Quick overview (why it matters)
A site survey collects the physical, electrical and environmental facts needed to size the system, plan the mounting and wiring, estimate energy yield, identify permitting constraints, and produce the bill of materials and cost estimate. Doing it well avoids rework, unexpected costs, and poor long-term performance. For solar resource numbers you’ll typically use modeled GHI (global horizontal irradiance) maps first, then verify shading and local conditions on site. (Global Solar Atlas, PVWatts Calculator)
Tools & documents to bring
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Tape measure, laser distance meter
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Digital camera or smartphone (take many geotagged photos)
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Inclinometer / smartphone app for tilt & azimuth (compass + clinometer)
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Solar shading tool (Solar Pathfinder or Solmetric SunEye) or smartphone shading app
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Multimeter, clamp meter, and basic electrical tester
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Ladder, harness & PPE for working at height (helmet, gloves, safety glasses)
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Building drawings / roof plan (if available)
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Site survey form / checklist (paper or tablet) — use a checklist template. (SepiSolar, SafetyCulture)
Pre-visit (desktop) checks — what to do before you go
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Energy use & customer brief — get the customer’s recent utility bills (12 months if possible) or a self-consumption profile.
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Preliminary resource check — run a quick solar resource lookup (Global Solar Atlas, PVWatts, or similar) to get average daily GHI for the site area and to produce a first-cut production estimate. Example: Dhaka GHI typically lies around 4.3–5.0 kWh/m²/day (use the precise point for final design). (Global Solar Atlas)
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Satellite imagery & roof outline — measure available roof or ground area from satellite images (Google Earth / mapping tools) to get approximate dimensions and obstructions.
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Permits & local codes — check local permitting requirements, building or heritage restrictions, and utility interconnection rules.
Why: the desktop pass identifies potential deal-breakers (very low irradiance, extreme shading, or permit issues) before you dispatch a crew.
On-site Step-by-Step Survey
1. Safety & access briefing
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Confirm safe access, document anchor points, note any fragile roof areas.
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Use fall protection as required. Do not work alone on roofs.
2. Document site identity & orientation
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Record address, GPS coordinates, and take wide-angle photos: roof faces, ridge lines, nearby trees, chimneys, vents, electrical meter, main distribution board (MDB), and point of interconnection. Photograph from multiple angles and at different times if possible.
3. Measure usable mounting area
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Measure each roof plane (length × width) and usable clear space (exclude obstructions, setback margins, gutters).
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Note roof material (tile, metal, concrete), roof age, signs of leaks, and structural condition—get roof warranty/age from owner.
4. Measure tilt & azimuth
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Use a clinometer or smartphone app to measure the roof pitch (degrees) and compass heading (azimuth). Record each plane separately. Typical optimal tilt ≈ latitude for yearly maximized yield; adjust for local seasonal goals.
5. Shading analysis (critical)
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Perform a full shading assessment for each intended array plane:
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Use a SunEye / Solar Pathfinder to record horizon profile and shade objects (trees, chimneys, adjacent buildings).
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Take photos at solar noon and note seasonal shading (winter vs summer).
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Record any near-field shading that will impact morning/afternoon production — partial shading can dramatically reduce string yields unless microinverters/optimizers are used. Use shading data later in PVsyst/HelioScope for accurate loss modeling. (SepiSolar)
6. Structural & mounting check
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Inspect rafters/trusses layout from attic or via structural drawings. Measure rafter spacing, covering thicknesses, and available attachment points. Confirm roof can carry additional dead + live loads (panels + mounting + wind/snow loads) or note need for structural engineering sign-off.
7. Electrical infrastructure & routing
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Locate meter, main breaker, distribution board, and meter socket type. Document main service rating (e.g., 100 A, 200 A) and free spaces in the panel.
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Decide inverter and battery locations (ventilation, distancing, access). Measure cable routes and distances to minimize voltage drop. Photograph all electrical rooms and take panel serials and labels.
8. Site constraints & permits
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Note setback rules, fire service clearances, HOA or utility restrictions, and disconnect access points required by code.
9. Environmental & logistical notes
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Recording roof slope direction relative to prevailing winds, potential for salt/industrial fouling, typical soiling (dust/ bird droppings), and maintenance access are useful for lifetime loss estimates.
10. Safety & working conditions
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Note egress for installers, where to stage materials, parking, and the availability of power/water on site for installation day.
Data capture: what to record (minimum)
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Photos (geotagged) of each roof plane and electrical equipment.
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Measured dimensions of each plane (m) and useful area (m²).
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Tilt & azimuth (degrees).
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Shading horizon plots or shading photos.
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Distance & route to meter/inverter location (m).
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Main service rating and panel free space.
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Roof material, age, and structure notes.
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Customer energy profile (kWh/day or monthly bills).
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Any permitting/HOA notes.
Use a standard survey form or checklist — this speeds design and quoting. (SafetyCulture, SepiSolar)
Quick yield & sizing calculation (worked example)
Example scenario (residential):
Customer average use = 12 kWh/day.
Site average GHI (from Global Solar Atlas for the locale) = 4.5 kWh/m²/day (typical value; use your site point when designing). (Global Solar Atlas)
Assume total system losses (derate) = 14% (PVWatts default → Performance Ratio PR = 1 − 0.14 = 0.86). (PVWatts Calculator)
We need to estimate the required DC array capacity (kW_p).
Step-by-step math (digit-by-digit):
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Compute effective daily yield per kW_p:
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Multiply GHI by performance ratio:
4.5 × 0.86
= (4.5 × 86) / 100
= (4.5 × 86) = 4 × 86 + 0.5 × 86 = 344 + 43 = 387
Divide by 100 → 3.87 kWh/day per kW_p.
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Required kW_p = energy need / yield per kW_p:
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12 kWh/day ÷ 3.87 kWh/day per kW_p
First, 3.87 × 3 = 11.61. Remainder = 12 − 11.61 = 0.39.
0.39 ÷ 3.87 ≈ 0.10078.
So required kW_p ≈ 3 + 0.10078 = 3.10078 kW_p → round up to 3.11 kW_p.
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Panels required (using 410 W modules):
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3.10078 kW ÷ 0.410 kW/module = 3.10078 ÷ 0.41
0.41 × 7 = 2.87 (remainder 0.23078).
0.41 × 8 = 3.28 > 3.10078, so we need 8 modules (total nameplate = 8 × 410 W = 3,280 W ≈ 3.28 kW_p).
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Takeaways from the example: with 4.5 kWh/m²/day and 14% losses, about 3.1 kW_p of PV meets 12 kWh/day; with 410 W panels you'd use 8 panels. Use the precise GHI and loss assumptions for final sizing. (Global Solar Atlas, PVWatts Calculator)
Converting the survey to a design & quote
From the recorded data you should produce:
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Site survey report — photos, shading maps, measured dimensions, roof & structural notes, electrical photo log.
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Preliminary single-line & layout — proposed panel layout per roof plane, mounting layout, inverter/battery location, cable routes.
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Preliminary stringing & inverter selection — choose inverter(s) based on DC/AC ratio, string voltage/current limits, and shade mitigation (optimizers or microinverters if shading is present).
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Estimate of energy yield — run PVsyst/HelioScope/PVWatts with the measured GHI and shading to get monthly yield and performance ratio. (PVWatts default losses = 14% is a good baseline.) (PVWatts Calculator)
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BOM & cost estimate — panels, inverters, mounting, wiring, combiner boxes, protections, labour.
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Permitting checklist — list of required permits and documents.
Practical tips & pitfalls
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Shading kills value. Even small obstructions can create hot-spots or string mismatch losses; consider module-level power electronics if shading is unavoidable. (SepiSolar)
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Measure twice. Satellite images are great but final rack placement must match rooftop obstructions and flashing.
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Use realistic loss assumptions. PVWatts default 14% is a sensible starting point; adjust for site-specific soiling, temperature, mismatch, and wiring losses. (PVWatts Calculator)
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Account for thermal effects. Hot climates reduce module output — factor temperature coefficients into your simulation. (Model this in PVsyst or PVWatts.)
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Document everything. Photos and measurements speed permitting and reduce RFI disputes later.
Deliverables you should hand the customer
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One-page system summary (capacity, expected monthly yield, payback estimate).
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Detailed site survey report (photos, measurements, shading plots).
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Proposed layout & single-line diagram.
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BOM & firm quotation with optional components (optimizers, batteries).
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Permitting & interconnection checklist.
References & authoritative resources
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Global Solar Atlas — solar resource maps and GHI data (use for initial site GHI). (Global Solar Atlas)
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NREL PVWatts — simple production estimates and default loss assumptions (14% default loss). (PVWatts Calculator)
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SepiSolar / SafetyCulture — practical solar site survey checklists and templates. (SepiSolar, SafetyCulture)
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NABCEP documentation — inspection and professional job task analysis for PV installers (guidance on inspection items). (NABCEP)
Frequently Asked Questions (FAQs)
Q1 — How long does a site survey take?
A thorough residential survey typically takes 45–90 minutes on site (depending on roof complexity) plus 1–2 hours for desktop prep and 1–2 hours to produce the survey report and tentative layout.
Q2 — Do I need a structural engineer?
If the roof is old, shows rot, or you plan to substantially increase load (large ground mount, heavy ballast systems), get a structural sign-off. Many jurisdictions require it for large systems.
Q3 — What tool gives the most accurate shading analysis?
Solar Pathfinder and Solmetric SunEye are field-proven for horizon/shade mapping. For final energy modeling, import measured shading into PVsyst or HelioScope for time-series simulation. (SepiSolar)
Q4 — How accurate are desktop irradiance maps?
Global Solar Atlas and NREL resources are excellent for a first estimate; local microclimates or persistent seasonal haze can cause deviations — that’s why on-site shading and temperature checks are essential. (Global Solar Atlas, NREL)
Q5 — Should I over-size the array relative to the inverter?
A modest DC:AC oversize (e.g., 1.1–1.3 ratio) is common to improve energy harvest (panels produce at rated power only near STC); check inverter manufacturer limits and local rules.