AC Installation Cost in Round Rock, TX (2026)

Full-system replacement in Round Rock plans between $8,000 and $18,000, with the city's signature variable sitting in the attic: two-story homes with builder-grade ductwork, where the hot-upstairs problem tempts people toward oversized equipment when the honest fix is airflow design.

What moves the number

• The duct inspection. Leaky builder-grade ducts waste new-equipment gains; sealing or replacement ($1,000–$6,000) is often the highest-return line on the bid.
• Zoning. A second zone for upstairs ($1,500–$4,500 added) fixes the two-story complaint at the design level — price it as its own line so the increment is visible.
• Load calculation. Required for honest sizing; oversizing short-cycles and dehumidifies poorly in this humidity. "Same as before" is not a calculation.
• In-house crews vs. subs. Worth asking; accountability on callbacks differs, and local reviews notice.
• Permit. Round Rock requires one on replacements; skipping it is a red flag, not a savings.

Planning ranges

Round Rock / Williamson County planning bands, 2026 — not quotes. Get written, itemized scopes before deciding.

Item	Low	Typical	High
Diagnostic-confirmed repair alternative	$150	$500	$1,800
Full system, 3-ton (typical)	$8,000	$11,500	$15,000
Full system, 4–5 ton / two-story	$10,000	$13,500	$18,000
Zoning add-on	$1,500	$2,800	$4,500
Duct sealing/replacement add-on	$1,000	$2,500	$6,000

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