What happens if you skip the permit (and you needed one)
- Unpermitted installation voids your system warranty and disqualifies you from PG&E net-metering credits ($100–$300/year in lost revenue on a 5 kW system) — the utility will not interconnect a system without proof of final inspection.
- PG&E will refuse to upgrade your service panel or install a bi-directional meter until permits are pulled and final inspection is passed; delay costs $2,000–$5,000 if you must hire a licensed electrician retroactively to troubleshoot code violations.
- County assessor's office flags unpermitted solar as a code violation during resale; California Real Estate Transfer Disclosure Statement now requires solar disclosure, and buyers' insurance will require prior-written approval (often denied) — expect 5–10% price reduction or deal collapse.
- City enforcement (complaint-driven) leads to a $100–$500 daily fine plus demand for removal and re-permitting; structural damage to roof undetected in skipped inspection can cost $15,000–$40,000 to remediate after leaks develop.
Los Altos solar permits — the key details
Los Altos Building Department issues two distinct permits for any grid-tied solar system, regardless of size. The Building Permit covers the mounting structure, roof-attachment hardware, and structural adequacy of the roof to carry the load (typically 3–5 lb/sq ft for modern panels). The Electrical Permit covers the inverter, DC conduit, AC disconnect, grounding, and interconnection to the main panel or sub-panel. Per NEC Article 690 (Photovoltaic Systems), every PV system requires labeled disconnects, proper grounding per NEC 250.166, rapid-shutdown equipment per NEC 690.12, and conduit fill not exceeding 40% per NEC 310.15(B)(3)(a). Los Altos requires both permits to be finalized (with inspections passed) before PG&E will activate net metering. The city does not offer a single consolidated solar permit; you will have two permit fees and two separate plan-review timelines, though they can be processed in parallel.
Plan review timeline in Los Altos is typically 5–10 working days for straightforward projects (roof-mounted, no battery, under 10 kW), but can extend to 3–4 weeks if the roof structural evaluation is incomplete or if the inverter/disconnect layout requires back-and-forth revision. Per the California Building Code Section 108.2, the Building Official must have a California-licensed structural engineer's report if the roof loading exceeds 4 lb/sq ft; most residential solar arrays sit under this threshold, but older or wood-frame homes in Los Altos foothills may trigger additional scrutiny. Los Altos does not currently participate in California's SB 379 same-day permit program for solar (which allows instant issuance of expedited permits in some jurisdictions if plans meet pre-set criteria), so expect full review. However, if your plans are complete, clear, and use a pre-approved inverter + mounting system, the Electrical Permit may be issued over-the-counter in as little as 1–2 days.
PG&E interconnect application is a mandatory third step and must be submitted before or concurrent with the electrical permit application. The utility will issue an Interconnection Study Agreement (ISA) and perform a feasibility study, which typically takes 10–30 days. You cannot legally energize a grid-tied system without PG&E's written approval and activation of your net-metering account. PG&E Form 79-1450 (or its successor form per Rule 21) requires your system details (kW capacity, inverter model, proposed breaker size) and proof that the interconnection point is safe for both utility workers and homeowners. Los Altos Building Department will not issue a final certificate of occupancy/electrical final permit until you provide proof that PG&E has accepted your interconnection application (some inspectors require the final written approval, not just the application receipt). This sequencing is critical: file the interconnect application first, or simultaneously with permits, not after.
Permit fees in Los Altos for solar are calculated as a percentage of project valuation per the city's 2024 Fee Schedule. A typical 5 kW roof-mounted system (valued at $12,000–$15,000 installed) will generate approximately $300–$500 in combined building and electrical permit fees. The city charges roughly 1.5–2% of valuation for residential electrical permits and 1–1.5% for building permits, subject to a minimum. Battery storage systems add complexity: a 10 kWh battery ESS (e.g., Tesla Powerwall) triggers a separate Fire and Life Safety permit in many Bay Area jurisdictions, though Los Altos has not yet adopted a specific Fire Code amendment for residential ESS under 20 kWh. Verify with the Fire Marshal's office if your project includes batteries. Expedited or over-the-counter electrical permits (if available) may waive some fees or allow same-day issuance; call the Electrical Inspector at Los Altos Building Department to confirm current practice.
Inspections occur in three stages: (1) Structural/Roofing — inspector verifies proper flashing, fastener spacing per manufacturer specs, and roof condition; (2) Electrical Rough — verifies conduit, DC disconnect, grounding electrode, surge arrestor, and string inverter or micro-inverter installation before final cover-up; (3) Electrical Final — verifies AC breaker integration, utility interconnect disconnect, labeling, and readiness for utility witness test. PG&E will also conduct a final witness inspection of your bi-directional meter installation, which is NOT part of the city permits but is required before net-metering service begins. The entire process from permit application to utility energization typically takes 3–8 weeks in Los Altos, depending on plan completeness and utility scheduling. Owner-builders may perform the work themselves (per California Business and Professions Code Section 7044) if they own the property, but the electrical work must still be inspected and approved by a licensed electrical contractor or must be signed off by the licensed electrician who pulls the permit.
Three Los Altos solar panel system scenarios
Los Altos roofing and structural code for solar: why your roof inspection takes time
Los Altos Building Department enforces the 2022 California Building Code Section 1510 (Solar Photovoltaic Systems) and IRC R324, which require structural verification that the roof can support both the dead load of the panels (typically 2.5–4 lb/sq ft) and the additional wind and seismic loads imposed by the racking. The city is in Seismic Design Category D (per USGS data for the San Francisco Bay region), which means roof-attached solar systems must be designed for seismic forces in addition to wind (IBC 12.13.3). For systems under 4 lb/sq ft on typical wood-frame residential homes, the Building Official may waive the requirement for a California-licensed structural engineer's report and instead accept the mounting manufacturer's standard calculation sheet (which shows compliance with IBC 1609 wind load and Seismic Design Category D). However, if the roof is tile, slate, metal-standing-seam, or if the home has a flat roof, the inspector will likely ask for an engineer's report because these roof types have different fastening rules and less margin for concentrated loads.
Los Altos is in the foothills and coastal transition zone, which means roofing conditions vary widely. Homes in the Los Altos Hills (west side) often have old cedar or asphalt shingles with poor attic ventilation and may have rotten sheathing; the inspector will note this and may require sheathing replacement before permits are approved. Homes on the flat, coastal side (east toward Palo Alto) have more modern roofs (asphalt shingles 2000s-era or newer asphalt/metal), which typically pass without issue. Frost depth in the foothills is 12–18 inches, which affects any ground-mounted arrays (require frost-line footer depth). The Building Code requires roof flashing to meet the International Building Code Section 1507 (Roofing Assemblies and Rooftop Structures) and must be sealed per manufacturer specs for the specific roof type. If your system includes a roof penetration for conduit, the inspector will verify that the boot is sealed with UL-rated sealant and that the penetration does not violate the roof warranty. Many roofers require that solar mounting be installed by the solar contractor, not the electrician, to preserve the roof warranty.
The structural trigger of 4 lb/sq ft is important: it is the threshold below which a California Building Official may accept a manufacturer's design sheet without a full PE-stamped report. A typical modern solar panel is 350 W, measuring 77 inches x 39 inches x 1.4 inches, weighing about 42 pounds. With aluminum racking, each panel-plus-racking weighs approximately 70 pounds, or about 2.3 lb/sq ft for a 15-panel 5 kW system on a 1,200 sq ft roof section. Most residential systems stay under 4 lb/sq ft, but a densely packed 10 kW system on a small roof section could exceed it. When the design exceeds 4 lb/sq ft, Los Altos will require a California-licensed structural engineer to review roof framing, decking, fastening, and connections per the 2022 California Building Code Chapter 32 (Encroachments into Public Right-of-Way) does not apply to rooftop solar, but Chapter 4 (Foundations) applies to ground-mounted arrays and requires proper frost-line footings and soil bearing capacity verification.
Roof inspection occurs before the electrical rough inspection. The Building Inspector will verify: (1) that the roof surface is sound and not leaking (walk-around inspection or prior roofer certification), (2) that mounting rails are fastened per manufacturer specs and building code (typically 16 inches on-center maximum for residential roof decking), (3) that flashing is installed and sealed, (4) that no roof penetrations (conduit entries) lack proper boots or sealant, (5) that the system is set back appropriately from roof edges and parapets per IBC 1511. For tile roofs, the inspector will require that individual tiles be removed and the racking bolted through the decking, not just resting on tiles. For metal roofs, fastening rules differ and may require special clamps to avoid roof perforation. Once the roof inspection passes, you receive sign-off (usually within 1 business day of request) and can proceed to electrical rough inspection.
PG&E net-metering and interconnection sequencing in Los Altos: why you can't skip the utility step
Los Altos is served entirely by Pacific Gas and Electric (PG&E) under California's net-metering rules (currently Net Energy Metering Version 3, or NEM 3.0, effective April 2023 for new systems). PG&E interconnection is not a Los Altos city requirement but a utility and state requirement that the city's Building Official will enforce by refusing to issue a final electrical permit without proof of a filed interconnection application or approved agreement. PG&E requires you to submit Form 79-1450 (Application for Interconnection of Distributed Energy Resources, or ADER) or its successor form before the utility will schedule a feasibility study. The form asks for your PV system size (kW), inverter model and ratings, proposed interconnection point (main breaker or sub-panel), and an electrical single-line diagram showing breaker size, disconnect location, and grounding details. PG&E will not simply wave through a form; the utility studies the system to ensure it will not cause voltage rise, harmonic distortion, or backfeed risk to neighboring customers or utility equipment.
The interconnect study timeline is 10–30 days depending on PG&E's queue. In 2024, PG&E's application backlog is significant (many studies take 4–6 weeks), but the utility provides a tracking number and status updates online. Importantly, you can file the interconnection application before the city approves your permits; in fact, Los Altos Building Department recommends filing the PG&E application in parallel with your city permit application. The sequence is: (1) obtain PG&E Form 79-1450, (2) have your solar installer fill it out with system specs, (3) submit to PG&E, (4) file building + electrical permits with the city, (5) city reviews and calls for missing docs, (6) PG&E completes feasibility study and issues approval, (7) city issues final electrical permit contingent on PG&E approval, (8) you schedule inspections, (9) city conducts inspections, (10) PG&E witness test and meter installation. If you do NOT submit the PG&E application in step 3, steps 4–7 will stall because the city will not sign off on the electrical permit without proof of PG&E acceptance.
Net metering under NEM 3.0 is less generous than prior versions: PG&E now credits excess solar generation at the avoided-cost rate (typically $0.05–$0.10 per kWh, much lower than the retail rate of $0.20–$0.35 per kWh depending on time-of-use period). Many Los Altos homeowners are surprised to learn that their payback period has extended from 5–7 years to 8–12 years compared to NEM 2.0. Battery storage (like a Powerwall) does NOT qualify for net metering; instead, battery charge/discharge is metered separately, and the homeowner must manage when to charge and discharge manually or via software to maximize self-consumption and minimize purchases from the grid. PG&E will install a bi-directional meter (e.g., Landis+Gyr OpenWay 3500 or successor) at no charge if you are a net-metering participant, but the installation is PG&E's responsibility and is coordinated after the city's final electrical inspection passes.
For hybrid systems with battery storage, the PG&E interconnection application is more complex. You must declare the battery rating (kWh and kW output), the battery's charge/discharge strategy (manual or automatic via battery management software), and how the battery interfaces with the main panel. PG&E may require a separate three-line diagram showing: (1) PV + Inverter → Battery → Load/Grid, (2) AC Main Breaker, (3) Battery Disconnect. Some battery systems (like Tesla Powerwall with Backup Gateway) require a separate 200-amp sub-panel and second meter if you want grid-interactive operation; others (like Generac PWRcell) can integrate into the main panel with proper breaker coordination. Los Altos Building Department will require the battery manufacturer's technical data sheet and PG&E's written approval before the electrical permit final is issued. This is where Scenario B takes longer: the combined city + utility review for a hybrid system typically adds 2–3 weeks to the overall timeline.
Los Altos City Hall, 1 North San Antonio Road, Los Altos, CA 94022
Phone: (650) 947-2700 | https://www.losaltosca.gov/building-division
Monday–Friday, 8:00 AM–5:00 PM (verify hours at losaltosca.gov)
Common questions
Can I install solar myself in Los Altos if I own my home?
Partially. California law (Business and Professions Code Section 7044) allows owner-builders to perform some work on property they own without a license, but electrical work beyond simple maintenance (like adding a 240-volt outlet) must be performed by a California-licensed electrician or the homeowner must hold an electrical contractor's license. In practice, many homeowners hire a solar installer to handle the electrical work (conduit, disconnect, breaker, inverter, grounding, conduit fill, NEC 690 compliance) and do the mounting rail installation themselves. The city will still require a licensed electrician to sign the electrical permit application. If you want to do ALL electrical work yourself, you must obtain a solar-specific electrical contractor's license or work under a licensed electrician's supervision (who assumes responsibility). Not recommended unless you have formal electrical training.
How long does PG&E's interconnection study take in Los Altos?
Typical timeline is 2–4 weeks from application submission to PG&E issuing a Feasibility Study Report. However, PG&E's current queue (as of 2024) is longer, and some interconnection studies are taking 6–8 weeks. The utility prioritizes smaller systems (under 5 kW) for faster review. You can track your application status on PG&E's online portal after submitting Form 79-1450. If your system is on a shared transformer or in a congested part of the grid, PG&E may require a more detailed Interconnection Agreement and cost-allocation study, which adds 4–6 weeks. Submitting a complete, accurate application (with a proper single-line diagram) reduces review time.
What is NEC 690.12 rapid-shutdown, and why does my plan need to show it?
NEC 690.12 (effective 2020) requires all grid-tied PV systems to be capable of rapid shutdown for firefighter safety. When a firefighter activates a roof-mounted shutdown switch (usually a label on the main disconnect or roof edge), the PV array must de-energize the DC circuit within 10 seconds. This prevents firefighters from being electrocuted while fighting a roof fire. Two compliance methods exist: (1) string inverters with built-in DC shutdown (array shuts down when AC breaker is opened), (2) micro-inverters (each panel has its own inverter and shuts down independently when AC breaker opens). Roof-mounted string inverter systems also require a combiner box with a DC disconnect that the shutdown switch controls. Los Altos inspectors will check that your plan shows the shutdown method clearly on the one-line diagram and that the hardware is listed and labeled per UL 4703. Missing or unclear rapid-shutdown documentation is the #1 reason for electrical permit rejections in Los Altos.
Do I need a roof structural engineer's report for a 5 kW system on my 1990s home?
Probably not. If the system load is under 4 lb/sq ft and your roof framing is standard wood (not damaged or sagging), Los Altos Building Official will accept the mounting manufacturer's design sheet and load calculations in lieu of a full PE-stamped structural report. However, you must provide: (1) manufacturer's specification sheet for the racking system showing it is approved for Seismic Design Category D and 90+ mph wind, (2) a site-specific fastening schedule (fastener spacing, diameter, type), (3) proof that the roof decking can accept the fastener pull-out loads (typical 2x lumber over 16 inches on-center is acceptable). If your roof is tile, metal, or if visual inspection reveals rot, water damage, or inadequate ventilation, the inspector may ask for an engineer's report. Call Los Altos Building Department and describe your roof type; they will tell you upfront whether an engineer is required.
What's the difference between a building permit and an electrical permit for solar?
Building Permit covers the structural/roofing work: mounting rails, flashing, fasteners, roof inspection, and verification that the roof can handle the load per IBC 1510. Electrical Permit covers everything that generates, distributes, or controls electrical power: PV panels (if roof-integrated), inverter, DC and AC conduit, disconnects, breakers, grounding electrode, surge arrestor, main panel modifications, and utility interconnection. Los Altos requires separate applications and separate inspections (roofing inspection, then electrical rough, then electrical final). Both must be finalized and passed before PG&E will activate net metering. Two permits also means two permit fees, but they can be applied for on the same day.
What happens if the city's plan review finds problems with my electrical diagram?
The Electrical Inspector will issue a Request for Information (RFI) listing specific items: missing conduit sizing, unclear breaker coordination, missing grounding details, rapid-shutdown labeling unclear, etc. You (or your installer) will have 10–15 days to resubmit a revised plan addressing each RFI item. The revised plan goes back into the review queue (another 5 days). If revisions are minor (e.g., adding a label or clarifying a circuit), the Inspector may approve over the phone and allow you to pay the permit and proceed to inspection. If revisions are major (e.g., the proposed breaker size is wrong for the inverter), you may need to re-design and resubmit, extending the process another 1–2 weeks. Submitting a complete, accurate plan the first time (with a licensed electrician's signature) avoids most RFIs.
Can I claim this as owner-builder work and avoid some fees?
No. Owner-builder status (per B&P Code Section 7044) allows you to avoid some licensing requirements, but Los Altos Building Department will still charge the full permit fee for both building and electrical work. You cannot get a fee reduction for owner-builder status in California. Additionally, the electrical portion of the work typically cannot be claimed as owner-builder without a licensed electrician's involvement (the electrician must pull the permit and take responsibility for NEC compliance). Your best approach: hire a licensed solar contractor to handle permits and electrical work, hire a roofer to handle flashing and roof fastening, and do the mounting rail bolting yourself if you are capable and want to save labor cost. This approach is not owner-builder in the legal sense, but it may save you $1,000–$2,000 in labor.
Do I need Fire Marshal approval if I add a battery to my system later?
Yes, potentially. If you install a battery system (e.g., Tesla Powerwall, Generac PWRcell) with capacity over 20 kWh, Los Altos Fire Marshal's office will likely require a separate Energy Storage System (ESS) permit and fire-safety review. For systems under 20 kWh (single Powerwall = 13.5 kWh), the Fire Marshal's requirement is less clear — some jurisdictions waive review, others do not. If the battery is installed inside the house (garage, closet), the Fire Marshal will require clearance to combustible materials, ventilation, and access per NFPA 855. If it is installed outside (pad-mounted), it requires a setback from property lines and a disconnect switch accessible to firefighters. Contact Los Altos Fire and Life Safety Division before purchasing a battery system; they will tell you whether a permit is required and what the review timeline is (typically 1–2 weeks).
If I submit my interconnection application to PG&E, do I still have to wait for PG&E approval before the city will issue a permit?
Not always. Los Altos Building Department will issue the electrical permit once your plan is complete and approved, even if PG&E's feasibility study is not yet finished. However, many inspectors require you to submit proof (via email from PG&E or application tracking number) that the interconnection application is in the system. Some departments make the final electrical permit (as opposed to the initial permit issuance) conditional on PG&E approval. Best practice: file the PG&E application immediately after you file the city permits, and include the PG&E application receipt number in your city permit packet. This demonstrates good faith and usually satisfies the inspector. You cannot legally operate (feed power to the grid) until PG&E approves and installs the bi-directional meter, but the city permit can be issued before that final approval.
What is the cost breakdown for a typical 5 kW solar system in Los Altos (permits only)?
Building Permit: $175–$300 (based on a ~$12,000–$15,000 project valuation at 1.5% of cost). Electrical Permit: $200–$350. Total city permits: $375–$650. PG&E interconnection application: No fee (utility function). If a structural engineer report is required: $1,000–$2,000 (not a city fee, but a third-party engineering cost). Total out-of-pocket for permits and engineering: $375–$2,650, depending on complexity. Most 5 kW systems on standard residential roofs do not require a structural engineer, so expect $375–$650. Note that this is permits only — it does not include the hardware, labor, roof flashing, electrician labor, or PG&E meter upgrade cost (which is at the utility's expense).