Quick answer

Most residential AC installations take one to three days, depending on system type, existing conditions, and permits. A like-for-like central air replacement with usable ducts is commonly finished in a single day. Adding or replacing ducts, switching to a heat pump, or setting a rooftop package unit can extend the timeline. Commercial projects and complex custom homes often require multiple days or staged work.

Typical timelines by system

• Ductless mini-split (single-zone, good access): about 4–8 hours (one day)
• Ductless multi-zone (2–5 heads): 1–3 days, depending on line lengths and access
• Central split system, replacing similar equipment with sound ducts: 6–10 hours
• Central air with new or majorly repaired ductwork: 2–5 days
• Heat pump conversion with electrical upgrades: 2–4 days
• Rooftop package unit swap (crane, curb/adapter as needed): 1 day on site plus scheduling
• Light commercial (small office/retail): 1–3 days per system; larger systems can take longer

These are working-time estimates. Permitting, inspections, equipment lead times, and utility coordination may add calendar days.

What actually happens before and during installation

1. Load calculation and design: A proper Manual J/S/D-style design (or equivalent) informs equipment size, duct sizing, and airflow. Skipping this risks comfort and efficiency issues.
2. Permit and scheduling: In California jurisdictions, permits and inspections are commonly required. Energy code compliance (Title 24) and HERS verification may be part of the process. Permit intake can range from same day to several business days, depending on the city or county.
3. Equipment logistics: Most standard equipment is available quickly; specialty capacities, low-profile air handlers, or high-efficiency heat pumps may require extra lead time.
4. Protection and removal: On install day, floors and work areas are protected, old equipment is safely removed, and refrigerant is recovered per EPA rules.
5. Set equipment: The new condenser or package unit is set on a pad or roof curb (seismic strapping is typical in California). Air handler or furnace/coil is set and leveled.
6. Lines, drains, and power: Refrigerant lines are routed and brazed with nitrogen purging, then pressure-tested and evacuated (deep vacuum) before charging. Condensate drains are pitched and trapped properly, and electrical is connected with correct wire gauge, breaker, and disconnect.
7. Ductwork and airflow: New ducts are installed or existing ducts are repaired, sealed, and balanced. Static pressure and CFM per ton are verified.
8. Controls and commissioning: Thermostat or controls are configured; refrigerant charge is verified via subcool/superheat. Commissioning checklists are completed; HERS tests (where required) are scheduled.
9. Inspection: A building inspection and any HERS verification close out the permit.

Key factors that change the timeline

• Access: Attics, crawlspaces, and tight chases slow work. Roof setups require crane coordination and sometimes curb adapters.
• Duct condition: Leaky, undersized, or damaged ducts add time to fix or replace and are often necessary to meet code and comfort goals.
• Electrical capacity: Heat pump conversions or larger systems may need a new circuit, panel upgrade, or dedicated disconnect.
• Refrigerant lines: Reusing existing lines is not always advisable; routing new line sets through finished walls takes longer.
• Condensate handling: Pumps, secondary pans, and properly trapped drains add steps—important for preventing water damage.
• Code and verification: Title 24 documentation and HERS testing can add visits or coordination days in California.
• Site conditions: Mold, asbestos, or structural issues must be addressed before the install continues.
• Weather and demand: Heat waves can extend scheduling lead times across the region.

When a one-day install is realistic

• You are replacing similar-capacity equipment in the same locations.
• Ducts are in good shape and sized correctly.
• Electrical and condensate are already compliant.
• Permit is approved and inspection is scheduled promptly.

When to expect multiple days

• New central system in a home without existing ducts.
• Heat pump conversion with panel or circuit upgrades.
• Multi-zone ductless with long or difficult line routes.
• Rooftop equipment requiring crane time, curb adapters, or roof work.
• Commercial spaces with controls integration and balancing needs.

DIY vs. licensed installation

Air conditioning work involves high-voltage electrical, pressurized refrigerants, fall hazards (attics and roofs), combustion safety (in mixed systems), and code compliance. Improper installations can create fire risks, refrigerant leaks, water damage, and structural issues. Many manufacturers limit warranties to licensed installations, and insurers or home warranties frequently require permitted work and licensed contractors for coverage. In short, DIY is risky and can cost more in the long run.

Quality checks that protect performance and health

• Correct sizing via load calculations to prevent short cycling and humidity issues.
• Verified airflow and static pressure with documented readings.
• Nitrogen purged brazing, pressure testing, and deep vacuum to avoid moisture and contamination.
• Charge verified by weight and measurements (subcool/superheat).
• Duct sealing and filtration upgrades to support clean, healthy indoor air.

Who we are

#1 AC Guys is a family-owned HVAC team in Southern California, built by a fourth generation of engineers with 80+ years of engineering experience. Our mission is simple: healthier air at home for a healthier life. Our engineers trained at manufacturer facilities for Fujitsu (Japan), Mitsubishi Elektrik (Thailand), Midea (China), Gree (China), and Hier (China). We handle both residential and commercial systems and excel at large, complex projects that demand careful design, precise installation, and thorough commissioning.

Service area

We serve Los Angeles County and nearby areas, including Orange County, Ventura County, and Western Riverside County. Common cities we reach include Los Angeles, Long Beach, Pasadena, Burbank, Glendale, Santa Monica, Torrance, West Hollywood, Beverly Hills, Anaheim, Irvine, Costa Mesa, Huntington Beach, Newport Beach, Tustin, Fullerton, Garden Grove, Ventura, Oxnard, Thousand Oaks, Simi Valley, Camarillo, Moorpark, Riverside (western), Corona, Norco, Eastvale, and Chino Hills.

FAQ: scheduling and expectations

• How early should I book? Outside peak season, one to two weeks is typical. During heat waves, plan earlier.
• Will permits slow things down? Some cities approve quickly; others take a few business days. Inspections usually occur the next business day after request.
• Can existing ducts be reused? Sometimes. If ducts are leaky or undersized, replacing them adds time but saves energy and improves comfort.
• What speeds up the job? Clear access to attics or rooftops, pre-approved permits, confirmed equipment selections, and early electrical readiness.

Bottom line

Expect a straightforward replacement to take about a day and more complex projects to take several days, plus calendar time for permits and inspections. A professional, code-compliant installation not only protects warranties and insurance coverage—it delivers the comfort, efficiency, and healthy indoor air you’re paying for.