HVAC permits in LA: AC replacement, heat pumps, and what duct upgrades actually trigger

HVAC permits in LA are common but quietly complicated. Replacing a 20-year-old AC unit looks like a simple swap until you hit Title 24 energy compliance rules. Adding a heat pump for the first time involves rebate paperwork, ductwork verification, and an HERS rater inspection on top of the LADBS permit. Knowing what triggers what saves money and avoids the "your permit can't issue until you upgrade your ducts" surprise.

When you need an HVAC permit

LADBS requires a mechanical permit for any of the following:

• Replacing an existing AC unit, furnace, or heat pump
• Installing a new HVAC system in a home or addition that didn't have one
• Adding zones or new thermostats that change system control
• Installing or replacing ductwork
• Adding ventilation systems (whole-house fans, ERVs / HRVs)
• Installing mini-split (ductless) systems
• Adding gas furnaces, water heaters, or fireplaces with combustion air requirements

You don't need a permit for:

• Replacing thermostats with the same wiring
• Cleaning ducts
• Replacing filters (obviously)
• Adding a window AC unit (plug-in only, no installation)
• Replacing a damaged duct register

Most HVAC permits issue same-day or next-day through PermitLA for licensed contractors.

The Title 24 catch on AC replacement

Here's where many homeowners get surprised. Replacing a 1990s-era central AC with a new one isn't quite "like-for-like" anymore.

Title 24 is California's energy code. It applies to HVAC replacements, not just new construction. When you replace a 10+ year old AC with a new one, the new system has to meet current Title 24 efficiency standards. That includes:

Duct sealing. The existing ductwork has to be tested for leakage. Leakage above the threshold (typically 6% of supply CFM for replacement installations) means you have to seal the ducts. Cost: $500-1,500.

Refrigerant changeout. California phased out R-22 refrigerant. New systems use R-410A or newer R-454B. The old refrigerant in your existing system gets reclaimed; new system gets the new stuff. Bundled into the installer's pricing typically.

HERS verification (sometimes). If the system is over a certain capacity (typically 3 tons or more), an independent HERS rater has to verify the install meets standards. Cost: $300-500 for the HERS inspection. Adds 1-2 weeks to project timing.

Sealed combustion air for furnaces. Old gas furnaces draw combustion air from the room they're in. New ones need sealed combustion air from outside. If your existing furnace is in a closet without outside venting, the new install may require adding a vent.

Most reputable HVAC installers know about these requirements and quote accordingly. Some less-reputable ones quote a low number and pass the cost to you mid-install. Always verify the quote includes Title 24 compliance work.

Heat pump conversions: the next-generation install

California has been pushing heat pumps hard. Many incentive programs ($1,500-$8,000 rebates depending on income tier, utility, and equipment) make heat pumps cost-competitive with gas furnaces + AC.

Heat pump install is different from AC-only replacement in a few ways:

Electrical capacity. Heat pumps use more electricity than AC-only because they also provide heating. Your electrical panel may need an upgrade to accommodate the new load. (See our electrical permit guide for the panel-upgrade math.)

Ductwork compatibility. Heat pumps often need higher airflow than older gas furnaces. Old ductwork may be undersized for a heat pump. Verification is part of the install process.

Refrigerant lines. If converting from a gas furnace + AC to a heat pump, the existing AC's refrigerant lines may not be appropriate for the new system. Often replaced as part of install.

Rebate paperwork. SoCal Edison + LADWP both offer heat pump rebates. Application happens before or during install (varies by program). Documentation matters.

Total cost for a typical residential heat pump conversion: $12K-25K all-in including any panel upgrade and ductwork. After rebates: $7K-18K net cost.

Mini-splits: the ADU-friendly path

Many LA ADUs use ductless mini-split systems instead of central air. Advantages:

• No ductwork required (just a refrigerant line + condensate drain)
• High efficiency
• Independent zone control
• Quiet operation
• Compact outdoor units
• Permit and inspection less complex than central systems

Cost for a typical 12K-18K BTU mini-split serving a 500-800 sqft ADU: $4,000-7,500 installed.

The catch: Title 24 still applies. Mini-splits get inspected for proper line insulation, condensate routing, and electrical disconnects.

Common mistakes

Skipping permits on AC replacements. Some HVAC contractors offer "no permit" pricing as a cost-savings. Beyond the legal exposure (technically illegal), the issues:

• Future sale: home inspector flags missing permits
• Insurance: claims may be denied
• Re-permitting: when you eventually try to sell or refinance, getting the work permitted retroactively often requires partial demolition

Picking the cheapest installer. HVAC has a wide range of installer quality. Cheap installs often skip ductwork sealing, undersize refrigerant lines, or miss the Title 24 compliance items. Pay the premium for a CSLB C-20 licensed contractor with good reviews.

Forgetting to check duct condition before AC replacement. If your existing ducts are torn, undersized, or leaking, the new AC won't perform well. Inspecting (and ideally sealing/repairing) before install is way easier than after.

Confusing heat pump types. "Heat pump" can mean air-source heat pump (most common), mini-split heat pump (ductless), heat-pump water heater (different appliance, also rebate-eligible), or geothermal heat pump (rare). Make sure your installer specs the right type.

Not coordinating with solar. If you're planning solar, install AFTER the new HVAC. Solar sizing depends on electrical load. Adding HVAC after solar may exceed the system's capacity. Sequencing matters.

DIY vs. licensed contractor

HVAC is one of the strongest "hire it out" categories.

• Refrigerant handling requires EPA Section 608 certification. You legally cannot install or service refrigerant-containing equipment without it.
• Electrical work for HVAC (240V circuits, dedicated breakers) needs a C-10 electrician or a C-20 HVAC contractor doing the work under their license.
• Gas work (for furnaces) needs C-36 or C-20.
• Duct fabrication requires sheet-metal skills + tools most homeowners don't have.

DIY-friendly HVAC tasks: replacing filters, cleaning condenser coils, checking duct registers for blockage. That's about it.

What to do next

For AC replacement: get 3 quotes from CSLB C-20 licensed HVAC contractors. Confirm each quote includes Title 24 compliance work (duct sealing, refrigerant changeout), not extra line items added later.

For heat pump conversion: check rebate eligibility BEFORE selecting equipment. Some rebates require pre-approval. SoCal Edison, LADWP, and the federal Inflation Reduction Act (IRA) all have heat pump incentives.

For ADU planning: budget HVAC into your initial cost estimate. Mini-split for ADU is typically $5-7K; central with new ducts can be $10-15K for a small ADU.

Sources

• LADBS Mechanical Permits: ladbs.org/services/online-services/online-permitting
• California Title 24 Energy Code (Building Energy Efficiency Standards)
• California Air Resources Board (CARB) HVAC refrigerant rules
• CSLB contractor lookup: cslb.ca.gov

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Planning HVAC as part of an ADU project? Run your address, we'll flag whether your existing panel can handle a heat pump conversion in addition to ADU loads.