POWER OF ATTORNEY LETTER

LIMITED POWER OF ATTORNEY
FOR SECTION 16 REPORTING OBLIGATIONS

Know all by these presents, that the undersigned hereby constitutes
and appoints each of Vincent A. Mercaldi, James H. Haddox and Tana L. Pool,
signing singly, the undersigned's true and lawful attorney in fact to:

(1) execute for and on behalf of the undersigned, in the
undersigned's capacity as a director and/or officer of Quanta Services, Inc.
(the Company), Forms 3, 4, and 5 in accordance with Section 16(a) of the
Securities Exchange Act of 1934, as amended, and the rules thereunder;

(2) do and perform any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete and execute any
such Form 3, 4, or 5, complete and execute any amendment or amendments
thereto, and timely file such form with the United States Securities and
Exchange Commission and any stock exchange or similar authority; and

(3) take any other action of any type whatsoever in
connection with the foregoing which, in the opinion of such attorney in
fact, may be of benefit to, in the best interest of, or legally required by,
the undersigned, it being understood that the documents executed by such
attorney in fact on behalf of the undersigned pursuant to this Limited Power
of Attorney shall be in such form and shall contain such terms and conditions
as such attorney in fact may approve in such attorney in facts discretion.

The undersigned hereby grants to each such attorney in fact full
power and authority to do and perform any and every act and thing whatsoever
requisite, necessary, or proper to be done in the exercise of any of the
rights and powers herein granted, as fully to all intents and purposes as the
undersigned might or could do if personally present, with full power of
substitution or revocation, hereby ratifying and confirming all that such
attorney in fact, or such attorney in fact's substitute or substitutes, shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that the
foregoing attorneys in fact, in serving in such capacity at the request of
the undersigned, are not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934, as amended.

This Limited Power of Attorney shall remain in full force and
effect until the undersigned is no longer required to file Forms 3, 4, and 5
with respect to the undersigned's holdings of and transactions in securities
issued by the Company, unless earlier revoked by the undersigned in a signed
writing delivered to the foregoing attorneys in fact. The undersigned
acknowledges that the execution of this Limited Power of Attorney shall
automatically revoke all earlier power(s) of attorney executed by the
undersigned in the undersigned's capacity as a director and/or officer of
the Company and in connection with the undersigned's obligations under
Section 16 of the Securities Exchange Act of 1934, as amended.

IN WITNESS WHEREOF, the undersigned has caused this Limited
Power of Attorney to be executed as of this 17th day of August, 2006.

s/ Gary A. Tucci