Solar Site Survey Checklist: What to Inspect Before You Design and Install

Every failed installation we have audited over 8 years traced back to the same root cause: something the site survey missed. A busbar rating nobody photographed. A rafter span nobody measured.

A tree the customer forgot to mention. The site survey is where an installation succeeds or fails — everything after it, from design to permitting to the final inspection, only executes what the survey documented.

A weak survey does not fail loudly. It fails 3 weeks later as a change order, a redesign, a failed inspection, or a production number the system never hits. Each of those costs more than the survey itself.

A residential survey runs 30–90 minutes. The average change order it prevents runs $500–$3,000 in labor, materials, and schedule slip.

In this guide:

• The complete checklist across roof, shading, electrical, geometry, and logistics
• Exact measurements and photos to capture at each step, with pass/fail criteria
• How long surveys take for residential and commercial sites — and what drives the difference
• Remote vs. on-site surveys: what satellite and drone data can replace, and what it cannot
• How survey data flows into design, production modeling, and the proposal
• The 8 survey mistakes that cause the most expensive change orders

Why the Solar Site Survey Matters

The site survey is the only step in the solar sales process that touches physical reality. Everything else — the design, the production estimate, the proposal, the permit set — is a model. A model built on wrong inputs produces a wrong project, no matter how good the software is.

The economics are simple. A residential survey takes 30–90 minutes and costs 1 truck roll, roughly $150–$400 depending on drive time and market. A commercial survey takes 2–4 hours.

Compare that to the cost of what a missed item triggers: a panel upgrade nobody priced ($2,000–$4,000), a structural reinforcement discovered on install day, or a 20% production shortfall that voids the savings guarantee in your proposal. The survey is the cheapest insurance in the project. It is also the only one you fully control.

Across 400+ installations, we have found that most change orders trace back to 3 missed survey items. The first is the electrical panel busbar rating — photographed wrongly or not at all. The second is rafter spacing and condition in the attic.

The third is shading from vegetation the homeowner plans to trim “someday.” All 3 are 5-minute checks during the survey. All 3 are multi-thousand-dollar problems after contract signing.

The survey also sets customer expectations. A customer told at the survey stage that their 22-year-old roof needs work hears advice. A customer told after signing hears an upsell.

The same finding lands completely differently depending on when you surface it, and the survey is your only chance to surface it early.

Finally, the survey is a compliance document. Interconnection applications, structural letters, and permit sets all cite site conditions. If the survey record is thin, every downstream document inherits that weakness.

Our guide on how to organize a solar panel installation covers how survey findings feed the full project schedule.

Roof Condition and Structural Integrity Checklist

The roof decides whether the project happens at all. A solar array carries a 25–30 year service life, so the roof under it needs at least 10–15 years of remaining life to avoid a remove-and-reinstall job that costs $3,000–$8,000 on a typical residential system. This is the first thing to assess, before any measurement.

Start with the roof surface itself. Walk it where pitch and condition allow, and document what you see with dated photos. Then verify the structure from the attic — the surface tells you what the roof looks like, but the attic tells you what it can carry.

The attic inspection takes 10 minutes and answers 3 questions the roof surface cannot:

1. Rafter or truss size and spacing. Measure 1 rafter with a tape — 2×4, 2×6, or larger — and the on-center spacing, typically 16 or 24 inches. Record the span between bearing points.
2. Lumber condition. Look for water stains, mold, cracked members, and sistered repairs. Photograph anything abnormal with a tape in frame for scale.
3. Decking type and thickness. Plywood, OSB, or board sheathing, and approximate thickness. This determines pull-out values for attachments.

1 tradeoff to be direct about: declining a project because of roof condition feels like lost revenue, and some competitors will take the job anyway. In our experience, projects installed on roofs with under 10 years of life generate warranty disputes and remove-and-reinstall costs that erase the margin of 2 good projects. The honest survey is cheaper.

Shading and Solar Access Checklist

Shading determines production, and production determines whether the savings in your proposal are real. A 10% shading underestimate on a system sold with a production guarantee is a liability that compounds for 25 years. This section of the survey deserves the most time on the roof.

Solar access is the share of the sun’s path across the sky that reaches the array unobstructed. The critical window is 9 AM–3 PM solar time, when the sun delivers roughly 80% of the day’s energy. Document every object that intersects that window from the array’s position — not from the ground.

For measurement, you have 3 options. A physical shade instrument — a solar pathfinder or similar device — captures the horizon profile from the array corner and accounts for sun path by month. A drone with photogrammetry builds a 3D site model.

Software-based shade modeling from satellite and lidar data covers geometry without a site visit, and solar shadow analysis software can run hour-by-hour shade simulation on the 3D model before anyone climbs a ladder.

Follow this sequence on site:

1. Stand at each proposed array corner and photograph the horizon at eye level, facing the equator.
2. Record a panorama video panning east to west across the southern sky.
3. Measure tree heights with a clinometer or the shadow method, and log the distance from the array edge.
4. Note which trees the customer owns and which belong to neighbors — you can trim the first kind.
5. Ask directly: “Are you planning to remove or trim any trees?” Record the answer verbatim.

The first-hand lesson here: deciduous trees are the single most misjudged shade source. A leafless maple in a February survey looks harmless. In June, its canopy casts shade 1.5 times the crown width you measured.

Always model trees at full summer canopy, and always add a growth allowance of 1–2 feet per year for species under 40 years old.

Electrical Panel and Service Checklist

The electrical inspection determines how the system interconnects — and whether the project needs a service upgrade that changes the quote by thousands of dollars. This is where the most expensive survey misses happen, because the panel label is a 30-second photograph and the cost of skipping it is a $2,000–$4,000 upgrade discovered after contract.

Open the main panel deadfront only if you are qualified and equipped to do so. In many markets, photographing the exterior label, the main breaker rating, and the breaker layout with the deadfront closed is sufficient for the survey stage. Leave live diagnostics to the licensed electrician on the project.

2 panel brands deserve a hard rule: Federal Pacific Electric (Stab-Lok) and Zinsco panels have documented failure histories, and most insurers and authorities having jurisdiction require replacement before solar interconnection. Photograph the label, and quote the replacement in the original proposal — not as a change order.

The interconnection method depends on what you find. The 120% rule under NFPA 70 (National Electrical Code) Article 705.12 allows a solar breaker up to 20% of the busbar rating above the main breaker on a typical 200A panel.

When the math does not work, your options are a main breaker derate, a supply-side (line-side) tap, or a panel upgrade. Each has a different cost and permitting path, so the survey must capture the data to decide before the proposal — the surveyor does not decide on site.

Also check the utility meter location and the route between array and panel. A detached garage array with a 150-foot trench run to the main panel adds real cost. Measure the distance, note surface material along the route (lawn, driveway, concrete), and photograph the path.

Roof Geometry and Layout Measurements

Design software is precise, but it is only as precise as the dimensions you feed it. A 2-foot error in roof width can shift the layout by a full panel column, which changes string sizing, rail lengths, and the bill of materials. Measure to the inch on everything that touches the layout.

The 3 primary geometry values are azimuth, tilt, and dimensions:

1. Azimuth — the compass direction each roof plane faces, in degrees from true south. Use a compass app with magnetic declination correction, and measure each plane separately. A “south-facing” house often has planes at 165° and 195°, not 180°.
2. Tilt — the roof pitch in degrees, measured with an angle finder on a shingle or from the attic against a rafter. Record both the degree value and the rise-over-run (for example, 6:12 ≈ 26.6°).
3. Dimensions — eave length, ridge length, and rake length for every candidate plane. Cross-check: eave and ridge lengths should reconcile within a few inches.

Then map every obstruction on each plane with position and size:

Fire code pathways come next. Most US jurisdictions following the International Fire Code require clear pathways on residential roofs — typically 3-foot-wide access paths from eave to ridge and setbacks at the ridge for smoke ventilation. The exact requirement varies by authority having jurisdiction, so record which AHJ governs the site and verify its adopted code edition.

Reserve these pathways in the layout from the start, not after the plan reviewer rejects the set.

For flat commercial roofs, add membrane type and condition, parapet height, roof access point, and ballast or mechanical attachment feasibility. Also pull the building’s structural drawings if they exist — purlin spacing and deck gauge determine attachment spacing on metal buildings.

Safety, Access, and Logistics Checklist

A design can be perfect and still fail on install day because a ladder cannot reach the eave, the dog is aggressive, or the only staging area is the neighbor’s driveway. Logistics findings belong in the survey record, because they change crew size, equipment rental, and schedule.

For commercial sites, add crane swing radius and street permits, roof load limits for staged pallets, tenant coordination, and whether work must happen outside business hours. A 200 kW rooftop project can require 2 crane days, and discovering the need for a street closure permit the week before installation slips the schedule by a month.

1 habit that pays for itself: end every survey with a 5-minute customer walkthrough. Tell the customer what you found, what happens next, and what you need from them — gate access, attic cleared, pets secured. Customers who hear this at the survey stage generate far fewer day-of-install surprises than customers who get a reminder email.

Remote vs. On-Site Surveys: What Works When

The fully remote survey is the industry’s favorite promise right now, and it is half true. Satellite imagery, lidar, and drone photogrammetry genuinely cover roof geometry and shading for most residential sites. Services like Google Project Sunroof show how far imagery-based solar assessment has come.

But imagery cannot tell you the decking is soft, the panel is a Federal Pacific, or the rafters are 2×4 at 32-inch spacing.

Here is the contrarian position we hold after running both workflows: the survey model you choose matters less than knowing exactly which failure modes each model cannot catch. Companies that go fully remote to save $200 per survey often spend $1,500 per project absorbing the misses — they just never attribute the cost back to the survey decision.

The hybrid workflow is the one that scales. Run the remote pass first: pull imagery, build the 3D model, run the shade simulation, and pre-fill the survey form. Then send the surveyor on site with a targeted checklist — verify condition, open the attic, photograph the panel, confirm 2 or 3 critical dimensions.

This cuts on-site time from 90 minutes to 30–45 minutes on a standard residential job without giving up the checks imagery cannot do.

Where remote fails outright, send the truck: roofs under tree canopy where imagery cannot see the surface, tile and specialty roofs where attachment method depends on what is under the tile, homes built before 1990 where panel brands and wiring methods vary wildly, and any commercial flat roof where membrane condition and ballast feasibility drive the design.

Age of imagery is the silent failure. Satellite photos can be 1–3 years old in some regions. A new second story, a removed chimney, or a felled tree makes the remote model wrong in ways nobody notices until the crew arrives.

Always check the imagery date, and always have the surveyor reconcile the model against reality on any site you visit.

From Survey to Design: How Data Flows Into Your Proposal

The survey only creates value when its data reaches the design model intact. The failure mode we see most often is transcription: a surveyor writes “roof pitch 30°” on a form, a designer reads “30” and models a different plane, and the layout drifts. The fix is a workflow where survey data enters the design tool once, in structured form, and flows forward without re-typing.

The pipeline has 5 steps:

1. Capture. Structured survey form — digital, with required photo fields and numeric entries, not free text. Every measurement lands in a defined field with units.
2. Model. Build the 3D site model in solar design software from the survey dimensions, imagery, and photos. Discrepancies between model and survey photos get resolved now, not at permitting. Modern solar software imports drone and satellite data directly, which removes most manual tracing.
3. Simulate. Run hour-by-hour shading on the model and calculate production. The generation and financial tool turns the shade-adjusted production number into a savings projection using the customer’s actual utility rate.
4. Propose. The design, production estimate, and financials flow into the customer-facing document. Solar proposal software that reads the design model directly eliminates the copy-paste errors that plague manual proposals.
5. Verify. Before the proposal goes out, 1 person reconciles the proposal against the survey record — array size, panel count, production number, and any flagged work like a panel upgrade or re-roof.

This flow is exactly what the residential solar design workflow describes end to end. The point worth repeating: every number in the proposal should be traceable back to a survey field or a simulation output. If a number has no traceable source, it is a guess, and guesses become change orders.

Data quality rules that keep the pipeline clean:

• Photos over notes — a panel label photo survives; a handwritten “200A” gets misread.
• Units on every number — 26.6° tilt vs. 6:12 pitch are the same roof, but mixing formats causes rework.
• 1 record per site — survey, photos, and measurements live in the project file the designer opens, not in email threads.
• Surveyor sign-off on completeness — the form cannot close with required fields empty.

For solar installers running more than a few surveys a week, this integration is where the hours come back. The survey stops being a document someone re-reads and starts being the input the whole project runs on.

Common Site Survey Mistakes That Cause Change Orders

These 8 mistakes account for most of the change orders and redesigns we see across installers. Every one is preventable with 5 extra minutes on site.

1. Not photographing the panel label. The brand, model, busbar rating, and main breaker are all on that label. “200A panel” written on a form is not enough — the 120% rule math depends on the busbar, not the breaker.
2. Measuring only the main roof plane. Dormers, garage roofs, and additions change the layout options. Measure every plane that could hold panels, even the ones you do not plan to use.
3. Ignoring winter sun angles. A site clear at 2 PM in July can be shaded by the neighbor’s house from November through February. Model December 21, not just the survey date.
4. Trusting the customer on roof age. Customers routinely underestimate roof age by 5–10 years. Check permit records, shingle condition, and the seller disclosure if the home changed hands recently.
5. Skipping the attic. 10 minutes in the attic catches water damage, undersized rafters, and prior repairs. Skipping it is how “straightforward” installs become structural engineering projects.
6. No obstructions map. Vents and skylights that are not on the survey sketch end up where the design put panels. Every penetration gets a position, not just a count.
7. Forgetting the interconnection route. The array-to-panel path — trench, conduit run, attic path — adds real material and labor cost. Measure and photograph it during the survey.
8. Designing from the summary instead of the record. The survey summary says “good roof, south-facing, no shade.” The survey record says 15° east of south, 2 vent stacks, and a 40-foot maple at 25 feet. Design from the record.

The pattern across all 8: the survey was done, but the finding never reached the design. A checklist only works if it produces a complete record — and the record only works if the designer actually uses it. This is why we treat the survey form as a design input with required fields, not a report someone files.

Conclusion

A solar site survey is not a sales formality — it is the engineering input the entire project runs on. The 5 inspection areas are fixed: roof condition and structure, shading and solar access, electrical panel and service, geometry and measurements, and safety and logistics. Miss any one of them, and the miss surfaces later at 10 times the cost.

The checklist in this guide is built to be used, not read once. Print the tables, turn them into your survey form, and make the photo fields required. A form that can close with empty fields will close with empty fields — usually on the projects that needed them most.

Budget the time the checklist needs. 30–90 minutes for residential, 2–4 hours for commercial, and a remote pass before the truck roll whenever imagery can carry part of the load. Photograph everything, record measurements with units, and design from the survey record — never from memory or the summary line.

Treat every survey finding as a pricing input, too. Roof work, panel upgrades, trench runs, and crane days all belong in the original proposal. A survey that surfaces cost early is a sales tool, because customers trust the installer who tells them the full number first.

None of this requires new hires or new trucks. It requires a standard checklist, a structured form, and the discipline to fill every field on every site. The companies that do this consistently quote more accurately, install faster, and argue less.

The installers with the lowest change-order rates are not the ones with the best installers. They are the ones with the most disciplined surveys. Make the checklist standard, make the record complete, and let the design inherit clean data.

Your crews, your customers, and your margins will all show the difference.

Frequently Asked Questions

What is a solar site survey?

A solar site survey is an on-site inspection that documents roof condition, shading, electrical panel capacity, structural integrity, and local conditions. It determines whether a property is suitable for solar and informs the system design.

What should you check during a solar site survey?

Check roof age and material, orientation and tilt, shading from trees and structures, electrical panel capacity, available breaker space, roof structural condition, and access for installation equipment.

How long does a solar site survey take?

A residential solar site survey typically takes 30–90 minutes. Commercial surveys take 2–4 hours depending on roof complexity, building height, and the number of electrical panels to inspect.

Can a solar site survey be done remotely?

Remote surveys using satellite imagery, lidar, and drone photos can cover shading and roof geometry. But roof condition, electrical panel details, and structural issues still require an on-site visit in most cases.

What tools do you need for a solar site survey?

Basic tools include a tape measure, angle finder, compass or phone app, camera, electrical panel cover opener, flashlight, and safety equipment. Professional tools include a solar pathfinder, shade measurement device, or drone.

What happens after a solar site survey?

The survey data goes into system design. The designer sizes the array, models shading, selects equipment, and produces a proposal. The survey findings also inform permitting, structural engineering, and installation planning.