Solar Site Assessment and Shading Analysis in Georgia

A solar site assessment evaluates whether a specific property can support a productive photovoltaic installation, while shading analysis quantifies how obstructions — trees, roof peaks, neighboring structures, and chimneys — reduce the energy a system can generate over its lifetime. Together, these two processes determine whether a given roof plane, ground area, or canopy structure will yield acceptable energy output under Georgia's climate conditions. This page covers the definitions, procedural steps, common property scenarios, and decision thresholds that govern site assessment practice in Georgia.

Definition and scope

A solar site assessment is a structured technical evaluation that measures a location's suitability for solar energy generation. It encompasses roof condition, orientation, tilt angle, available unshaded area, structural load capacity, and proximity to utility interconnection points. A shading analysis is a subset of that process — a quantitative method for modeling how shadows cast at different times of day and across different seasons reduce annual solar irradiance striking the panel surface.

In Georgia, site assessments intersect with several regulatory frameworks. The Georgia State Minimum Standard Building Code, which adopts the International Building Code (IBC) and the National Electrical Code (NEC) (NFPA 70) by reference, governs structural and electrical requirements that a site must satisfy before installation proceeds. The Georgia Department of Community Affairs (DCA) administers the state's building code framework under O.C.G.A. Title 8. Local authorities having jurisdiction (AHJs) — typically county building departments — enforce these standards at the permit stage.

The page details how state and utility regulations shape installation requirements beyond the site assessment itself.

Scope and coverage limitations: This page addresses site assessment and shading analysis as practiced within Georgia's 159 counties under Georgia law and the state-adopted building and electrical codes. It does not address federal land installations, installations subject to Tennessee Valley Authority (TVA) service territory rules, or assessment methodologies governed by other states' codes. Utility-specific interconnection rules — governed by Georgia Power Company's tariffs filed with the Georgia Public Service Commission (PSC) — are addressed separately and are not fully covered here.

How it works

A complete site assessment follows a sequential, multi-phase process:

• Preliminary desktop review — Satellite imagery tools (such as those drawing on LIDAR datasets) are used to measure roof dimensions, identify visible obstructions, and estimate available surface area. Georgia's latitude ranges from approximately 30.4° N at the Florida border to 34.9° N at the Tennessee line, producing a solar resource that averages 4.5 to 5.5 peak sun hours per day depending on location, according to the National Renewable Energy Laboratory (NREL) PVWatts Calculator.
• On-site physical inspection — A technician measures roof pitch (typically expressed in rise-over-run, such as 4:12 or 6:12), verifies structural members and sheathing condition, identifies electrical panel capacity, and documents potential obstructions at ground level and above the roofline.
• Shading analysis with a solar pathfinder or equivalent tool — Devices such as a Solar Pathfinder, Solmetric SunEye, or software-based horizon profile tools generate a shade-free percentage figure. The most widely used metric is the Solar Access Value (SAV), which expresses the percentage of annual solar energy available at a point after shading losses. An SAV below 70% is generally considered a threshold below which residential installations lose cost-effectiveness, though this figure varies by system size and local utility rate structure.
• Structural load calculation — Roof framing must support the additional dead load of panels, typically 2.5 to 4 pounds per square foot (psf) for standard rack-mounted modules, in addition to existing snow, wind, and live load requirements under the ASCE 7 standard referenced by the IBC.
• Utility proximity and interconnection feasibility check — The assessment documents the distance from the proposed array to the main service panel and the meter, since runs exceeding certain lengths affect wire sizing under NEC Article 690. For grid-tied systems, the explains the interconnection pathway to Georgia Power or the relevant electric membership corporation (EMC).
• Report generation — The completed assessment produces a written report documenting all findings, typically including energy production estimates in kilowatt-hours per year, shading loss percentage by month, structural adequacy notes, and a go/no-go recommendation for permitting.

Common scenarios

Suburban residential roof installations represent the most frequent assessment scenario in Georgia. A south-facing roof plane at a 26° tilt (close to Georgia's optimal tilt angle near the geographic center of the state) with no obstructions within a 45° arc of the south-facing sky typically yields an SAV above 85%. Mature hardwood trees — especially oaks common throughout the Georgia Piedmont — are the most frequent cause of SAV reductions below the 70% threshold.

Agricultural properties in South Georgia often present large, unobstructed ground areas with high SAV scores exceeding 90%, making them candidates for ground-mounted solar systems in Georgia. Site assessment on agricultural land additionally involves soil bearing capacity tests and setback verification under county zoning ordinances.

Commercial flat roofs require assessment of rooftop HVAC equipment, parapet walls, and mechanical penthouses as shading sources. Unlike pitched residential roofs, flat roof systems use ballasted or mechanically attached racking at low tilt angles (5° to 15°), which reduces self-shading between rows but also reduces annual production compared to optimally tilted arrays.

Comparison — rooftop vs. ground-mount assessment: A rooftop assessment prioritizes structural adequacy, roof age (a roof with fewer than 5 years of remaining useful life typically triggers a replacement recommendation before installation), and NEC-compliant wire routing. A ground-mount assessment de-emphasizes structural analysis of an existing building but adds geotechnical considerations, grounding electrode system design, and longer DC or AC wire run calculations. The Georgia Solar Authority home resource provides navigational context for both installation types.

Decision boundaries

Site assessments produce binary or threshold-based outputs that determine whether a project advances to permitting or is modified.

Factor Typical Go Threshold Typical No-Go or Redesign Trigger

Solar Access Value (SAV) ≥ 70% annual < 70% annual

Roof age remaining ≥ 10 years < 5 years (replacement advised)

Roof pitch 10° – 45° tilt-equivalent < 5° (ponding risk) or > 50° (access and load issues)

Structural dead load capacity Sufficient for 3–4 psf added load Requires reinforcement per IBC/ASCE 7

Electrical panel headroom 20%+ breaker space available Full panel requiring upgrade

When an SAV falls between 70% and 80%, assessors may recommend tree trimming, alternative roof planes, or a reduced system size before a final permit application is filed. Tree removal in Georgia may implicate local tree ordinances — Atlanta's tree protection ordinance, for example, requires a permit for removal of trees above a specified diameter at breast height (DBH), which can affect shading mitigation plans on urban properties.

Permit applications submitted to Georgia county building departments must include site plans, structural calculations stamped by a licensed engineer (required in most jurisdictions when racking penetrates the roof deck), and a single-line electrical diagram compliant with NEC Article 690. The page covers permit submission requirements in greater detail.

Assessments that reveal structural deficiencies do not automatically disqualify a property. Ground-mount alternatives, solar carport and canopy systems, or community solar participation may remain viable paths even when the primary rooftop location fails assessment thresholds.

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References

• International Building Code (IBC)
• National Electrical Code (NEC)
• O.C.G.A. Title 8
• National Renewable Energy Laboratory (NREL) PVWatts Calculator
• ASCE 7 standard