Key Takeaways
- A horizon profile maps the angular elevation of obstructions surrounding a solar site
- It determines when the sun is blocked from reaching the array throughout the year
- Measured in azimuth (compass direction) and elevation (degrees above horizontal)
- Critical for accurate energy yield predictions, especially in complex terrain
- Can be captured with on-site tools, LiDAR data, or satellite-based 3D models
- Directly affects system sizing, panel placement, and financial projections
What Is a Horizon Profile?
A horizon profile (also called a horizon line or skyline profile) is a 360-degree angular map showing the elevation of all objects on the horizon as seen from a specific point on a solar installation site. It records how high buildings, trees, hills, and other obstructions rise above the horizontal plane at each compass direction (azimuth angle). When overlaid on a sun path diagram, the horizon profile reveals exactly when and for how long the sun is blocked from reaching the solar array throughout the year.
Horizon profiling is a foundational step in professional solar site assessment. Without an accurate horizon profile, energy production estimates can be off by 5–25%, depending on the severity and location of obstructions.
Two rooftops on the same street can have dramatically different horizon profiles. A tall evergreen tree 20 meters to the south can reduce winter production by 30% or more — and that loss won’t show up in satellite imagery alone.
How Horizon Profiling Works
Capturing and applying a horizon profile follows a systematic process:
Select Measurement Points
Choose representative locations on the roof or ground mount area. For residential systems, measure from the center and edges of the proposed array area.
Capture Horizon Data
Use a Solar Pathfinder, SunEye device, smartphone app with compass/inclinometer, or extract data from LiDAR/3D models to record elevation angles at each azimuth.
Plot the Horizon Line
Map the elevation angles across all azimuths (0–360°) to create the horizon profile curve. Software tools generate this automatically from 3D site models.
Overlay Sun Path Diagram
Superimpose the horizon profile onto a sun path chart for the site’s latitude. Any sun path that falls below the horizon line represents blocked sunlight.
Calculate Shading Losses
The software calculates how much solar radiation is lost to horizon obstructions across each hour of the year, factoring in seasonal sun positions.
Adjust System Design
Use the results to reposition panels, avoid heavily shaded zones, or adjust tilt angles to minimize the impact of horizon obstructions.
Horizon Loss (%) = (Blocked Irradiance ÷ Total Available Irradiance) × 100Types of Horizon Obstructions
Different obstruction types affect the horizon profile in distinct ways. Understanding these helps designers interpret results correctly.
Terrain & Topography
Hills, mountains, and elevated terrain create fixed horizon obstructions. These are predictable and constant over the system’s lifetime. Most significant in valley and hillside locations.
Buildings & Structures
Neighboring buildings, chimneys, utility poles, and other structures cast shadows that vary by time of day and season. Urban environments typically have more building-related horizon obstructions.
Vegetation
Trees create horizon obstructions that change seasonally (deciduous) and grow over time. Designers must account for future growth — a 5-meter tree today may be 10 meters in a decade.
On-Site Objects
Parapets, HVAC equipment, satellite dishes, and adjacent panel rows on the same building. These are controllable through design choices and can often be mitigated with proper panel placement.
Always photograph the horizon from the proposed array location during a site visit. Photos serve as a reference to validate digital models and catch obstructions that satellite imagery may miss — like new construction or recently grown trees.
Key Metrics & Measurements
Horizon profiling relies on precise angular measurements:
| Metric | Unit | Description |
|---|---|---|
| Azimuth Angle | degrees (0–360°) | Compass direction of the obstruction (0° = North, 180° = South) |
| Elevation Angle | degrees (0–90°) | Height of the obstruction above the horizontal plane |
| Solar Access | % | Percentage of available solar radiation that reaches the array |
| Shading Factor | 0–1 | Fraction of time the sun is blocked at a given point |
| Annual Irradiance Loss | kWh/m²/year | Total solar energy lost due to horizon obstructions |
| Critical Azimuth Range | degrees | The azimuth range where obstructions affect peak production hours |
Solar Access (%) = (Actual Site Irradiance ÷ Unobstructed Reference Irradiance) × 100Practical Guidance
Horizon profiling affects multiple roles in the solar workflow. Here’s guidance for each:
- Use 3D modeling for accurate horizon data. Shadow analysis software that builds 3D models from LiDAR or satellite data automatically generates horizon profiles without requiring a site visit.
- Focus on the south-facing horizon. In the Northern Hemisphere, obstructions between 90° (east) and 270° (west) azimuth have the greatest impact on annual production. Prioritize accuracy in this range.
- Account for seasonal variation. A horizon obstruction at 15° elevation may block no sun in summer but block 2+ hours of direct sun in winter when the sun is low. Model all seasons.
- Validate digital models with site photos. Satellite and LiDAR data can be outdated. Compare the digital horizon profile against actual site conditions before finalizing designs.
- Capture horizon data during site visits. Use a Solar Pathfinder or smartphone compass app to record elevation angles at 15–30° azimuth intervals around the proposed array location.
- Note tree species and growth potential. Deciduous trees reduce winter shading when bare but will grow taller over the system’s 25-year lifetime. Evergreens shade year-round.
- Document neighboring construction. New buildings under construction or planned developments can dramatically change the horizon profile after installation.
- Flag marginal sites early. If horizon obstructions reduce solar access below 75%, discuss the limitations honestly with the customer and adjust expectations.
- Use horizon data to build trust. Showing the customer a detailed horizon analysis demonstrates thoroughness and differentiates you from competitors who skip this step.
- Explain shading impact in dollar terms. Instead of saying “you have 12% horizon shading,” translate it: “This shading reduces annual savings by approximately $180.”
- Address tree removal diplomatically. If trees are the primary horizon obstruction, present the production impact data and let the homeowner decide. Never assume they’ll remove trees.
- Highlight accuracy as a selling point. Accurate horizon profiling means the customer can trust the savings projections. “We guarantee our production estimates within 5%” is a powerful statement backed by thorough analysis.
Automated Horizon Analysis for Every Project
SurgePV’s solar shadow analysis software generates precise horizon profiles from 3D models — no site visit required for initial assessments.
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Real-World Examples
Urban Rooftop: Apartment Building Shadows
A residential installer in Berlin evaluates a south-facing rooftop surrounded by taller apartment buildings. The horizon profile reveals obstructions at 25–35° elevation between 150° and 210° azimuth — directly in the sun’s winter path. The shading analysis shows 18% annual irradiance loss. The designer repositions the array to the northern portion of the roof where horizon obstructions drop to 8° elevation, reducing losses to 6%.
Rural Ground Mount: Treeline Impact
A 50 kW ground-mount system in North Carolina faces a dense treeline 30 meters to the southeast. The horizon profile shows 20° elevation from 100° to 150° azimuth, blocking early morning sun from October through February. Annual production loss: 9%. The designer adjusts the array position 15 meters west and increases tilt by 5° to compensate, recovering approximately 60% of the lost production.
Mountain Valley: Terrain-Dominated Horizon
A residential system in the Swiss Alps sits in a valley with mountains to the east and west. The horizon profile reveals 30°+ elevation obstructions from 60° to 120° azimuth (east) and 240° to 300° azimuth (west). Effective sunlight hours are reduced from 8 to 5 hours per day in winter. The designer uses solar design software to optimize panel orientation for the available solar window, maximizing production within the constrained hours.
Impact on System Design
The horizon profile directly influences design decisions at every stage:
| Design Decision | Clear Horizon (Solar Access >95%) | Obstructed Horizon (Solar Access 75–90%) |
|---|---|---|
| System Size | Standard sizing based on consumption | May need to oversize to compensate for losses |
| Panel Placement | Full roof area available | Avoid zones with high obstruction angles |
| Inverter Selection | String inverters work well | Microinverters or optimizers handle partial shading better |
| Production Estimate | Standard derate factors apply | Must include specific horizon shading losses |
| Financial Projections | Higher confidence in savings | Wider uncertainty range — present conservative estimates |
When using solar software to design systems with significant horizon obstructions, always run the simulation with and without the horizon profile applied. The difference reveals the true production impact and helps justify design decisions to the customer.
Frequently Asked Questions
What is a horizon profile in solar design?
A horizon profile is a 360-degree map showing the angular elevation of all surrounding obstructions — buildings, trees, terrain — as viewed from a solar installation site. When overlaid on a sun path diagram, it reveals exactly when and for how long the sun is blocked throughout the year, enabling accurate energy production estimates.
How is a horizon profile measured?
Horizon profiles can be measured on-site using tools like a Solar Pathfinder, Solmetric SunEye, or smartphone apps with compass and inclinometer functions. Modern solar design software can also generate horizon profiles automatically from LiDAR elevation data or 3D models built from satellite imagery, often eliminating the need for a dedicated site visit.
How much does horizon shading reduce solar production?
The impact varies widely depending on obstruction severity and location. Minor horizon obstructions (5–10° elevation in non-critical azimuths) may reduce annual production by 1–3%. Significant obstructions (20°+ elevation in the south-facing arc) can reduce production by 15–25% or more, especially in winter months when the sun angle is low.
About the Contributors
Content Head · SurgePV
Rainer Neumann is Content Head at SurgePV and a solar PV engineer with 10+ years of experience designing commercial and utility-scale systems across Europe and MENA. He has delivered 500+ installations, tested 15+ solar design software platforms firsthand, and specialises in shading analysis, string sizing, and international electrical code compliance.
CEO & Co-Founder · SurgePV
Keyur Rakholiya is CEO & Co-Founder of SurgePV and Founder of Heaven Green Energy Limited, where he has delivered over 1 GW of solar projects across commercial, utility, and rooftop sectors in India. With 10+ years in the solar industry, he has managed 800+ project deliveries, evaluated 20+ solar design platforms firsthand, and led engineering teams of 50+ people.