECTRIC, INC.
                                   BEAR ACQUISITION CORPORATION
                                   BRINK ELECTRIC CONSTRUCTION CO.
                                   BRITT RICE ELECTRIC, INC.
                                   BRITT RICE MANAGEMENT LLC
                                   BRYANT ELECTRIC COMPANY, INC.
                                   BW CONSOLIDATED, INC.
                                   BW/BEC, INC.
                                   CANOVA ELECTRICAL CONTRACTING, INC.
                                   CARROLL MANAGEMENT LLC
                                   CARROLL SYSTEMS, INC.
                                   CHARLES P. BAGBY COMPANY, INC.
                                   COLLIER ELECTRIC COMPANY, INC.
                                   COMMERCIAL ELECTRICAL CONTRACTORS, INC.
                                   CROSS STATE ELECTRIC, INC.
                                   CYPRESS ELECTRICAL CONTRACTORS, INC.
                                   DANIEL ELECTRICAL CONTRACTORS, INC.
                                   DANIEL ELECTRICAL OF TREASURE COAST INC.
                                   DANIEL INTEGRATED TECHNOLOGIES, INC.
                                   DAVIS ELECTRICAL CONSTRUCTORS, INC.
                                   DELCO ELECTRIC, INC.
                                   ELECTRO-TECH, INC.
                                   EMC ACQUISITION CORPORATION
                                   ERNEST P. BREAUX ELECTRICAL, INC.
                                   FEDERAL COMMUNICATIONS GROUP, INC.
                                   FLORIDA INDUSTRIAL ELECTRIC, INC.
                                   GENERAL PARTNER, INC.
                                   GOSS ELECTRIC COMPANY, INC.
                                   H.R. ALLEN, INC.
                                   HATFIELD REYNOLDS ELECTRIC COMPANY

<PAGE>

                                   HOLLAND ELECTRICAL SYSTEMS, INC.
                                   HOUSTON-STAFFORD ELECTRIC, INC.
                                   HOUSTON-STAFFORD MANAGEMENT LLC
                                   HOWARD BROTHERS ELECTRIC CO., INC.
                                   I.C.G. ELECTRIC, INC.
                                   IES COMMUNICATIONS, INC.
                                   IES CONTRACTORS MANAGEMENT LLC
                                   IES ELECTRICAL GROUP, INC.
                                   IES PROPERTIES MANAGEMENT, INC.
                                   IES PROPERTIES, INC.
                                   IES RESIDENTIAL GROUP, INC.
                                   IES SPECIALTY LIGHTING, INC.
                                   IES VENTURES INC.
                                   INNOVATIVE ELECTRIC COMPANY, INC.
                                   INTEGRATED ELECTRICAL FINANCE, INC.
                                   INTELLIGENT BUILDING SOLUTIONS, INC.
                                   J.W. GRAY ELECTRIC CO., INC.
                                   J.W. GRAY MANAGEMENT LLC
                                   KAYTON ELECTRIC, INC.
                                   KEY ELECTRICAL SUPPLY, INC.
                                   LINEMEN, INC.
                                   MARK HENDERSON, INCORPORATED
                                   MENNINGA ELECTRIC, INC.
                                   MIDLANDS ELECTRICAL CONTRACTORS, INC.
                                   MID-STATES ELECTRIC COMPANY, INC.
                                   MILLS ELECTRICAL CONTRACTORS, INC.
                                   MILLS MANAGEMENT LLC
                                   MITCHELL ELECTRIC COMPANY, INC.
                                   M-S SYSTEMS, INC.
                                   MURRAY ELECTRICAL CONTRACTORS, INC.
                                   MUTH ELECTRIC, INC.
                                   NEAL ELECTRIC MANAGEMENT LLC
                                   NEW TECHNOLOGY ELECTRICAL CONTRACTORS, INC.
                                   NEWCOMB ELECTRIC COMPANY, INC.
                                   PAN AMERICAN ELECTRIC COMPANY, INC.
                                   PAN AMERICAN ELECTRIC, INC.
                                   PAULIN ELECTRIC COMPANY, INC.
                                   POLLOCK ELECTRIC INC.
                                   PRIMENET, INC.
                                   PRIMO ELECTRIC COMPANY
                                   PUTZEL ELECTRICAL CONTRACTORS, INC.
                                   RAINES ELECTRIC CO., INC.
                                   RAINES MANAGEMENT LLC
                                   RKT ELECTRIC, INC.

<PAGE>

                                   ROCKWELL ELECTRIC, INC.
                                   RODGERS ELECTRIC COMPANY, INC.
                                   RON'S ELECTRIC, INC.
                                   SPECTROL, INC.
                                   SPOOR ELECTRIC, INC.
                                   SUMMIT ELECTRIC OF TEXAS, INC.
                                   T&H ELECTRICAL CORPORATION
                                   TECH ELECTRIC CO., INC.
                                   TESLA POWER G.P., INC.
                                   THOMAS POPP & COMPANY
                                   VALENTINE ELECTRICAL, INC.
                                   WOLFE ELECTRIC CO., INC.
                                   WRIGHT ELECTRICAL CONTRACTING, INC.

                                   By:
                                      ------------------------------------------
                                      William Reynolds, Chief Financial Officer

                                   BRITT RICE HOLDINGS LLC
                                   BW/BEC, L.L.C.
                                   CARROLL HOLDINGS LLC
                                   DKD ELECTRIC COMPANY, INC.
                                   HOUSTON-STAFFORD HOLDINGS LLC
                                   ICS HOLDINGS LLC
                                   IES CONTRACTORS HOLDINGS LLC
                                   IES HOLDINGS LLC
                                   J.W. GRAY HOLDINGS LLC
                                   MILLS ELECTRICAL HOLDINGS LLC
                                   NBH HOLDING CO., INC.
                                   POLLOCK SUMMIT HOLDINGS INC.
                                   RAINES HOLDINGS LLC
                                   TESLA POWER (NEVADA), INC.

                                   By:
                                      ------------------------------------------
                                      Adrianne M. Horne, President

<PAGE>

                                   IES PROPERTIES HOLDINGS, INC.

                                   By:
                                      ------------------------------------------
                                      Victoria Garrett, President

                                   B. RICE ELECTRIC LP
                                   BEXAR ELECTRIC COMPANY, LTD.
                                   CARROLL SYSTEMS LP
                                   HAYMAKER ELECTRIC, LTD.
                                   HOUSTON-STAFFORD ELECTRICAL CONTRACTORS LP
                                   ICS INTEGRATED COMMUNICATION SERVICES LP
                                   IES CONTRACTORS LP
                                   IES MANAGEMENT LP
                                   IES PROPERTIES LP
                                   J.W. GRAY ELECTRICAL CONTRACTORS LP
                                   MILLS ELECTRIC LP
                                   NEAL ELECTRIC LP
                                   POLLOCK SUMMIT ELECTRIC LP
                                   POLLOCK SUMMIT ELECTRIC LP
                                   RAINES ELECTRIC LP
                                   TESLA POWER AND AUTOMATION, L.P.
                                   TESLA POWER PROPERTIES, L.P.

                                   By: ITS GENERAL PARTNER

                                       By:
                                          --------------------------------------
                                             William Reynolds,
                                             Chief Financial Officer<PAGE>
                                                                   EXHIBIT 4.2

                          AMENDMENT NO. 1 TO INDENTURE

                  THIS AMENDMENT No. 1, dated as of October 1, 2001 (the
"Amendment") is made to amend the Indenture, dated as of February 9, 2001 (as
amended, supplemented or otherwise modified from time to time, the "Indenture"),
between BRL Universal Compression Funding I, L.P. (the "Issuer") and Wells Fargo
Bank Minnesota, National Association, as indenture trustee (the "Indenture
Trustee").

                              W I T N E S S E T H:

                  WHEREAS, the parties hereto have previously entered into the
Indenture which requires the Issuer to enter into and maintain one or more
interest rate hedge agreements;

                  WHEREAS, Issuer has prepaid $38,800,000 of its Series 2001-1
Notes;

                  WHEREAS, the parties hereto wish to amend the Indenture to
provide that the Issuer will not be required to reduce the notional amount of
such interest rate hedge agreements in connection with such prepayment;

                  NOW THEREFORE, in consideration of the premises and mutual
covenants herein contained, the parties hereto agree as follows:

         Section 1. Defined Terms. Capitalized terms used in this Amendment and
not otherwise defined herein shall have the meanings assigned to such terms in
the Indenture.

         Section 2. Amendments to the Indenture. Effective on October 23, 2001,
following the execution and delivery of this Amendment, Section 630(a) of the
Indenture will be deleted in its entirety and replaced with the following:

" (a) The Issuer will enter into and maintain (or will cause to be entered into
and maintained) one or more Interest Rate Swap Agreements with one or more
Eligible Interest Rate Swap Counterparties having an aggregate notional balance:
(x) not less than 90% of the sum of the then unpaid principal balance of the
Notes of all Series then Outstanding and all outstanding Capital and (y) not
more than 100% of the Asset Base. The duration of the Interest Rate Swap
Agreements will be consistent with the Termination Dates of the Lease Pools. All
of the foregoing requirements shall be collectively referred to as the "Hedging
Requirement". "

         Section 3. Representations and Warranties. (a) Each of the parties
hereto hereby confirms that each of the representations and warranties set forth
in the Indenture made by such party are true and correct as of the date first
written above with the same effect as though each had been made by such party as
of such date, except to the extent that any of such representations and
warranties expressly relate to earlier dates.

                  (b) The Issuer hereby confirms that each of the conditions
precedent to the amendment to the Indenture have been, or contemporaneously with
the execution of this Amendment will be satisfied.

<PAGE>
         Section 4. Effectiveness of Amendment.

                  (a) This Amendment shall be binding upon and inure to the
benefit of the parties hereto and their respective successors and assigns.

                  (b) On and after the execution and delivery hereof, (i) this
Amendment shall become a part of the Indenture and (ii) each reference in the
Indenture to "this Indenture", or "hereof", "hereunder" or words of like import,
and each reference in any other document to the Indenture shall mean and be a
reference to such Indenture, as amended or modified hereby.

                  (c) Except as expressly amended or modified hereby, the
Indenture shall remain in full force and effect and is hereby ratified and
confirmed by the parties hereto.

         Section 5. Execution in Counterparts, Effectiveness. This Amendment may
be executed by the parties hereto in separate counterparts, each of which shall
be deemed to be an original and all of which shall constitute together but one
and the same agreement.

         Section 6. Governing Law. THIS AMENDMENT SHALL BE CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REFERENCE TO NEW
YORK'S CONFLICTS OF LAW PRINCIPLES, AND THE OBLIGATIONS, RIGHTS AND REMEDIES OF
THE PARTIES HEREUNDER SHALL BE DETERMINED IN ACCORDANCE WITH THE LAWS OF THE
STATE OF NEW YORK.

                            [Signature pages follow.]

                                       2
<PAGE>

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

                                     BRL UNIVERSAL COMPRESSION FUNDING I, L.P.

                                     By: BRL UNIVERSAL COMPRESSION
                                         MANAGEMENT, INC., its general manager

                                     By:/s/ Gregory C. Greene
                                        ----------------------------------------
                                     Name:  Gregory C. Greene
                                     Title: President

                                     WELLS FARGO BANK MINNESOTA,
                                     NATIONAL ASSOCIATION, not in its individual
                                     capacity but solely as indenture trustee

                                     By:/s/ Edna Barber
                                        ----------------------------------------
                                     Name: Edna Barber
                                          --------------------------------------
                                     Title: Assistant Vice President
                                           -------------------------------------

                                                    AMENDMENT NO. 1 TO INDENTURE
<PAGE>

The amendment no. 1 to the Indenture is hereby approved.

                                     FIRST UNION NATIONAL BANK

                                     By:/s/ Jane W. Workman
                                        ----------------------------------------
                                     Name: Jane W. Workman
                                          --------------------------------------
                                     Title: Senior Vice President
                                           -------------------------------------

                                     VARIABLE FUNDING CAPITAL CORPORATION

                                     By:   First Union Securities, Inc.,
                                           its attorney-in-fact

                                     By:/s/ Frank E. Weise VP
                                        ----------------------------------------
                                     Name: Frank E. Weiss
                                          --------------------------------------
                                     Title: Vice President
                                           -------------------------------------

                                                    AMENDMENT NO. 1 TO INDENTURE

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