What happens if you skip the permit (and you needed one)
- San Carlos Building Enforcement will issue a stop-work order (typically within 2–6 weeks of a complaint) and levy a $500–$1,500 penalty, plus demand you pay DOUBLE the original permit fee ($1,000–$1,500) to legalize the system retroactively.
- Your homeowner's insurance may deny a claim related to the roof or electrical fire if the solar system was installed without a permit — a common denial trigger if a fire starts near the array.
- California Residential Transfer Disclosure (TDS) requires you to disclose unpermitted work to the next buyer; this kills buyer confidence and drops your home's value by 3–8% ($30,000–$80,000 on a $1 million home).
- Peninsula Clean Energy will not register your system for net metering credits without proof of final electrical inspection and city sign-off — unpermitted systems generate zero revenue and zero solar credits, making ROI impossible.
San Carlos solar permits — the key details
San Carlos Building Department requires ALL grid-tied photovoltaic systems to be pulled through two separate permits: a Building Permit (for the mounting, roof attachment, and structural load) and an Electrical Permit (for the inverter, disconnect, conduit, grounding, and NEC Article 690 compliance). The Building Code adopted is the 2022 California Building Code (based on 2021 IBC), which incorporates NEC Article 690 by reference. For systems mounted on an existing roof, the city triggers a mandatory Roof Structural Evaluation if the PV array exceeds 4 pounds per square foot of projected roof area; most residential systems are 3–4 lbs/sq ft, so this threshold is regularly hit. A structural engineer must stamp the evaluation certifying the roof can handle the combined dead load (panels, racking, snow, wind). San Carlos' specific requirement, detailed in the city's solar permit checklist (available at city hall or their online portal), mandates that all structural evaluations use the 2022 California Building Code snow load maps, which classify most of San Carlos coastal areas as Zone 3 (25 psf) and upland areas as Zones 4–5 (up to 60 psf in the hills). Applicants who use generic national snow-load software often submit non-compliant evaluations and trigger a staff rejection loop — a single rework adds 1–2 weeks.
The second critical gate is the Peninsula Clean Energy (or PG&E) interconnection application, which must be substantially complete BEFORE the city will sign off. NEC 705 (Interconnected Electric Power Production Sources) and PG&E's and Peninsula Clean Energy's Interconnection Procedures both require proof of utility review and written confirmation that the proposed system meets IEEE 1547 anti-islanding and voltage-ride-through standards. San Carlos Building Department staff will check the utility application status during plan review and will not issue a permit until that application is acknowledged as received. This is the single most common cause of permit delays in San Carlos — homeowners are rejected once, resubmit to the city, but forget to follow up with the utility, and then the city rejects them again. The utility's Interconnection Study (if required for your system size) can take 15–30 days; fast-track studies for small residential systems (under 15 kW) are often waived, but you must explicitly request it and confirm the waiver in writing.
NEC 690.12 (Rapid Shutdown of PV Systems on Buildings) is now California-wide law and is enforced in San Carlos. All rooftop PV systems must have a listed rapid-shutdown controller that cuts DC voltage to the array to ≤30 V within 3 seconds of loss of AC power. San Carlos' plan checkers verify the controller is specified on the one-line diagram and that the controls drawing shows the shutdown wiring path. String-inverter systems are common in residential installs, and the rapid-shutdown requirement means you cannot simply hardwire the DC string — you must either use microinverters (which inherently meet this), install a DC-side rapid-shutdown module (like a SafetyLink or Yaskawa controller), or use an AC-coupled battery system with inverter-integrated shutdown logic. Failure to specify rapid-shutdown in your electrical plan results in an automatic rejection; this is the #2 reason for resubmissions in San Carlos (after the utility interconnection gate).
San Carlos has adopted California's AB 2188 fee-cap rules, which limit residential solar permits to $500–$750 for the building permit (capped at 0.4% of the system's installed cost, not to exceed $750). The electrical permit is NOT capped and typically runs $200–$400 depending on system complexity and conduit runs. If you add battery storage (ESS, energy storage system), the Fire Marshal conducts an additional review (required for any battery system over 20 kWh or with specific chemistries), which adds $150–$300 and 1–2 weeks. The city's online portal (https://www.sancarlosca.gov/building-permits, or contact the Building Department for the exact URL if using a third-party service) allows electronic submission of drawings, structural reports, and the utility interconnection letter, which accelerates review compared to paper submissions.
Inspection sequence for a typical residential PV system in San Carlos is (1) Roof/Structural Inspection (verifies racking is bolted per engineer specs, no roof penetrations in wrong locations, flashing is installed correctly), (2) Electrical Rough Inspection (verifies conduit is run, disconnect switches are accessible, rapid-shutdown wiring is in place, inverter is mounted and labeled), and (3) Final Electrical Inspection (tests continuity, verifies bonding, confirms labeling matches the one-line diagram). The utility then conducts a witness inspection during the final phase to confirm anti-islanding and metering are functional. Total inspection time is typically 3–4 weeks from permit issuance to final approval, assuming no rejections. Owner-builders are allowed to pull permits in San Carlos under California Business & Professions Code § 7044, but the ELECTRICAL portion must be performed by a licensed electrician (C-10 or C-7 contractor); you cannot self-perform the electrical work. Many owner-builders hire the electrician to pull the electrical permit in their name and the homeowner pulls the building permit — this is a common legal structure.
Three San Carlos solar panel system scenarios
San Carlos' two-permit structure and why the utility interconnection gate blocks city approval
San Carlos Building Department does not issue a Certificate of Occupancy or permit approval until the utility (Peninsula Clean Energy or PG&E) confirms in writing that an Interconnection Application is filed and has received a Fast-Track Study approval (for systems under ~15 kW) or a standard Interconnection Study completion (for larger systems). This is not optional; it is explicitly embedded in the city's solar permit checklist and the plan reviewer's approval workflow. The reason is that NEC 705 and California Title 24 (Energy Code) both mandate that the local AHJ (Authority Having Jurisdiction, in this case San Carlos Building Department) cannot authorize grid connection without proof that the utility has reviewed the system for IEEE 1547 anti-islanding and voltage ride-through compliance. Many homeowners and contractors assume the utility review happens AFTER the city signs off; in San Carlos, that assumption kills the permit.
Peninsula Clean Energy is the aggregated community choice energy provider serving most of San Carlos (excluding some PG&E-service-only pockets; check your bill). Peninsula Clean Energy's Interconnection Procedures require an online or paper application (Form 79-1066 or equivalent), proof of system design (one-line diagram), and the proposed inverter model number and UL certification. For a 5 kW residential system, the Fast-Track Study is usually issued within 5–10 business days, and there is no additional engineer review or site inspection required — the utility's automated system checks anti-islanding specs and confirms your inverter is on the approved list. If you have a battery (ESS), the study becomes standard (not Fast-Track), and the utility will run a more detailed analysis to confirm the battery charger/inverter meets interconnection rules; this can take 15–30 days. If you fail to submit the interconnection application, the city will issue a Conditional Use Permit or a Notice of Violation (depending on how long you've waited) and will not activate net metering.
Contractors often handle the utility application as part of their service, but homeowners must confirm this in the contract. A common mistake is the contractor submits to the city but forgets to submit to the utility simultaneously, so the city approves the permit in 10 days, but the contractor has not yet filed with the utility. The homeowner thinks they are done, orders panels, and then the utility denies net metering registration 6 weeks later because the interconnection study was never completed. San Carlos staff can issue a verbal approval after the city plan check is done, but they will NOT issue a written permit until the utility letter is attached. This verbal approval does not allow you to begin work — you must have the written permit in hand. The sequence is: (1) Utility application submitted, (2) City permit application submitted (attach a PDF of the utility app or utility confirmation email), (3) City plan review, (4) City issues Conditional Approval pending utility study, (5) Utility Fast-Track issues (10 days typical), (6) Homeowner or contractor submits utility letter to city, (7) City issues Final Permit Approval. Total process: 3–4 weeks if everything is parallel. If utilities are sequential (you wait for city, then submit to utility), total process: 4–6 weeks.
NEC 690.12 rapid shutdown, San Carlos plan review reality, and why string-inverter systems require a separate DC-side shutdown module
Rapid Shutdown of PV Systems on Buildings (NEC 690.12) became California law statewide in 2017 and is now a non-negotiable requirement for any rooftop system in San Carlos. The rule requires that loss of AC power (grid outage or intentional disconnect) brings the DC voltage at the PV array to ≤30 V within 3 seconds. This is a safety rule designed to protect firefighters and first responders who may be inside the building during a fire — if the DC voltage is low, there is less risk of arc flash or electrocution. The challenge is that string-inverter systems (which are the most common residential topology because they are cheapest) do NOT inherently meet this rule. A string inverter sits at the base of the roof, and the DC wires from the array simply run into it; if the inverter shuts down, the panels are still energized at 250–400 V DC during daylight.
San Carlos' plan checkers verify rapid shutdown compliance in the electrical one-line diagram. They look for one of three solutions: (A) Microinverters (each panel has its own inverter, so DC voltage is only 40–60 V per microinverter, already ≤30 V), (B) AC-coupled battery system with a integrated rapid-shutdown inverter/charger that cuts DC circuits when the AC bus is de-energized (Tesla Powerwall, Generac PWRcell, etc.), or (C) a DC-side Rapid Shutdown Controller (SafetyLink, Yaskawa Solectria, or equivalent) that sits in the DC circuit and uses a dry-contact signal from the inverter to open a contactor and dump the DC voltage. If you submit a plan with a string inverter and no rapid-shutdown solution, the plan checker will reject it with a note like 'NEC 690.12 compliance not specified' or 'Rapid shutdown method required — submit revised one-line diagram.' A rework takes 2–5 days (you contact the contractor, they add a SafetyLink module to the design, you resubmit), and then another 5–7 days for re-review. This is the #2 rejection reason in San Carlos (after utility interconnection gate).
Microinverters are the fastest way to clear NEC 690.12 for San Carlos because the approval is automatic — no box to add, no new conduit runs, no additional cost (microinverters are ~$1,000–$2,000 more expensive than a string inverter + optimizer combo, but the rapid-shutdown controller would cost $800–$1,200 anyway). A plan that shows 20 microinverters (one per panel) with a Sunny Boy or Enlighten monitoring system gets a nod in 1–2 days. The trade-off is that microinverters have higher marginal cost per watt, so a string inverter + rapid-shutdown module system may be cheaper on a very large system (20+ kW), but for most residential systems (3–8 kW), microinverters are cost-neutral or cheaper when you factor in the designer time and re-plan costs. San Carlos' expedited solar track (SB 379, ~2-week turnaround) assumes microinverters or battery-based systems because they have fewer review gates.
600 Elm Street, San Carlos, CA 94070 (or check city website for current address)
Phone: (650) 802-4200 (main number; building permit line may be separate — confirm) | https://www.sancarlosca.gov/building-permits (or contact Building Department for current online portal URL if using third-party system)
Monday–Friday, 8:00 AM–5:00 PM (Pacific time; verify for holidays and expedited permit hours)
Common questions
Can I get a permit approval in less than 2 weeks in San Carlos?
Yes, under SB 379 expedited review, San Carlos targets 10 days for complete, compliant solar permit applications. The key is submitting an error-free application the first time: structural eval (if needed) signed by PE, rapid-shutdown method clearly shown on one-line diagram, and proof of utility interconnection application (or utility confirmation email). If your plan is perfect and the utility Fast-Track issues within 5 days, you can have a permit in hand in 10–12 days. If there are deficiencies (missing structural eval, no rapid-shutdown spec, no utility app), plan for 3–4 weeks.
Do I have to use Peninsula Clean Energy, or can I use PG&E?
Depends on your address. Most of San Carlos is served by Peninsula Clean Energy (a community choice aggregator), but some areas (especially south and east foothills) are still PG&E-only service. Check your electric bill or call your current provider. If you are in the PG&E service area, you submit your interconnection application to PG&E, not Peninsula Clean Energy. The city's permit process is the same either way — the AHJ still requires proof of utility application in the building permit file.
What if my roof is too old to support a solar system?
The structural engineer's evaluation will determine this. If the engineer concludes the roof cannot safely support the additional load (especially if composition shingles are deteriorated or decking is rotten), you have two options: (1) Re-roof the home first (can add $8,000–$15,000), which resets the roof's lifespan and allows solar to proceed, or (2) mount the system on the ground (if you have space) to bypass the roof load question. San Carlos has no specific requirement to re-roof before solar, but the engineer's stamp is final — you cannot work around a failed evaluation.
Does San Carlos require a battery backup system, or is grid-tied only an option?
Grid-tied only is standard and is what the vast majority of San Carlos residents choose. A battery system is optional and adds cost ($8,000–$15,000 for a 10 kWh system) and a third permit gate (Fire Marshal review). You do NOT need a battery to get solar approved in San Carlos. If you want battery later, you can add it after your grid-tied system is operating — the city can issue a separate permit for a retrofit battery add-on.
If my home is in a historic district, do I need Design Review approval before I can get a solar permit?
It depends on whether your specific address is zoned within the historic district overlay. Contact San Carlos Planning Department to confirm. If yes, you will need an Architectural Review Committee (ARC) Design Review approval before the Building Department will issue a solar permit. For residential solar, this is often expedited (ministerial approval, no hearing) and takes 10–15 days. If ARC denies the design (e.g., wants black modules instead of silver to blend with roof), you can appeal or modify the design. Always check historic zoning BEFORE you hire a contractor — it can add 2–4 weeks.
Who performs the roof structural evaluation, and how much does it cost?
A licensed structural engineer (PE stamp required) performs the evaluation. They will review the roof framing plans (if available from your home's original permits) or may conduct a visual inspection and age assessment, then calculate whether the proposed racking load plus snow and wind loads are within the roof's design capacity. Cost is typically $400–$700 in San Carlos. If your home is old (pre-1960s) or the original plans are unavailable, the engineer may recommend a more detailed inspection (adding $200–$300). The structural report is required for all systems over 4 lbs/sq ft and is strongly recommended for any system on an older roof.
What happens during the final inspection, and do I have to be home?
Final Electrical Inspection is conducted by San Carlos Building Department electrical inspector (not your electrician). The inspector verifies continuity testing of all DC and AC circuits, confirms all labeled breakers and disconnects match the one-line diagram, checks bonding to the service ground, and verifies the inverter's anti-islanding certification label is visible. Your contractor (or a representative) must be present. The utility (Peninsula Clean Energy or PG&E) may also send an inspector on the same day or the next day to witness the final test and confirm the revenue-grade meter and net metering setup. If everything passes, the city issues a Notice of Final Approval the same day or next business day, and the utility activates net metering within 1–2 weeks.
Can I install solar panels myself if I own the home?
You can pull the Building Permit as an owner-builder under California law (B&P Code § 7044), but you CANNOT perform the electrical work yourself. The Electrical Permit MUST be pulled and signed by a licensed electrician (C-10 General Electrician or C-7 Solar contractor). The racking, roof attachment, and all mechanical work can be owner-performed, but the moment DC or AC circuits are connected, a C-10 licensed electrician takes over. This means if you are cost-cutting, you might save $1,000–$2,000 on the racking labor, but the electrician's labor + permit costs $3,000–$5,000 regardless. Many San Carlos DIY homeowners hire the electrician to pull the electrical permit and work, then handle the building permit and racking coordination themselves.
Will my solar permit cost the same if I get a second quote from a different installer?
No. Permit FEES are set by the city and are the same (capped at $650–$750 for residential building permits under AB 2188), but the engineering and design COST varies by installer. A low-cost installer may use a one-size-fits-all roof design and generic structural eval ($400), while a custom-design installer may do a site-specific wind analysis for hilltop homes and charge $600–$800. Both are valid; the difference is in the engineering rigor and timeline. The city's plan reviewer will scrutinize the engineering, so a cheap engineer's report may trigger rejections and rework, costing you more in time.
How long after my final inspection can I start using the solar power for net metering credits?
After final inspection approval (same day), your installer will contact the utility to schedule a witness inspection and meter swap (activation of net metering). Typically, the utility completes this within 3–5 business days. The system generates power immediately after final inspection, but it will not be credited toward your bill until the utility's net metering registration is complete — usually within 1–2 weeks total. During this gap, you are generating power but not receiving credits; the credits are back-paid once net metering is activated.