Site survey: roof orientation, shading, pitch
Solar Pv · Lesson 6 · Intermediate
Purpose
Conduct a PV site survey that joins solar-resource, structural, fire, electrical and safe-access evidence.
Learning objectives
- Interpret the governing data
- Calculate on a declared basis
- Identify design limits
- State uncertainty
Orientation and pitch matter, but a defensible survey also captures shading through time, usable geometry, structure, roof condition, wind, fire pathways, cable routes and electrical connection constraints.
Core theory
Record location, horizon/shading objects, azimuth, pitch, usable dimensions and exclusion zones. A single midday photograph cannot characterize seasonal shading.
A competent structural assessment addresses roof construction/condition, imposed loads, wind uplift, fixing zones and waterproofing. Survey access must not damage fragile roofs or expose people to falls.
Trace inverter/battery locations, DC and AC routes, earthing/bonding, supply/earthing system, meter/service equipment, consumer unit, network constraints, fire-service considerations and maintenance access.
| Term | Meaning | Symbol | Unit |
|---|---|---|---|
| Azimuth | Horizontal direction of module face | Not applicable | degrees |
| Pitch | Tilt from horizontal | Not applicable | degrees |
| Solar horizon | Angular obstruction profile around the site | Not applicable | Not applicable |
Assumptions: Areas do not overlap.
- Subtract: Preliminary unshaded usable area=24−6−4=14 m².
- Qualify: Module layout, fixing zones, wind and shading model still require validation.
- Boundary: Carry the result into the remaining product, safety and design-limit checks before selection.
Preliminary usable area is 14 m², not a completed array layout.
Reasonableness check: Exclusions reduce rather than increase gross roof area.
- Treating STC as guaranteed field output
- Using nominal values instead of exact datasheets
- Ignoring temperature, tolerance or mismatch
Where this appears in practice
Traceable PV design uses exact product data, site evidence and compatible worst-case assumptions.
Knowledge check
Can orientation and gross roof area alone approve an array?
No. Structure, wind, fire, shading, access and electrical constraints remain.
Answer: No. Structure, wind, fire, shading, access and electrical constraints remain.
Practical exercise
Complete a supplied site-survey checklist and raise missing-evidence actions.
Summary
- Conditions define the value
- Worst cases must be compatible
- Record sources and assumptions
Sources and review
- IEC 61215-2:2021: Terrestrial photovoltaic modules: test procedures: IEC; 2021; International
- HEM-TP-18 PV generation and self-consumption: UK Government; Current published methodology; United Kingdom
- PV research data and modelling tools: National Renewable Energy Laboratory; Current online resources; International research
Editorial review date: 2026-08-22. Professional electrical review is pending.