Do You Need a Permit to Install or Replace an AC Unit in California?

Short answer: yes. In California, installing a new air conditioner or replacing an existing one almost always requires a permit. It surprises a lot of homeowners — and even some contractors who assume a “simple swap” is exempt — but a central AC changeout is a permitted alteration to the home's mechanical system, and the state energy code adds testing requirements on top.

Here's exactly when a permit is required, what the Title 24 energy code adds for cooling equipment, the narrow cases that don't need one, and what actually happens if an AC unit was already installed without a permit.

When You Need a Permit for an AC Unit

A mechanical permit is required for essentially any AC work that changes the equipment, including:

• Installing a new central air conditionerwhere there wasn't one before.
• Replacing an existing AC or condenser — even a like-for-like swap of the same tonnage.
• Replacing the outdoor condensing unit on its own, because it changes the refrigerant system.
• Adding or relocating a mini-split or ductless system (covered in detail in our mini-split permit guide).
• Any install that adds electrical circuits or a disconnect, which can trigger a separate electrical permit.

The reason a “simple replacement” still needs a permit is that California treats AC equipment changes as alterations regulated by both the building code and the energy code. The permit is what lets the city verify the work meets current code — not the code in force when the house was built.

Title 24 and HERS Testing: The Part People Miss

This is where AC permits differ from a lot of other home work. Under the Title 24 energy code, most central AC changeouts in California require HERS verification — independent testing by a certified rater confirming:

• Refrigerant charge is correct (the most common HERS test for AC work).
• Airflow across the coil meets the minimum.
• Duct leakage is within limits if any ductwork is altered or replaced.

You also have to meet the minimum efficiency for your climate zone (SEER2/EER2 ratings) and file the CF-1R, CF-2R, and CF-3R compliance documents. The HERS certificate is what closes out the permit — skip it and the permit stays open even if the equipment runs fine.

What Does Not Need a Permit

The exemptions are narrow. Generally, you do not need a permit for:

• Repairs to components — replacing a capacitor, contactor, fan motor, or thermostat.
• Recharging refrigerant during a service call (though chronic leaks point to a replacement that would need one).
• Cleaning, maintenance, and minor part swapsthat don't alter the system.

The rule of thumb: repairing a component is exempt; replacing the equipment is not. When in doubt, the jurisdiction's mechanical division makes the call — and the cost of asking is far lower than the cost of guessing wrong.

What Happens If You Install an AC Without a Permit

Plenty of AC units get installed without a permit every year. The consequences usually aren't immediate — which is exactly why people skip it — but they stack up:

• Stop-work orders and retroactive fees.If the city finds out, you may owe the permit fee plus penalties, and the work can be halted until it's legalized.
• Exposing the work for inspection. An inspector may require access to verify what was installed, including refrigerant charge and electrical connections.
• Voided warranties.Manufacturers can deny equipment warranty claims when the install wasn't permitted or HERS-verified.
• Insurance problems. If unpermitted equipment causes a fire or water damage, a carrier can dispute the claim.
• Home-sale disclosure. Unpermitted work has to be disclosed and frequently kills or delays escrow — see our guide on unpermitted HVAC work and home sales.
• Contractor liability. For licensed pros, repeated unpermitted work can trigger CSLB discipline. We cover the exposure in HVAC work without a permit.

How to Legalize an AC Unit Installed Without a Permit

If a unit is already in, you can usually pull a retroactive (after-the-fact) permit:

1. Apply for the mechanical permit and disclose that the work is already done.
2. Pay the permit fee, plus any investigation or penalty fee the city adds.
3. Schedule inspection and provide access so the inspector can verify the install.
4. Complete HERS testing for refrigerant charge (and duct leakage if applicable).
5. Correct anything that fails, then close out the permit.

It's cheaper and faster to permit it up front, but legalizing after the fact is almost always better than leaving an open, unpermitted install on the property.

Permit Costs and Timelines Vary by City

AC permit fees and turnaround differ significantly across California jurisdictions. Many cities issue a residential mechanical permit over the counter or online the same day; others route it through plan review. You can look up the specific requirements, fees, and timelines for your city in our permits by city directory, and see typical numbers in our Bay Area HVAC permit cost breakdown.

Frequently Asked Questions

Do you need a permit to replace an AC unit in California?

Yes. A central AC or condenser replacement requires a mechanical permit in nearly every California jurisdiction, and most changeouts also require Title 24 compliance and HERS testing.

Does replacing just the condenser need a permit?

In most cities, yes — swapping the outdoor condensing unit changes the refrigerant system and triggers HERS refrigerant-charge verification. Repairing a component like a fan motor or capacitor generally does not.

What happens if an AC was installed without a permit?

You can face retroactive fees, failed inspections, voided warranties, insurance disputes, and disclosure problems at sale. The fix is usually an after-the-fact permit plus inspection and HERS testing.

Is HERS testing required when replacing an AC?

Usually. Most central AC changeouts in California require HERS verification of refrigerant charge, and duct leakage testing if ductwork is altered. The HERS certificate is needed to close the permit.