From signed contract to switch-on: the solar installation process, stage by stage

The nine stages at a glance

Three of the nine stages need a decision or a document from you. The rest belong to your installer, your local permitting office, and your utility, in that rotation. Your job across all nine is narrower than it feels: approve the final design before it becomes permit drawings, keep every document listed below, and know which stage your project is in at any moment. A project you can place on this table is a project under control, whatever its speed.

Two approvals run through the whole sequence and they belong to different authorities. Your city or county permits the physical work: the structure, the wiring, the roof attachments. Your utility approves the electrical relationship: a generator connected to its grid, exporting under the tariff your state page records. Neither approval substitutes for the other, and a system can hold one and still be blocked by the other.

Stage 1: the site survey checks what the sales visit estimated

A proposal is usually built from satellite imagery, your bills, and a sales visit. The site survey replaces those estimates with measurements. A surveyor or technician gets on the roof to measure the planes the array will occupy, checks the roof surface and structure, looks for shade the imagery may have missed or overstated, and opens your electrical panel to record its busbar and main breaker ratings and capacity and condition. Attic access, where the house allows it, lets the crew see the rafters the mounts will lag into.

Treat the survey as the last cheap moment to find problems, and as the point where adders can raise the price. A roof section with too little life left, a panel that cannot carry the added circuits without an upgrade, a vent or a shadow that removes four panels from the layout: each of these is a conversation at survey stage and a dispute at installation stage. The roof pages on this site work through the sequencing question by material, and the survey is where that question stops being general and becomes your roof, with a written answer.

Stage 2: the final design is the system you are actually buying

After the survey, engineering turns the proposal into a final design: the exact panel count and layout, the inverter, the mounting plan, and a production estimate rerun on the measured roof rather than the imagined one. Read this design the way the production estimate guide on this site teaches: size, tilt, azimuth, shade, and losses, all on paper. If the size changed since the proposal, the price test changes with it. The worked example below runs that arithmetic on a system that shrank at survey stage.

Approve the final design in writing, and treat anything that changes after your approval as a change order with its own signature and its own price line; the guide to solar price changes after the survey shows which adders are fair. One clause of the contract deserves a second look at this stage: the cancellation term. The Solar Energy Industries Association's Consumer Protection Principles note that federal and state law mandate a cooling-off period for home solicitations, and call for at least 5 business days after contracts are signed, during which customers must be able to cancel without penalty; the same principles ask installers for a short standardized disclosure of key terms such as contract length, payment schedule and financing terms. If you signed recently and the survey has already changed the system on offer, check where you stand inside that window before you approve the redesign.

One 8 kW project from signature to switch-on

Hypothetical example, with every figure stated. Suppose you sign for an 8.0 kW system at a gross price of $23,600. That is $23,600 divided by 8,000 watts, or $2.95 per watt, exactly this site's comparison line (the U.S. Department of Energy's Q1 2025 residential benchmark, $2.95 per watt DC, modeled market price for an 8 kW system, 2024 dollars, checked October 30, 2026). The survey then finds the layout only fits 7.2 kW once a vent and a shaded corner are measured on the roof itself. At the same price per watt, the revised total should be 7,200 watts times $2.95, which is $21,240. If the total stays at $23,600 for the smaller system, the price per watt has quietly risen to $23,600 divided by 7,200, or about $3.28 per watt, and the production estimate should have been rerun at 7.2 kW in the same revision. The system got smaller. Whether the deal got worse is a question only the per-watt figure can answer, which is why stage 2 of this process ends with that division, in writing.

Stage 3: permits, issued by people who do not work for your installer

With a final design, the installer files for the local building and electrical permits; in California and Colorado, state law caps what the city or county may charge for them, and the solar permit cost guide works the caps for an 8 kW system. The permitting office reviews the structural and electrical plans against local code, and it can send the plans back with corrections that the installer must answer before a permit issues. If your home sits under a homeowners association, its approval is a separate track again, owned by neither the city nor the installer, and it belongs on your own checklist rather than assumed into theirs.

Your part in this stage is one question, asked early: what is the permit number? A filed application produces a reference you can check with the permitting office directly, and an issued permit produces a document that should reach your file. A project described for weeks as being in permitting, with no number anyone will quote, is a project you cannot verify. Ask, and note the answer with its date. Before the permit stage, confirm that the company named on the contract holds the license the state requires; the license guide reads California, Texas, Florida and North Carolina.

How long the permit step takes: what 2025 permit records show

Stage 3 is the one stage with a national measurement behind it. Lawrence Berkeley National Laboratory's U.S. Distributed Solar and Storage 2026 Data Update (August 2026) times it from roughly 2.1 million solar permit records through 2025, drawn from building-permit data the lab buys from BuildZoom. The metric is apply-to-issue: the days between the date a permit application was filed and the date the permit was issued. It is the part of stage 3 you can check yourself, because both dates sit in the permit office's record under the permit number.

The shape of the data is more useful than any single average. The lab reports that zero-day durations, a permit issued the same day it was applied for, have been common over time, especially for residential and small non-residential systems. The slow tail is where homeowners get stuck, and the lab reports it at the 80th percentile: for residential PV-only systems that figure rose from 9 days in 2000 to 25 days in 2025. Read the other way, four in five residential PV-only permits in the 2025 records issued within 25 days of the application. Systems with a battery moved the opposite direction recently: their 80th percentile fell from 35 days in 2023 to 21 days in 2025. Comparing 2025 with 2024, the lab describes timelines as generally similar, but varying widely across individual projects.

Use the 25-day figure as a prompt to ask, not as a promise. If your permit has not issued 25 days after the application date your installer gave you, the project is slower than four in five residential PV-only permits in the 2025 national record, and that is the moment to ask for the office's correction letter, or for the date the revised plans went back in. The national number cannot tell you about your own permit office. The lab charts state-level medians separately, and the spread is real: in New York's 2025 records the PV-only timeline was zero days across the full percentile range shown, and comparing systems with and without a battery, the paired systems had shorter median timelines in some states and longer in others, roughly a 50/50 split.

Two limits keep the figure honest. Apply-to-issue starts when the application is filed, not when you signed, so the days your installer takes to finish the design and file are not in it. And it stops at issue, before installation, inspection and permission to operate, which are stages 5 to 7 on this page. The lab also tracks a second measure, apply-to-approve, which runs from the application to the permit's approval after inspection, and publishes it through the same online data viewer for anyone who wants the longer clock. It dropped records showing more than a year between application and issue as likely data entry errors, so the true slow tail may be a little longer than the published one.

Instant permits: what changes when your town uses SolarAPP+

Some permit offices have taken stage 3 almost out of the calendar. SolarAPP+ is an online permitting platform for residential solar and storage, developed by the government with the solar industry and managed by the SolarAPP Foundation, a non-profit; the foundation says that is why there is no cost to local governments to implement it. The platform runs automated checks on each data point of the system design against the most recent building, electrical, fire and structural codes and standards, and a code-compliant application receives its permit instantly. It also issues an inspection checklist with the permit, which the foundation says leads to fewer failed inspections at stage 6.

Its own counters showed more than 350 jurisdictions served and more than 150,000 permits issued when this page was checked on October 28, 2026. The foundation's site has a where-available section, so you can check your own address before you sign rather than after. The platform is available to licensed contractors, so if your jurisdiction is on the list, ask the installer whether it uses SolarAPP+ there and whether your design is one the automated review accepts; a standard rooftop system is the case it is built for.

An instant permit changes stage 3 and nothing else. The interconnection application at stage 4 still runs on the utility's timetable, the inspection at stage 6 still needs a visit, and permission to operate is still the utility's decision. A project with a same-day permit and a slow utility is still a slow project, so keep asking the stage-by-stage questions below even when the permit arrives the day it is filed.

Stage 4: the interconnection application runs on a separate track

In parallel with permitting, the installer applies to your utility for interconnection: permission to connect a generating system to the grid at your address. The application carries the final design, and the utility reviews it against its own requirements, which can include the meter at your house. The terms you interconnect under, how your exported energy is credited, are the export rules recorded on your state page, and the interconnection paperwork is where those rules stop being a summary and become your tariff.

Separate two utility decisions that are easy to blur. Approval of the application lets the project proceed toward installation. Permission to operate, stage 7, is a later and distinct decision, and it is the one that lets you switch the system on. An installer who says the utility has approved the project may mean either one. Ask which.

Stage 5: installation, the short visible stage

Installation is the stage the neighbours notice. The crew mounts the racking to the roof, sets the panels, installs the inverter and the required disconnects and labels, and runs the wiring between them and your panel. The electrical tie-in can involve a planned shutoff window at your house, which the crew should schedule with you rather than surprise you with. Clear access to the roof, the attic hatch if the crew needs it, and the electrical panel before the crew arrives, and keep pets and cars out of the work area.

At the end of installation the system is complete and, in the normal sequence, still off. It has not been inspected and the utility has not yet granted permission to operate. A finished-looking array producing nothing is not a broken array at this point. It is a project at stage 5 of 9, waiting on the two approvals that make it legal to run.

Stage 6: inspection, the pass everything waits on

The local inspector compares the installed work against the permitted plans and the applicable code: attachments, wiring, disconnects, labelling, and the rest of what the permit drawings promised. A pass produces the signed inspection approval for your file. A fail produces a correction list, the installer fixes the listed items, and the work is reinspected. A failed inspection is a normal branch of this process, not a catastrophe, but it does move every later stage, and you are entitled to the correction list in writing.

Now read your contract's payment schedule against this stage. Contracts tie the final payment to different milestones, and the distance between installation complete and permission to operate is exactly where that wording earns its keep. A final milestone defined by inspection approval or by permission to operate keeps your last payment aligned with a system that can legally run. One defined by installation day does not.

Stage 7: permission to operate, the utility's yes

With the inspection signed off, the utility completes its side: it reviews the inspection result, confirms the metering arrangement, swaps or configures the meter if its requirements call for it, and issues permission to operate. Only now should the system be switched on and left on. One utility's published process shows the order plainly: the Bureau of Indian Affairs' San Carlos Irrigation Project, a federally run utility in Arizona, issues its permission to operate letter and installs a new meter after the final inspection passes, and tells customers, for their safety, not to operate the system before receiving it. Your own interconnection agreement covers the system as an operating generator, and running it before the notice arrives can put you outside the arrangement you signed, whatever the weather is doing.

Keep the permission to operate notice with the inspection approval. Together they are the proof, years from now, that the system on your roof was approved as built. If the design is ever changed in a material way, added panels, a different inverter arrangement, these are the documents the new approval will be measured against.

Stage 8: switch-on and monitoring, in your name

Switch-on itself is brief: the system is energised, the inverter starts converting, and the monitoring platform begins recording production. The part of this stage with a long tail is ownership of the monitoring account. It should be registered to you, at your email address, with a login you have tested, not left under the installer's account with a password on a business card. Monitoring is how you will read this system for the rest of its life, and it is the record an inverter warranty claim or a production dispute will be argued from.

In the first weeks, read the monitoring the way the production estimate guide teaches: compare the shape of what the system produces against the monthly pattern the estimate promised, allowing for the weather you actually had. A system producing in line with its estimate in its first season is a closed question. One producing far under it, on clear days, with no shade explanation, is a warranty conversation to have while the paperwork is still warm.

Stage 9: the first bill, and the file you keep

The first utility bill after switch-on closes the loop the sales proposal opened. It shows your consumption, your exported energy, and the credit the tariff applied to it, which is the export rule from your state page expressed in dollars on your own account. Read it against the proposal's first-year claims with the right expectations: one bill is one month, production and usage both move with season, and a single month proves little either way. A bill with no export credit at all, on a system the utility has approved, is worth a call, because it can mean the billing setup lagged the permission to operate.

Then file the project. Contract and any change orders, final design, permits, inspection approval, permission to operate, equipment and workmanship warranties as separate documents, monitoring login, and the installer's contact for warranty service. The inverter replacement guide on this site describes the second purchase many systems carry; the file you build here is what makes that purchase, a roof repair, or a home sale a paperwork exercise instead of an excavation.

Documents to collect at each stage

• Survey findings and every design change confirmed in writing before you approve the final design.
• Final design in your file: panel count and layout, inverter, and the production estimate rerun on the measured roof.
• Permit number recorded, and the issued permit in your file.
• Interconnection application confirmed, with your export tariff terms from the application paperwork.
• Inspection approval signed and filed before you treat the work as complete.
• Permission to operate notice received from the utility before the system is switched on and left on.
• Monitoring account registered in your name and your email, login tested by you.
• Warranties filed as separate documents: equipment, workmanship, and roof penetration coverage are different promises.

Where projects stall, and the question that unblocks each one

Stalls cluster at the handoffs, and each handoff has a specific question that separates a delay from a disappearance. Permit corrections: ask what the correction was and when the revised plans went back in. A design change after survey: ask for the revised price per watt in writing, not a revised total alone. Electrical work surfacing late, a panel upgrade the survey should have priced (the 120 percent busbar check shows whether it is needed): ask for it as its own line, separate from the solar price, so the cost per watt of the system stays readable. A utility question about your meter or service: ask for the application's status reference, the same move as the permit number. An inspection failure: ask for the correction list and the reinspection date.

The pattern under all five is the same. A stall with a named stage, a named owner, and a next action with a date is a delay, and solar projects collect delays the way roofs collect weather. A stall described only as in process, week after week, with no stage and no document, is a management problem, and it is fixed by putting the question in writing and keeping the answer. Email you can file beats a phone update you cannot.

• Permit stage: ask for the permit application number, then the issued permit.
• Interconnection stage: ask whether the utility has approved the application, granted permission to operate, or neither yet.
• Any design change: ask for the new size, the new total, and the new price per watt, all three in writing.
• Any stall: ask for the stage, the person or office holding it, and the next action with its date.
• Every stage: take the document the stage produces and put it in the project file the same week.