Table of Contents
A roof that measures 14 feet on paper and 12 in real life can sink a solar design. So can a main panel photographed from across the garage, or a vent stack nobody wrote down. A poor solar site survey doesn’t look like a problem on day one. It looks like a finished drawing. The trouble arrives three weeks later, when the permit office sends the plans back or the install crew finds the array doesn’t fit.
Short answer: A poor solar site survey causes design errors because every later document, from the panel layout to the single-line diagram to the structural letter, is built on survey data. Wrong dimensions, missing electrical details or unrecorded obstructions produce a design that fails plan review or can’t be installed as drawn. Each failure triggers a revision cycle, and revision cycles are where project delays come from.
What does a solar site survey actually need to capture?
A solar site survey needs to capture four things: the physical roof or ground area, the structure underneath it, the existing electrical service, and anything that shades or blocks the array. Miss any one of them and the designer is guessing.
Most surveys get the first item roughly right. The photos are there, the roof looks big enough, and the satellite image seems to agree. The other three are where things slip. Here’s what a complete record includes:
- Roof geometry: true dimensions of each plane, pitch, azimuth, and the location of ridges, hips, valleys and edges.
- Roof condition and covering: material, age, layers, and visible damage. A tired roof affects mounting choices and sometimes the whole decision to proceed.
- Structure: rafter or truss size, spacing and span, plus attic access photos that actually show the framing.
- Obstructions: vents, skylights, chimneys, satellite dishes, HVAC units, and plumbing stacks, each with a position and a size.
- Electrical service: main panel make, model and bus rating, main breaker size, available breaker spaces, meter location and the distance between meter, panel and the proposed inverter spot.
- Shading: trees, neighboring buildings, and rooflines that cast shadows, with measurements or tool readings instead of a note saying “some shade.”
- Access and safety: ladder access, fall protection concerns, setbacks from roof edges, and any local access pathway requirements.
If your team treats the solar site survey as a photo-taking exercise, the design team will spend its time chasing the missing numbers. That chase costs days, and a solar site survey built for speed often costs more than it saves.
How does a poor solar site survey cause design errors?
It causes design errors by feeding the designer inaccurate or incomplete inputs. The designer then makes reasonable decisions based on bad information, and the drawing looks correct even though it isn’t. The errors tend to cluster in three places.
Roof measurements and structure
Measurement errors are the most common. A tape reading taken at an angle, a satellite image with outdated roof geometry, or a pitch estimated by eye can each shift the usable area enough to change the module count. If the array was drawn with a few inches of margin and the roof turns out to be smaller, a whole row falls off the plan.
Structural gaps are quieter and more expensive. Without rafter size and spacing, an engineer can’t confirm the roof carries the added load, and the mounting points can’t be placed with confidence. The usual outcome is a stalled structural letter and a request for more photos. Sometimes it’s worse: the install crew opens the attic and finds framing that doesn’t match the assumptions.
Electrical service and main panel
Electrical errors are where a poor solar site survey does the most damage to schedules. A designer needs the busbar rating and main breaker size to check whether the backfeed from the solar system is allowed. In the US, the NEC rules on busbar loading, including the 120% allowance in NEC 705.12, drive many of these decisions. If the survey only shows a blurry panel door photo, the designer can’t verify anything.
The usual consequences look like this:
- A supply-side connection or a main panel upgrade becomes necessary after the permit is already submitted.
- The single-line diagram shows a breaker size that doesn’t match the real panel label.
- Conductor runs are drawn too short because nobody measured the distance from the inverter location to the service.
- The meter or disconnect position forces a different equipment layout than the one sold to the homeowner.
Shading and obstructions
A missing obstruction in the solar site survey is a design error you can see only after installation starts. A plumbing vent in the middle of a planned module row, a chimney with a larger clearance zone than assumed, or a tall tree on the south side that wasn’t flagged. Each one changes the layout or the production estimate.
The production estimate matters because it was probably already promised to the customer. If the sales proposal assumed a clear roof and the real roof loses 12% to shading, someone has to have an awkward conversation.
Why do survey gaps turn into permit rejections and project delays?
Survey gaps turn into delays because every gap becomes a correction loop. The reviewer, the engineer or the installer finds the problem, asks for information, and the project waits while someone goes back to the site or the customer. Those loops add up faster than most teams expect.
Plan reviewers at the authority having jurisdiction (AHJ) check whether the drawings are internally consistent and match code. They don’t visit your site. If the plan set shows a 200A panel and the photo attached shows a 150A label, the reviewer sends it back. The same thing happens in the UK when a DNO application under G98 or G99 doesn’t match the property’s actual supply details. The application gets queried, and the clock restarts.
This table shows how common survey gaps flow through to design problems and then to schedule impact:
| Survey gap | Design error it creates | Typical consequence |
| Roof dimensions estimated from satellite only | Array doesn’t fit the real roof plane | Layout redraw, new module count, updated proposal |
| No rafter size or spacing recorded | Structural assumptions can’t be verified | Engineering hold, extra site visit or attic photos |
| Panel label not photographed clearly | Wrong busbar or main breaker rating in the single-line diagram | Permit rejection or late panel upgrade |
| Roof obstructions missed | Modules placed over vents or inside clearance zones | Field changes on install day |
| Shading not measured | Production estimate overstated | Customer dispute, redesign, or lost sale |
| Service entrance and meter location unclear | Equipment placed where code or access rules don’t allow | Revised plans and resubmission |
None of these are exotic. They’re ordinary mistakes. That’s the point: delays rarely come from one dramatic failure. They come from small, avoidable gaps that each cost a few days.
What’s different about a solar site survey for US and UK projects?
The core of a solar site survey is the same in both markets, but the compliance details differ. US surveys feed NEC-based plan sets reviewed by a local AHJ. UK surveys feed MCS-aligned designs, DNO notifications and wiring checks against BS 7671.
If you work across both, build the survey form so it covers each market’s needs without turning into a 40-page document.
| Survey item | US projects | UK projects |
| Review body | Local AHJ, sometimes plus the utility | DNO for grid connection; MCS certification for eligible systems |
| Electrical focus | Panel busbar and main breaker rating, rapid shutdown, interconnection method | Consumer unit details, earthing arrangement, supply type, cut-out and meter position |
| Grid application | Utility interconnection and permission to operate (PTO) | G98 for smaller systems, G99 for larger ones |
| Roof access and setbacks | Fire code pathways and setbacks that vary by jurisdiction | Edge zones, wind exposure and mounting standards |
| Shading assessment | Required by many proposals and utility incentive programs | Needed for MCS-style shading calculations |
Rules change, and they differ by council, county and network operator. Always check the current local requirement before you finalize a survey template. A form that was correct for one AHJ may leave out something the next one expects.
What does a bad solar site survey look like in a real project?
Here’s a typical scenario, built as an illustration rather than a specific client case. A residential installer sells a 9 kW system based on a satellite image. The survey technician visits for 30 minutes, takes eight photos, and records the roof pitch by eye.
The designer lays out 22 modules on the south-facing plane. The permit package goes out. Two weeks later, the AHJ returns it with a comment: the single-line diagram lists a 200A busbar, but nothing in the submission proves it. The installer sends a technician back to photograph the panel. It’s a 150A busbar.
Now the backfeed calculation fails. The options are a main panel upgrade, a line-side tap if the utility and local code allow it, or a smaller system. The customer has already signed for 22 modules. The designer redraws the layout, the engineer reissues the letter, and the permit gets resubmitted. Meanwhile the crew scheduled for next week is released to another job.
A solar site survey that took another 20 minutes, with a clear panel label photo and a recorded busbar rating, would have caught every bit of it before the sale closed.
How can you fix your solar site survey process?
You fix it by standardizing what gets collected, checking it before design starts, and making the solar site survey owner accountable for completeness. A checklist alone isn’t enough. It needs a gate: the design team doesn’t begin until the survey passes review.
- Use one survey template for every job. It should have required fields for dimensions, structure, electrical and shading, with no optional “notes” box standing in for real data.
- Require photo standards. Specify the angles and distances. A panel label shot needs to be readable at full zoom. Attic photos need to show rafter size and spacing with a tape in frame.
- Measure, then cross-check. Compare field measurements against satellite or drone data. If the two disagree by more than a small tolerance, resolve it before design.
- Review surveys before design starts. A short completeness check, ideally by someone other than the surveyor, catches missing items while the technician is still near the property or the customer is still engaged.
- Record electrical details as text, not only as photos. Photos can be blurry or cropped. A typed busbar rating, main breaker size and available spaces survive a bad image.
- Train surveyors on why the data matters. People collect better information when they know which drawing or calculation it feeds.
- Feed errors back. When a design is returned because of survey data, log it. After a few months you’ll see which fields fail most often and can fix the template.
This isn’t glamorous. But a team that tracks survey-related rework usually finds the problem is concentrated in two or three recurring misses, which makes it easy to fix.
Are remote surveys, drones and satellite imagery good enough?
Remote tools can speed up a solar site survey, but they rarely replace on-site verification for the electrical and structural details. Satellite and drone imagery are good for rough roof geometry, orientation and large shading sources. They can’t read a panel label, count breaker spaces or see rafter dimensions inside the attic.
A sensible approach is to use remote imagery for early sales proposals and preliminary layouts, then confirm everything that affects code compliance and structural safety with on-site data before final design. Treat the remote measurement as a first draft, not a final answer.
Some teams ask homeowners to submit photos themselves. That can work if you give clear instructions, ideally with a short guide showing exactly which photos you need. It fails when instructions are vague and nobody reviews what comes back.
How does One Place Solar support survey-to-permit accuracy?
One Place Solar is a solar design, engineering and permitting company based in Agra, India, serving installers and EPC contractors in the US, UK, Canada, Australia, New Zealand and the UAE. Our team works from survey data to produce permit plan sets, PE stamping, PTO and interconnection support, sales proposal design, and CAD quality checks.
That position gives us a clear view of how survey quality shows up downstream. When the field data is complete, plan sets move through review faster. When it isn’t, our designers flag the gaps early so your team can fix them before submission rather than after a rejection. A CAD quality check on the finished drawings also helps catch mismatches between the survey and the plan set.
Frequently asked questions
What is a solar site survey?
A solar site survey is an on-site or remote assessment that records the roof or ground area, structural details, electrical service and shading at a property. Designers use the results to create the panel layout, electrical drawings and permit documents. The more accurate the survey, the fewer revisions the project needs.
How does a bad solar site survey delay a project?
A bad solar site survey delays a project by creating errors in the design that reviewers or installers later discover. Each discovery triggers a correction loop, such as a return site visit, a redesign, a new engineering letter or a permit resubmission. Those loops can add days or weeks, depending on the reviewer and the scope of the fix.
What information is most often missing from solar site surveys?
The most commonly missing items are clear main panel details, including busbar rating and breaker spaces, rafter size and spacing, and measured obstruction locations. Shading data is also frequently vague. These gaps affect electrical compliance, structural review and production estimates.
Can you do a solar site survey remotely?
You can complete part of a solar site survey remotely using satellite or drone imagery, which helps with roof outline and orientation. Electrical and structural details usually still need on-site verification or detailed customer-supplied photos, because remote tools can’t read panel labels or see framing inside the attic.
Who should perform a solar site survey?
A trained surveyor, installer technician or designer familiar with the required data should perform it. Whoever does it needs to know what the design and permit teams need, not only how to take photos. A second person reviewing the finished survey before design begins reduces missed items.
How long should a solar site survey take?
It depends on the property and the system type. A straightforward residential roof with easy attic access takes less time than a complex multi-plane roof, a ground mount or a commercial building. A rushed visit is a common cause of missing data, so build in time for electrical and structural checks.
Next step
Review your current survey template against the checklist above, then pick the three fields that cause the most rework and make them mandatory. If you want a second pair of eyes on a plan set before it goes to the AHJ or DNO, contact One Place Solar and our design team can check it against your survey data.