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                                                                   EXHIBIT 10.12



[BANK OF AMERICA LOGO]

                                                          AMENDMENT TO DOCUMENTS
================================================================================
                   FIFTH AMENDMENT TO BUSINESS LOAN AGREEMENT

This FIFTH Amendment to BUSINESS LOAN AGREEMENT is entered into as of DECEMBER
31, 1999, among Bank of America, N.A ("Bank") and POWELL INDUSTRIES,
INC.("Borrower").

                                    RECITALS

A.   WHEREAS, Bank and Borrower have entered into that certain BUSINESS LOAN
     AGREEMENT dated AUGUST 21, 1997, and amended on SEPTEMBER 16, 1998,
     SEPTEMBER 26, 1998, OCTOBER 15, 1998 AND FEBRUARY 26, 1999 (collectively
     the "Agreement"); and

B.   WHEREAS, Borrower and Bank desire to amend certain terms and provisions of
     said Agreement as more specifically hereinafter set forth.

                                     AGREED

NOW, THEREFORE, in consideration of the foregoing recitals and other valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
Bank and Borrower mutually agree to amend said Agreement as follows:

     1.   In Paragraph 1.1 (Line of Credit Amount) of the Agreement, the amount
          "FIFTEEN MILLION AND NO/100 DOLLARS ($15,000,000.00) is substituted
          for the amount "Twenty Million and No/100 Dollars ($20,000,000.00)

     2.   In Paragraph 1.2 (Availability) of the Agreement, the date "FEBRUARY
          28, 2002" is substituted for the date "February 28, 2001".

     3.   In Paragraph 1.5 (Letters of Credit) Paragraph 2, the amount of
          "FIFTEEN MILLION AND NO/100 ($15,000,000.00) is substituted for Twenty
          Million and No/100 Dollars ($20,000,000.00).

          The Fee Amount for Letters of Credit issued with EXPIRATIONS GREATER
          THAN 366 days is amended to read 3/4% per annum.

     4.   In Paragraph 1.7 (Offshore Rate) the Funded Debt to EBITDA and
          Percentage Amount is amended as follows:


     FUNDED DEBT TO EBITDA                   PERCENTAGE AMOUNT
     ---------------------                   -----------------
     <1.25                                        0.75%
     >=1.25 but <1.75                             1.00%
     >=1.75                                       1.25%

     5.   In renumbered Paragraph 3.1 (a) (Unused Commitment Fee) the Unused
          Commitment Dee is amended as follows:

     FUNDED DEBT TO EBITDA                   COMMITMENT FEE
     ---------------------                   --------------
     <1.25                                        0.20%
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     >=1.25 but <1.75                        0.25%

     >=1.75                                  0.25%

6.   In renumbered Paragraph 7.3 (Tangible Net Worth) the first paragraph is
     amended to read as follows:

     7.3  Tangible Net Worth. To maintain Tangible Net worth beginning
          October 31, 1999 equal to at least Seventy Five Million and No. 100
          Dollars ($75,000,000.00) plus (i) 50% of cumulative positive net
          income after taxes for fiscal year's end after October 31, 1999, plus
          (ii) 100% of additional equity contributions.

7.   In renumbered Paragraph 7.6 (Other Debts) item (d) is amended to read as
     follows:

     Additional direct or contingent debts for business purposes which do not
     exceed a total principal amount of Five Million and No/100 ($5,000,000.00)
     outstanding at any one time and shall not rank senior in right of payment
     to Bank's debt.

8.   In renumbered Paragraph 7.17 is being amended to include (f) Management
     Change. Borrower may not make any substantial change in its present
     executive or management personnel.

This Amendment will become effective as of the date first written above,
provided that each of the following conditions precedent have been satisfied in
a manner satisfactory to Bank:

   The Bank has received from the Borrower a duly executed original of this
   Amendment, together with a duly executed Guarantor Acknowledgment and Consent
   in the form attached hereto (the "Consent").

Except as provided in this Amendment, all of the terms and provisions of the
Agreement and the documents executed in connection therewith shall remain in
full force and effect. All references in such other documents to the Agreement
shall hereafter be deemed to be references to the Agreement as amended hereby.

THIS WRITTEN AMENDMENT AND THE DOCUMENTS EXECUTED IN CONNECTION HEREWITH
REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED
BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE
PARTIES.

IN WITNESS WHEREOF, this Amendment has been executed by the parties hereto as
of the date first written above.

BANK OF AMERICA, N.A.

By:
   --------------------------
(Bank Officer Name, Title)



POWELL INDUSTRIES, INC.

By: /s/ J.F. AHART
   --------------------------
J.F. Ahart, Vice President