Site Survey Checklist: What a Good Pre-Install Visit Covers

A good solar site survey checks roof condition, structure, shade, electrical service, and homeowner goals before design. Skipping it leads to change orders and underperforming arrays.

A solar site survey is the field visit where installers verify that what was assumed in a desktop proposal matches the real building. Skipping steps here causes change orders, permit delays, and production shortfalls after install. A professional survey covers roof condition and structure, electrical service capacity, shading sources, equipment locations, access, and local code constraints. Homeowners and facility managers can use a structured checklist to evaluate whether an installer is thorough before signing a contract, and to prepare the property for a productive visit.

Roof documentation starts with material, age, pitch, and number of layers. The surveyor notes planes available for modules, dimensions, obstructions like vents and skylights, and chimney locations that trigger fire setbacks. They identify rafter or truss direction and spacing when possible, because attachment hardware must hit solid wood. Soft spots, prior leaks, curled shingles, or cracked tile flag pre-install roofing work. For flat commercial roofs, membrane type, insulation depth, parapet height, and drainage paths are recorded. Photos from multiple angles with reference objects help designers lay out rows without a second trip.

Structural and load questions connect roof data to engineering. Total array weight including racking and ballast must fit the deck rating. Snow load regions need winter coverage assumptions. Wind exposure category and building height influence attachment spacing. If the surveyor cannot confirm framing from the attic or drawings, they should schedule follow-up rather than guess lag spacing. Commercial sites may require core samples or pull tests on membrane attachments. Any planned re-roof within the array lifetime should surface during survey so penetrations are coordinated.

Electrical survey items focus on the main service panel, bus rating, available breaker spaces, and existing busbar configuration. The inspector records service voltage, utility meter location, and distance from array disconnect to panel. They note whether a main panel upgrade, subpanel, or derate is likely for the target system size. Grounding electrode condition, existing surge protection, and any generator or battery interconnection already present matter for design. For three-phase commercial services, phasing and demand charge context affect inverter selection. Photos of panel labels and interior wiring help engineers size conductors without opening every cover on install day.

Shading analysis on site complements satellite tools. Surveyors walk the property at different times if needed, identifying trees, neighboring structures, HVAC equipment, and antenna shadows. They mark keep-out zones on roof sketches. Even partial shade on one string can disproportionately hurt production on central inverter systems unless optimizers or microinverters are specified. Horizon elevation toward east and west matters on winter mornings and evenings. Documenting future tree growth or planned construction protects both parties from unrealistic production models.

Equipment placement and pathways round out the visit. Inverter or combiner location should be near the point of interconnection with cool, accessible wall space and clearance for service. Conduit routes from roof to equipment are traced to minimize exposure and respect finished spaces. Attic crawl paths, soffit penetrations, and interior wall finishes affect labor. Battery locations need ventilation, temperature limits, and code clearances. Rapid shutdown device placement relative to array edge is noted for NEC compliance. Commercial surveys add switchgear room access, transformer ratings, and tie-in points for monitoring.

Access, safety, and logistics prevent install-day surprises. Driveway clearance for material staging, forklift reach on commercial roofs, and HOA crane restrictions belong in survey notes. Steep roofs may require permanent anchor points or extra crew hours. Pets, gate codes, and parking rules for multi-day jobs should be captured. Weather exposure of south-facing yards where materials might sit matters in rainy seasons. If the attic is unfinished, lighting and walk boards may be needed for wire pulls.

Documentation deliverables separate strong installers from rushed ones. Expect a labeled roof diagram, string layout concept, single-line electrical sketch, equipment location map, and photo album. Shading report or production model inputs should reference what was seen on site, not only remote imagery. A written list of assumptions and exclusions clarifies who handles trenching, drywall repair, or tree trimming. Permit jurisdiction requirements like fire setbacks and placard locations should appear before ordering modules.

How owners should use the checklist: ask for a copy of survey notes before permit submission, verify production estimates cite the surveyed layout, and confirm change-order rules if field conditions differ. If only a salesperson visited without measurements, insist on a technical survey. For commercial properties, involve facilities staff who know roof warranty terms and shutdown procedures. A one-hour thorough survey costs far less than removing modules to fix a missed electrical constraint or undersized busbar.

Common gaps include ignoring attic access for conduit, underestimating walk distance from roof edge to inverter, and assuming panel upgrade is trivial without reading the main breaker rating. Another miss is failing to photograph existing roof penetrations that could be reused. Surveys that rely entirely on drone photos without attic or panel inspection leave blind spots. Treat the checklist as quality insurance: the goal is a buildable, permit-ready design that produces the kWh promised on the contract.

Drone imagery supplements but does not replace hands-on survey data. Lidar and satellite tools misread tree species growth rates and temporary shade from construction scaffolding on neighboring lots. Surveyors should note utility transformer size on the pole or pad because upstream capacity occasionally caps export even when the home panel has room. For properties with wells, septic fields, or easements, ground mount options may be restricted more than roof area suggests. Recording GPS coordinates of proposed array corners helps permitting on large rural parcels where address geocoding is imprecise.

Historic districts and design review boards may restrict visible modules from street-facing roof planes even when those planes have the best solar access. Survey notes should flag visibility lines from public right-of-way early so designers can propose alternate planes or low-profile racking before permit submission. Commercial tenants need landlord consent letters documenting who owns the array and who holds insurance; missing landlord sign-off stops projects after survey is complete.

Survey teams should record Wi-Fi signal strength at the proposed inverter wall if monitoring uses wireless gateways; weak signal may require a mesh node or cellular upgrade before commissioning.