Shade Analysis
Shade analysis (or shading analysis) is the assessment of how shadows from nearby objects — trees, adjacent buildings, chimneys, roof features, terrain — affect the solar irradiance received by a PV array and the resulting reduction in energy production.
Shading is one of the most significant factors affecting real-world solar performance. Even partial shading of one panel in a string can reduce the entire string's output, making shade analysis critical for any site with potential obstructions.
Types of Shading
Near shading (local): Objects within 100m of the array — trees, chimneys, adjacent buildings, HVAC equipment. These cast distinct shadows with hard edges that move predictably with the sun.
Far shading (horizon): Distant terrain features (mountains, hills) that block the sun at low angles early morning and late evening. Primarily affects sites in valleys or with significant terrain elevation changes.
Self-shading: Row-to-row shading in multi-row ground-mount or flat-roof systems when rows are spaced too closely. Managed through row spacing design (ground coverage ratio).
Shade Analysis Methods
Simple visual assessment: Use satellite imagery (Site Studio) to identify shade obstacles and estimate their impact qualitatively.
Pathfinder / horizon analysis tools: Tools like Solmetric SunEye, Solar PathfinderApp, or drones with LiDAR measure the horizon profile at the panel location and calculate shading loss precisely.
3D modeling: Software like Helioscope, PVsyst's 3D shading module, or Aurora Solar creates 3D models of the site and simulates hourly shading throughout the year.
Shading Loss Guidelines
- Unobstructed (no shading): 0–2% annual loss
- Moderate shading (trees near roof edge): 5–15% annual loss
- Heavy shading: 15–30%+ annual loss
Heavy shading makes microinverters or power optimizers preferable to string inverters to minimize the impact on unshaded panels.