Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
Most HVAC work in San Carlos requires a permit under California Title 24 and local building code. Replacement-only on existing systems may qualify for streamlined over-the-counter processing, but new installations, ductwork changes, or refrigerant handling almost always need a permit and Title 24 energy compliance certification.
San Carlos Building Department enforces California Title 24 energy standards more strictly than many Bay Area neighbors because the city sits in Climate Zones 3B-3C (coastal) with marine-layer cooling dominance — meaning HVAC sizing and duct sealing rules are tighter here than in, say, inland Palo Alto or Morgan Hill. Unlike some Peninsula cities that allow owner-builder HVAC if you pull an electrical permit separately, San Carlos explicitly requires a licensed C-20 (HVAC) contractor on most projects (though owner-builder is allowed under California B&P Code § 7044 if you hold a C-20 or hire one as the responsible managing employee). The city uses an online permit portal and generally processes HVAC permits in 3-5 business days for straightforward replacements, but new construction or major system redesigns trigger plan review by the city's energy consultant, adding 2-3 weeks. Plan review costs $250–$400 additional, on top of base permit fees of $150–$450 depending on system tonnage and scope.

What happens if you skip the permit (and you needed one)

San Carlos HVAC permits — the key details

California Title 24 (Energy Commission Standards) is the spine of HVAC permitting in San Carlos and the entire state. Any new HVAC installation, replacement of the main system (not just a component), or ductwork modification requires a California-compliant Energy Commission Certificate of Compliance (CC) signed by a licensed HVAC contractor or energy consultant. San Carlos Building Department will not issue a permit without this CC attached. The CC must document refrigerant charge, duct leakage testing (if ducts are modified or new), thermostat type, and equipment efficiency (SEER2 for cooling, AFUE for heating). For coastal San Carlos (Zones 3B-3C), the minimum SEER2 requirement is typically 16 for air conditioning and 8 HSPF2 for heat pumps as of 2024; check the current year's Title 24 standards at energy.ca.gov. The city's plan reviewer will cross-check the CC against local amendments — San Carlos has adopted the 2022 California Building Code, which includes Title 24-2022. Most homeowners don't realize Title 24 certification is separate from the permit itself; you must hire a licensed contractor or energy consultant to generate the CC before filing.

Owner-builder HVAC work is possible under California B&P Code § 7044, but with a critical catch: you must personally hold a current C-20 (HVAC) license OR employ a C-20 license holder as your responsible managing employee (RME). Most homeowners do not hold a C-20; if you attempt an HVAC project yourself without that license, you are technically violating state law, not just local code. San Carlos Building Department does not grant exemptions for owner-builder HVAC on residential properties — the rule is statewide. However, you may hire a licensed C-20 contractor to handle the refrigerant (evacuation, recovery, charge) and ductwork sealing, while managing the overall project. The permit application (available on the city's online portal) asks for contractor license numbers; provide the C-20 license or the form will be rejected. If you are a licensed C-20 and pull the permit yourself, you are the license holder of record and liable for Title 24 compliance.

Streamlined vs. full-plan-review permits: San Carlos distinguishes between straightforward equipment replacements (same capacity, same location, existing ducts reused) and complex projects. A like-for-like replacement — removing a 3-ton split-system AC and installing a new 3-ton unit in the same location — typically gets over-the-counter approval in 1-2 days if the CC is complete and correct. The fee is usually $200–$300. However, if you change tonnage, relocate equipment, modify ducts, add a heat pump where there was only AC, or upgrade from window units to central HVAC, the permit triggers a full plan review by the city's mechanical or energy consultant. Plan review adds 10-15 business days and a $250–$400 consultant fee. The city's online portal will route your application to the correct stream when you submit; do not assume it is a simple replacement until the portal tells you so.

Ductwork and air-sealing rules deserve special attention in San Carlos because the coastal climate (marine layer, cool nights, high humidity) relies on proper duct sealing to avoid energy waste and moisture problems. California Title 24 requires duct leakage testing if you install new ducts or modify more than 25% of the existing ductwork. The allowable leakage is 15% of design airflow (measured via blower-door or in-duct pressurization). If your system is in an unconditioned attic — common in San Carlos older homes — the city may require duct insulation R-8 minimum (Title 24 standard) and sealing at all joints with mastic or approved tape. If ductwork is buried in insulation or installed inside the building envelope, the inspector will verify compliance at the inspection. Many San Carlos homeowners are unaware that simply re-installing old ductwork without sealing or testing it violates the current code, even if it passed 20 years ago.

Refrigerant handling and EPA/CARB compliance add another layer. Any work involving the refrigerant charge (evacuation, recovery, top-up) must be performed by a technician certified under EPA Section 608 and compliant with California CARB regulations for ozone-depleting substances. If your old AC uses R-22 (common in pre-2010 systems), it is being phased out; replacement systems must use R-410A, R-32, or other approved low-GWP refrigerants. The permit application does not directly check EPA certification, but the licensed C-20 contractor is responsible. If you hire an unlicensed HVAC handyman to do the refrigerant work, you and he are both in violation. San Carlos Building Department will not approve the permit if the contractor's license is not current and in good standing; the city checks the Contractors State License Board (CSLB) database during permit issuance.

Three San Carlos hvac scenarios

Scenario A
Like-for-like AC replacement, 3-ton split system, same outdoor/indoor location, existing ducts reused — suburban San Carlos (Zones 3B coast)
You have a 15-year-old 3-ton AC unit failing (compressor noise, refrigerant leak). You want to replace it with a new 3-ton SEER2-16 unit from a licensed C-20 contractor, reusing the outdoor pad and indoor head location. The contractor pulls the permit via San Carlos's online portal, attaching a Title 24 Energy Commission Certificate of Compliance that documents the new unit's SEER2 rating, refrigerant type (R-410A), and confirmation that existing ducts will be cleaned and sealed with mastic at penetrations. Since you are not modifying ductwork and the tonnage is unchanged, the city codes this as a straightforward replacement. Permit is issued over-the-counter in 1-2 business days; fee is typically $200–$275 (1.5-2% of equipment cost for a $12,000–$15,000 installed system). No plan review is triggered. The contractor performs the work, the city inspector schedules a final inspection (usually within 2-3 days of notification), verifies nameplate data, checks refrigerant charge per the Title 24 CC, and approves. Total timeline: permit to final inspection, 7-10 calendar days. Cost: permit $200–$275 + contractor labor $1,500–$2,500 + equipment $6,000–$8,000 = $7,700–$10,775 total.
Over-the-counter permit | $200–$275 permit fee | No plan review | Title 24 CC required | Final inspection only | 7-10 day timeline | Existing ducts reused (cleaning & mastic sealing)
Scenario B
Heat pump installation replacing gas furnace + AC, new ductwork in attic, 4-ton capacity — foothills San Carlos (Zones 5B mountains), electrification retrofit
You are replacing a 30-year-old gas furnace and window AC with a new 4-ton cold-climate heat pump and relocating/resizing ducts to reach previously unconditioned zones. Existing ducts are inadequate and will be largely replaced. A licensed C-20 contractor is handling the project. This is NOT a simple replacement: new equipment, new/modified ductwork, increased capacity (implies a load calculation), and an electrification angle. The permit application triggers a full plan review. The contractor submits Title 24 CC plus duct design drawings showing attic installation, R-8 insulation, mastic sealing at all joints, and duct leakage testing protocol (blower-door method, 15% maximum allowable leakage). The city's mechanical/energy consultant reviews the design (10-15 business days) and issues a plan-review notice of approval or corrections. Consultant review fee: $250–$350. Permit fee: $350–$450 (2-3% of total project cost, which includes equipment ~$15,000 + labor $3,000–$5,000 + ductwork materials $2,000–$3,000). Once approved, contractor begins work. At rough-in (ducts installed but not sealed), city inspector performs duct leakage blower-door test. If leakage exceeds 15%, contractor remediates (additional sealing, $500–$1,500). Final inspection verifies refrigerant charge, thermostat, duct insulation R-value, and Title 24 compliance. Total timeline: permit application to final inspection, 25-35 calendar days. Cost: permit $350–$450 + plan review $250–$350 + equipment $15,000 + labor $4,000–$6,000 + ductwork $2,500–$4,000 = $22,100–$26,800 total.
Full plan review required | $350–$450 permit + $250–$350 consultant fee | Title 24 CC with load calc | Duct design plans required | Blower-door leakage test mandatory | 25-35 day timeline | R-8 attic duct insulation required
Scenario C
Mini-split heat pump addition (one head), 12,000 BTU, new outdoor unit on side of house, no ductwork — downtown San Carlos existing home (Zone 3B coast)
You want to add a single-zone ductless mini-split heat pump to a bedroom that is cold in winter. No ductwork involved; you are installing a new outdoor compressor on the side of the house and running refrigerant lines through the wall. A licensed C-20 contractor handles the install. This is a new HVAC addition (not a replacement) and triggers a permit, but it is not a full-system redesign. The contractor pulls a permit, attaching Title 24 CC for the single-zone unit (SEER2-18, HSPF2-8.5 for coastal San Carlos). Since there is no ductwork modification, no duct testing is required. However, because it is a new addition to the HVAC system, the city's plan reviewer will check that the outdoor unit placement complies with setback rules (usually 3-5 feet from property line in San Carlos residential zones) and that refrigerant line routing does not violate building height or easement rules. Plan review is light but required: expect 5-7 business days and a $150–$200 consultant fee. Permit fee: $175–$250. The contractor performs the installation, and the city inspector checks: outdoor unit clearances, refrigerant charge per Title 24 CC, electrical connection (if the unit has a 240V outlet, an electrician may be required separately), and thermostat. No duct leakage test. Final inspection typically 3-5 days after rough-in notice. Total timeline: permit to final, 10-15 calendar days. Cost: permit $175–$250 + plan review $150–$200 + equipment $3,500–$5,000 + labor $1,000–$1,500 = $4,825–$6,950 total.
New HVAC addition (not replacement) | $175–$250 permit + $150–$200 plan review | Title 24 CC for single-zone unit | No ductwork (duct test not required) | Setback compliance check required | 10-15 day timeline | Final inspection verifies refrigerant charge & thermostat

Every project is different.

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San Carlos coastal climate and HVAC sizing: why marine-layer strategy matters

San Carlos straddles California Climate Zones 3B-3C on the coast and extends into Zones 5B-6B in the foothills. The coastal zone (where most residents live) has mild winters and cool summers, with the marine layer providing free cooling most nights and summer afternoons. This climate profile means HVAC systems are often oversized by contractors accustomed to inland California practice, leading to short-cycling, poor humidity control, and energy waste. Title 24 requires load calculations (ACCA Manual J or equivalent) for new systems, but many contractors skip detailed analysis if replacing a similar-capacity unit. San Carlos Building Department's plan reviewers often flag oversized heat pumps on the coastal end of town. If your load calc shows a 3-ton unit is adequate, but the contractor specs a 4-ton to 'be safe,' the city may reject the plan review or require downsizing. This is not arbitrary: marine-layer climates benefit from right-sized units that dehumidify effectively without cycling on and off.

The practical upshot for your project: if you are in downtown San Carlos or near the Bay shoreline, ask your contractor to run a detailed Manual J load calc using actual winter/summer design temperatures (San Carlos winter design is ~35°F, summer design ~75°F outdoor). Supply that to the city with your permit application. If you are in the foothills (Zones 5B-6B), heating loads are more significant and oversizing is less of a concern, but cooling must account for lower humidity. The city's plan reviewers know the zones well; they will catch an obvious mismatch. Getting the load calc right before permit submission saves plan-review delays and potential rejections.

Duct location and sealing strategy also pivots on marine-layer reality. Attic ducts in San Carlos coastal homes can be problematic because cool marine air infiltrating the attic through vents can cool the ducts excessively, causing condensation and mold risk. The city now requires attic duct insulation R-8 minimum and strict sealing at all penetrations. If you are running ducts through the attic, expect the inspector to carefully examine insulation coverage and check for any evidence of prior condensation. In foothills homes with warmer attics, this is less critical but still required by code.

Title 24 Energy Commission Certificate of Compliance: what it is, why it matters, and how to avoid costly rejections

The Energy Commission Certificate of Compliance (CC) is a one-page form (Form NCHCP or equivalent) completed and signed by a licensed C-20 contractor or energy consultant, documenting that the HVAC system meets current Title 24 efficiency standards. It is not a permit itself; it is a prerequisite document that the Building Department requires before issuing a permit. Many homeowners and even some smaller contractors confuse this step. You cannot apply for an HVAC permit without a CC attached. The CC must specify: equipment model numbers, SEER2 rating (or SEER for older baselines), HSPF2 rating (for heat pumps), refrigerant type, duct leakage allowance if applicable, thermostat type, and the contractor's signature and C-20 license number.

San Carlos Building Department's online portal has a checklist for HVAC permits. If the CC is missing, incomplete, or signed by someone without a C-20 license, the permit application is automatically rejected with a request to resubmit. This is not a minor inconvenience: rejected applications cause 1-2 week delays while the contractor obtains or corrects the CC. To avoid this, before you submit a permit application, have your contractor provide a draft CC and review it for completeness. Verify the contractor's C-20 license number against the CSLB website (check.cslb.ca.gov). If the contractor says 'I'll submit the CC after you get the permit,' stop and ask for the CC in writing first. The city will not issue a permit without it, and you will lose time.

Title 24-2022 standards (current as of early 2024) require SEER2-16 minimum for AC in San Carlos coastal zones (Climate Zone 3B-3C) and SEER2-14-16 in foothills zones. Heat pumps must achieve HSPF2-8.0 or higher in coastal zones, HSPF2-7.5 in foothills. These are roughly 20-30% more efficient than 2019 standards, so older equipment estimates may not meet current code. If a contractor quotes equipment from 2020-2021 leftover stock with lower SEER2 ratings, it will not be approvable. Always confirm equipment is 2024-current and rated for Title 24-2022 compliance.

City of San Carlos Building Department
San Carlos City Hall, San Carlos, CA (exact street address and permit office location should be verified via city website)
Phone: Contact City of San Carlos main line and ask for Building and Planning Department, or search 'San Carlos CA building permit' for direct line | San Carlos city website — look for 'Permits' or 'Online Services' to access the permit application portal and fee schedule
Monday–Friday, 8:00 AM–5:00 PM (standard municipal hours; verify for current holiday closures)

Common questions

Can I hire any HVAC contractor, or does it have to be someone licensed in California?

The contractor must hold a current California C-20 (HVAC) license issued by the Contractors State License Board (CSLB). Unlicensed HVAC work is illegal in California and violates San Carlos municipal code. Verify the contractor's license on check.cslb.ca.gov before hiring. If the contractor's license is expired, suspended, or inactive, the city will reject the permit application. Do not proceed with work unless the license is active and in good standing.

I'm replacing my AC with the exact same model. Do I still need Title 24 certification?

Yes. Even a like-for-like replacement requires Title 24 Energy Commission Certificate of Compliance. The city must verify that the new equipment meets current standards (even if it is the same model as the old one, the new unit's nameplate rating is documented). Your contractor will provide the CC with the new unit's serial number and SEER2 rating. Without it, the permit is rejected.

What if my HVAC contractor is licensed in another state but wants to work in San Carlos?

He cannot. California does not accept out-of-state HVAC licenses. A contractor must hold a California C-20 license. If he is licensed in Nevada or another state, he must apply for a California license before beginning work. San Carlos Building Department will not issue a permit to an out-of-state-licensed contractor. This is a statewide rule, not a local San Carlos exception.

Do I need separate permits for electrical work (e.g., a new 240V outlet for a heat pump)?

Possibly. If your heat pump requires a dedicated 240V circuit (most do), an electrician will install that outlet. The electrician pulls a separate electrical permit through San Carlos Building Department. The HVAC permit covers the heat pump and refrigerant lines; the electrical permit covers the outlet and circuit. Coordinate with your contractor to ensure both are scheduled and final-inspected.

What happens during the final HVAC inspection? What does the inspector check?

The city inspector verifies: equipment nameplate data (model, serial number, SEER2 rating) against the Title 24 CC, refrigerant charge amount and type, duct sealing and insulation (if ducts were modified), blower operation, thermostat response, and indoor/outdoor unit placement for code compliance. The inspection typically takes 30–60 minutes. Be present if possible to answer questions. Once the inspector approves, you receive a permit closure notice and may operate the system.

I want to do my own HVAC work to save money. What are the rules in California and San Carlos?

California B&P Code § 7044 allows owner-builder HVAC only if YOU personally hold a current C-20 license, or you employ a C-20 license holder as your responsible managing employee (RME). Most homeowners do not hold this license. If you lack the C-20 license and attempt HVAC work, you are in violation of state law, and San Carlos will not issue a permit. Hire a licensed contractor to handle refrigerant and sealing work; you cannot save money by doing HVAC yourself unless you are a licensed professional.

How much does an HVAC permit cost in San Carlos?

Permit fees range $150–$450 depending on system size and scope. A simple replacement of a 3-ton unit typically costs $200–$275. New installations or system redesigns cost $300–$450. Plan review (required for new systems or major modifications) adds $150–$400. Total permit and review costs are usually $200–$850. Your contractor will quote the exact fee once the project scope is clear. The city's online portal displays the current fee schedule.

What is a duct leakage test, and when is it required?

A duct leakage test (using a blower door or in-duct pressurization) measures air escaping from the ductwork. California Title 24 requires it if you install new ducts or modify more than 25% of existing ducts. Allowable leakage is 15% of design airflow. The test is performed during the rough-in phase (ducts installed but not yet sealed). If leakage exceeds the limit, the contractor remediates (adds sealing, retests). Cost for testing is typically $200–$400 and is included in the contractor's estimate. If you reuse existing ducts without modification, no test is required.

Can I install a heat pump if my house has a gas furnace and I want to keep the furnace as a backup?

Yes, you can install a heat pump as a primary heating/cooling system and retain the gas furnace for emergency backup. San Carlos code permits dual-fuel or backup systems. However, if the backup furnace remains connected to active gas lines, the gas system and furnace are still subject to code inspection. The heat pump counts as a new HVAC system and requires Title 24 CC and a permit. The furnace is regulated separately. Discuss your backup strategy with your HVAC contractor and gas inspector to ensure all systems are code-compliant and safely interlocked (so they don't both run simultaneously).

My home is in the San Carlos foothills (Zone 5B). Are HVAC rules different from downtown?

Not significantly, but climate-zone-specific design parameters differ. Foothills homes (Zones 5B-6B) have colder winters and warmer summers, so heating loads are higher and cooling loads may be lower than coastal homes. Title 24 requires load calculations that account for zone-specific design temperatures. A contractor should run Manual J using the correct foothills design temps (San Carlos foothills winter design ~20–30°F, summer ~85–90°F depending on elevation). Title 24 efficiency minimums are SEER2-14 for cooling (vs. 16 coastal) and HSPF2-7.5 (vs. 8.0 coastal), reflecting lower cooling demand. Otherwise, permit procedures and inspection requirements are identical. Plan review happens either way.

Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current hvac permit requirements with the City of San Carlos Building Department before starting your project.

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