The Solar Installation Process in California, Step by Step
Short version: going solar in California runs through seven stages — consultation and site survey, system design, contract, permit, installation day, city inspection, and finally your utility’s Permission to Operate (PTO). The install itself takes just a few days; the permit and utility steps drive most of the calendar. Here’s each stage, with an illustrative time range.
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- Going solar in California is a 7-stage process — consultation, design, contract, permit, install, inspection, and utility Permission to Operate (PTO).
- Installation day is often the fastest part (roughly 1–3 days). The permit and utility steps usually take the longest, and their timing depends on your AHJ and utility backlog.
- A passed city inspection is not the finish line — you can only legally switch the system on after the utility grants PTO.
- Cali Energy handles design, roofing, and electrical in-house, so the same team owns your project from the first site visit through PTO.
The full journey, from first call to switch-on
Most homeowners picture solar as “the crew shows up and mounts panels.” That day matters, but it’s one stage out of seven. Below is the whole path in plain English, with an illustrative time range for each stage. Treat the timings as ballparks — real duration depends on your Authority Having Jurisdiction (AHJ), your utility’s current queue, and whether your roof or electrical panel needs work.
| Stage | What happens | Who’s involved | Typical time* |
|---|---|---|---|
| 1. Consultation & site survey | Review your bills and goals; a technician measures the roof, checks shading, the electrical panel, and the roof condition. | You + solar consultant / surveyor | ~1–2 weeks to schedule & complete |
| 2. System design & proposal | Engineers size the array, lay out panels, pick the inverter/battery, and produce a written proposal and production estimate. | In-house design team | ~2–7 days |
| 3. Contract & financing | You sign, choose cash/loan/lease, and your 3-business-day right to cancel begins. | You + provider | Your decision + a 3-day cancel window |
| 4. Permit application (AHJ) | Plans submitted to your city/county building dept. In LA that’s LADBS. Small residential jobs may use an express or automated route. | Permit team + AHJ | ~a few days–several weeks |
| 5. Installation day | Roof mounting, panel racking, wiring, inverter, and any battery or main-panel upgrade. Usually the quickest stage. | Roof + electrical crews | ~1–3 days on site |
| 6. City inspection | An AHJ inspector verifies the install matches the approved plans and code before sign-off. | AHJ inspector | ~1–2 weeks to schedule |
| 7. Interconnection & PTO | Utility reviews the final package, may swap the meter, then issues Permission to Operate — the legal OK to turn it on. | Your utility (SCE/LADWP/etc.) | ~4–12 weeks |
*Illustrative ranges only — actual timing varies by AHJ and utility backlog. Sources: SCE Solar Billing Plan FAQ · LADWP Net Energy Metering · CPUC Solar Consumer Protection Guide.
Stage 1 — Consultation & site survey
Everything starts with your electricity use. We look at 12 months of bills to see how much you actually consume, then a technician visits to measure the roof, check its age and condition, note shading from trees or chimneys, and open your electrical panel to read the main breaker and busbar rating.
Two things often surface here. First, an aging roof — it’s far cheaper to replace a roof before solar than to remove and reinstall panels later. Second, an undersized electrical panel, which may trigger a main-panel upgrade. Because Cali Energy runs its own roofing and electrical crews, both get assessed on the same visit instead of being bounced to a subcontractor weeks later.
Stage 2 — System design & proposal
Our in-house design team turns the survey into an engineered layout: how many panels, where they sit, the inverter type, and whether a battery makes sense for your utility and goals. You get a written proposal with a production estimate and a clear price.
Battery sizing depends heavily on which utility you have. SCE, PG&E, and SDG&E customers are on NEM 3.0 (the Net Billing Tariff), where exported energy earns a time-varying credit that’s usually well below retail — so a battery to store your own daytime power is often worth modeling. LADWP is a municipal utility with its own more retail-like net metering and is not on NEM 3.0. If you’re unsure which rules apply to you, our NEM 3.0 explainer breaks it down.
Stage 3 — Contract & financing
Once you’re happy with the design, you sign and pick how to pay: cash, a solar loan, or a lease/PPA. Keep in mind the 2026 tax landscape — the 30% federal Residential Clean Energy Credit ended December 31, 2025 for owner-bought (cash/loan) systems, so 2026 cash and loan buyers get no federal credit. With a lease or PPA a third party owns the system and may claim a separate business credit, but you don’t claim it directly.
You have time to change your mind
California gives you generally at least 3 business days to cancel a residential solar contract for any reason — and 5 business days if you’re 65 or older. Exact terms can vary depending on where and how you signed, so read your contract. See the CPUC California Solar Consumer Protection Guide for the official version.
Stage 4 — Permit application (your AHJ)
Before anyone climbs on the roof, the design goes to your local building department — your Authority Having Jurisdiction. Every city and county runs its own process, so this stage is one of the most variable. Many small residential systems may qualify for an express or automated online permit pathway; larger or more complex jobs get a full plan review.
In the City of Los Angeles the AHJ is LADBS (Los Angeles Department of Building and Safety). Permitting has enough moving parts — fees, structural and electrical plan sets, instant-permit eligibility — that we cover it in its own deep-dive rather than cram it here. If you’re in LA, read Solar Permits in Los Angeles: the LADBS process.
Stage 5 — Installation day
This is the part people picture, and it’s usually the fastest: a typical residential system goes up in about 1 to 3 days on site. The work runs in a sequence:
Roof mounting
Crews locate rafters, flash and seal each mount, and attach the racking rails the panels clamp onto — the step that keeps your roof watertight.
Panels & wiring
Modules are set on the rails and wired together, with conduit run down to the inverter location.
Electrical tie-in
The inverter and any battery are connected, and the system is tied into your main service panel with proper disconnects and labeling.
Panel upgrade (if needed)
If the survey flagged an undersized or overloaded panel, the electrical crew handles the main-panel upgrade as part of the same job.
Whether a panel upgrade is required is not a blanket rule. It depends on the applicable NEC edition, your AHJ and utility, and your equipment configuration — a solar or exporting battery is a backfeed source (the 120% busbar rule), while an EV charger is a load (a service/load calculation). A listed smart panel can sometimes help manage loads but doesn’t automatically remove busbar limits; final approval always comes down to code review.
Stage 6 — City inspection
After the install, your AHJ sends an inspector to confirm the finished system matches the approved plans and meets code. If everything lines up, they sign off. If they flag something, we correct it and reschedule. Getting an inspector out typically takes about 1–2 weeks, depending on the department’s workload.
Stage 7 — Utility interconnection & Permission to Operate
Here’s the step homeowners underestimate most: a passed city inspection does not let you turn the system on. Your utility still has to review the final interconnection package, sometimes swap your meter for a bi-directional one, and formally issue Permission to Operate (PTO) — the legal green light to energize.
Timing here is the hardest to predict because it depends on the utility’s queue:
SCE: the utility says it targets processing standard interconnection packages within about 10 business days, but installPTO timing varies widely by utility, how complete the application is, the equipment, any corrections, and current backlog. As a rough guide from our recent project experience (not a utility guarantee), straightforward solar-only systems may clear in a few weeks while projects with a battery, a service upgrade, or corrections take longer. Once PTO is granted, SCE enrolls the account in the Solar Billing Plan.
LADWP: for small residential systems (under 10 kW), PTO may land within weeks of permit approval, though some customers report longer waits (ranges here are from our recent experience, not a utility guarantee) — LADWP itself notes this final step is the hardest to predict.
All of these are illustrative ranges pulled from utility guidance and installer reports, not guarantees. Once PTO arrives, we help you flip it on — that’s the day your system legally starts producing.
So how long does the whole thing take?
Add it up and, in the Los Angeles area, a straightforward residential project commonly runs about 8–14 weeks from signed contract to switch-on — based on recent Cali Energy residential projects, not a utility or permitting guarantee. The install itself is a few days; the calendar is dominated by the permit and utility stages, which are outside any installer’s direct control. A roof replacement, a main-panel upgrade, or a battery adds time. See real finished systems on our projects page.
One team from survey to PTO
When design, roofing, and electrical live under one roof, there’s no finger-pointing between a “solar company” and its subcontractors when the roof needs flashing or the panel needs an upgrade. Cali Energy (CSLB #1032379) does all three in-house, which keeps the hand-offs — the usual source of delays — inside one accountable crew. Questions on your timeline? Call +1-323-844-7777.
Frequently asked
How long does the whole solar installation process take in California?
In the Los Angeles area, a straightforward residential project commonly runs about 8–14 weeks from signed contract to switch-on — based on recent Cali Energy residential projects, not a utility or permitting guarantee. The physical install is only ~1–3 days; most of the calendar goes to the permit and utility (PTO) stages, which depend on your AHJ and utility backlog. Roof work, a main-panel upgrade, or a battery can add time.
What is Permission to Operate (PTO) and why does it matter?
PTO is your utility’s formal authorization to energize your solar system. A passed city inspection is not the finish line — interconnection and PTO are a separate utility process. The system should not be placed into normal parallel operation with the grid before utility authorization (PTO); limited commissioning or inspection testing may be permitted under the approved process. PTO timing varies widely by utility, application completeness, equipment, corrections and backlog. A straightforward project may clear in a few weeks, while projects with storage, a service upgrade or corrections can take longer. Any week ranges are from our recent project experience, not a utility service-level guarantee.
Can I turn on my solar panels right after the installation?
No. After installation you still need the AHJ inspection and then your utility’s Permission to Operate. Do not place the system into normal grid-parallel operation before PTO; limited testing or commissioning may be allowed under the approved inspection and utility process. Energizing it for normal use before PTO can create billing and safety problems. Once PTO lands, we help you energize it — that’s the true start date.
Do I need a new roof or electrical panel to go solar?
Sometimes. An aging roof is much cheaper to replace before panels go on. And an undersized service panel may need a main-panel upgrade — though whether one is required depends on the applicable NEC edition, your AHJ/utility, and your equipment. Both are checked during the site survey, and Cali Energy handles them in-house.
How does the permit step work in Los Angeles?
Your plans go to your local building department (the AHJ). In the City of LA that’s LADBS, and many small residential systems may qualify for an express or automated permit pathway. Because the details vary so much by jurisdiction, we cover them separately — see Solar permits in Los Angeles (LADBS).
Can I cancel after signing the solar contract?
Generally yes — California gives you at least 3 business days to cancel a residential solar contract for any reason, and 5 business days if you’re 65 or older. Exact terms can vary by where and how you signed, so check your contract and the CPUC Solar Consumer Protection Guide.
Related reading
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Get a free estimatePrepared by Cali Energy, July 2026. This article is for general educational purposes only and is not legal, tax, financial, engineering, or utility advice. Rates, incentives, codes, permit requirements, equipment specifications, prices, and program terms may change; figures and timelines are estimates, not guarantees. Confirm current requirements with the applicable utility, AHJ, program administrator, manufacturer, or a licensed professional. See our Content Disclaimer. Cali Energy · 19201 Parthenia St Unit E, Northridge, CA 91324 · CSLB #1032379 (B, C-10, C-39)