The short answer
Replacing a central AC, furnace or heat pump inside Austin city limits requires a mechanical permit from the City. For a straight swap of existing equipment, it's typically filed as a residential mechanical "change out" permit. Surrounding cities like Round Rock, Cedar Park and Georgetown have their own permitting rules.
Who pulls it
Your HVAC contractor does. Texas requires AC work to be performed under a licensed air conditioning contractor, and the City's permit request asks for the master license holder responsible for the job. If a contractor asks you to pull the permit yourself as a homeowner, or suggests skipping it, treat that as a red flag.
Inspection and timing
After the install, a City inspector checks the work. According to the City's permit request form, a permit expires if no inspection has been scheduled within 180 days, so make sure your contractor actually closes it out.
Why it matters to you
Permitted work is inspected work. It also protects you later: Austin Energy's AC and heat pump rebates require City permits and a post-install inspection, and an open or missing permit can come up when you sell the house.
- Required for Austin Energy rebate eligibility
- Gives you an independent check on the install
- Avoids questions at resale
Sources: City of Austin mechanical permit request · Austin Energy AC rebate requirements