EXHIBIT 24

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, Tana L. Pool and Joshua E.
Spooner, 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 fact's 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 13th day of September, 2007.

                                           /s/ David R. Helwig