Quick answer
A report documenting shading effects on solar resource across specified roof areas or module positions, with stated evidence, metrics, and analysis period.
What is a roof shading report?
A roof shading report documents how modeled or measured obstructions affect solar resource on specified roof areas or proposed module positions over a stated period. It may include solar-access values, seasonal plots, obstruction maps, and related resource metrics. It supports layout and evidence review, but does not by itself establish electrical production, structural suitability, financial return, or permit acceptance.
Check what was analyzed before interpreting the numbers: the entire roof, selected roof planes, or only the proposed array. A report may leave other areas unevaluated. Colors have the meaning defined in that report’s legend; there is no universal green, yellow, or red viability scale.
Solar Access, TOF and TSRF measure different things
Solmetric’s definitions and Aurora’s shade-report documentation distinguish these resource comparisons. Verify the selected tool’s weather, reference orientation, time period, and aggregation method before comparing results from different systems.
| Metric | Resource comparison | Interpretation |
|---|---|---|
| Solar Access | Shaded resource divided by unshaded resource for the same surface and period | The shading effect relative to that surface’s unshaded case |
| Tilt and Orientation Factor, TOF | Unshaded resource at the actual tilt and orientation divided by the optimal reference | The orientation effect in the stated model |
| Total Solar Resource Fraction, TSRF | Shaded actual resource divided by the optimal unshaded reference | Shading and orientation effects together |
Expressed as percentages, TSRF (%) = Solar Access (%) × TOF (%) ÷ 100. Multiply fractional inputs directly only when they are represented as fractions rather than percentage numbers.
Solar Access and TSRF are not interchangeable. A roof can have no modeled shade while its orientation differs from the optimal reference. Neither metric is module conversion efficiency, guaranteed AC output, or the percentage of the customer’s electricity bill covered by solar.
For a fuller interpretation and worked calculation, use how to read a solar shade report.
What evidence should the report contain?
A useful report makes the site, model, and displayed result traceable. Request the information needed for the actual project decision rather than assuming every report follows one standard template.
| Record | What to check |
|---|---|
| Site and revision | Correct address or coordinates, roof planes, current layout, and report version |
| Data provenance | Imagery or survey source, capture date where available, processing date, and field corroboration |
| Obstructions | Buildings, roof equipment, parapets, trees, terrain, row geometry, and unresolved features |
| Geometry | Roof tilt and orientation, object heights, positions, and uncertainty |
| Time and resource basis | Weather or irradiance model, evaluation period, time convention, and calculation interval |
| Metrics and legend | Definitions, units, reference case, coverage, and aggregation method |
| Model limits | Assumed vegetation, missing geometry, exclusions, diffuse-light treatment, and unresolved checks |
| Review status | Permitted use, responsible reviewer, required next evidence, and revision trigger |
An annual average can conceal where and when shading occurs. Review roof-plane or module-position results and seasonal patterns when they affect placement. A lower winter access ratio indicates a modeled shading effect relative to the same period’s unshaded resource; shorter days alone do not explain that ratio. The important season depends on the location and actual obstructions, not a universal winter rule.
How is a roof shading report prepared?
The workflow combines geometry, solar position, resource assumptions, and a defined reporting method. Its accuracy depends on the sources and calculation, not simply on whether the output is a polished PDF.
- Establish current geometry. Identify the roof, surrounding obstructions, horizon, vegetation, and proposed modules using suitable remote data, drawings, measurements, or survey evidence.
- Define assumptions. Record dates, geometry uncertainty, vegetation state, resource data, time basis, and the reference case.
- Model or assess shading. Evaluate relevant shadow paths and solar-resource effects with a method suitable for the project’s purpose.
- Report the selected metrics. State which roof areas or module positions were analyzed and explain the legend, units, and limitations.
- Review and reconcile. Compare decision-changing inputs with current site evidence, correct conflicts, and update dependent layouts and calculations.
Near objects, distant horizon obstructions, and row-to-row shading can require different treatment. Weather variation, soiling, snow cover, equipment outage, and export curtailment should not silently be combined into a single roof-shade percentage. Identify which losses are inside each model output and which are handled separately.
Can a report be generated remotely?
Yes, suitable remote data can support a roof shading model. However, a visible photograph, surface model, and modeled sunlight layer are different sources. A remote report’s usefulness depends on data currency, geometry, object representation, and the decision it supports. Request field evidence when a consequential uncertainty cannot be resolved from the available sources.
Google’s Solar API reference distinguishes RGB aerial or satellite imagery, surface elevations, roof masks, solar-flux layers, and modeled hourly shade. It also distinguishes approximate imagery capture from processing completion. A recent download or processing date does not establish that the roof was photographed recently.
The satellite-image shading guide explains how to decide which remote questions still need corroboration. Do not claim that a remote source measures every vent, tree branch, or roof height simply because the rendering shows them.
Does a shade report predict electrical production loss?
A resource report alone does not determine the installed system’s electricity production. Electrical response also depends on modules, bypass behavior, strings, MPPT grouping, power electronics, operating temperature, and other model inputs. The energy simulation must use the same current layout and shade assumptions as the report.
Sandia PVPMC’s mismatch guide explains why interconnected devices can operate away from their individual maximum-power points: series paths share current and parallel paths share voltage. A fixed shaded-area percentage therefore cannot establish a universal string-output penalty.
Optimizers or microinverters may change electrical mismatch behavior within their documented operating limits. They do not remove an obstruction or create the irradiance it blocks. Compare feasible architecture and layout alternatives using consistent inputs, conversion losses, actual quotes, service access, and uncertainty instead of recommending module-level electronics from one resource threshold.
Is there a minimum acceptable solar-access value?
There is no universal solar-access percentage that proves a roof area is economical, selects an inverter, or establishes approval. A particular programme, lender, authority, or contract may specify a metric, threshold, report method, or accepted tool. Verify its current rules and the exact project scope before treating a number as an eligibility decision.
A layout choice also depends on structural capacity, access, fire and maintenance provisions, roof rights, electrical design, cost, tariff, consumption, and the customer’s objectives. A roof shade map helps assess one part of that decision; it does not override the other disciplines.
To evaluate a software workflow, review SurgePV’s shadow-analysis page and confirm the available methods and outputs for your site. A demo or report label does not establish permit, lender, or incentive acceptance.
Keep the report connected to the current design
Archive the source data, model assumptions, geometry, report, layout, and review status together. When a tree, neighboring building, roof feature, or array changes, identify the affected outputs and revise them. Keep the previous record for comparison rather than leaving an old report attached to a new proposal.
For customer communication, show the source date, modeled objects, metric definition, current conclusion, and unresolved check. Show a financial effect only after the energy and financial calculations support it. A roof photograph alone cannot establish a lost-savings amount, and a shade report is not a guarantee against future underperformance.
Frequently asked questions
What is a roof shading report used for?
It supports assessment of solar resource on specified roof areas or proposed module positions. Designers use it to compare placements and identify shade-related questions. Its scope, evidence, and model must be checked before it is used in a production estimate, quotation, or application.
How is a roof shading report different from a shade report?
Roof shading report describes a roof-focused scope; shade report is a broader label that can also cover ground-mounted arrays or other site areas. The names do not establish different mandatory formats. Read the actual coverage, metrics, sources, and limitations.
Can shading reports be generated remotely?
Yes, suitable remote imagery and surface data can support a report. Their currency, geometry, and obstruction detail must be reviewed. Field evidence may still be needed when uncertain features affect a consequential decision; remote generation alone does not prove site verification.
Does low solar access mean microinverters are required?
No. Resource metrics do not by themselves select electrical architecture. Compare layout changes, valid string and MPPT arrangements, optimizers, and microinverters using exact compatibility, modeled energy, cost, service requirements, and project constraints.
Related Glossary Terms
About the Contributors
CEO & Co-Founder · SurgePV
Keyur Rakholiya is identified by SurgePV as its CEO and a company co-founder. His SurgePV author page lists only role information that can be tied to the public profile below; credentials, project totals, testing claims, media appearances, and speaking engagements are not asserted without retained evidence.
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Rainer Neumann is credited as an editorial contributor on SurgePV content. This profile does not assert engineering credentials, project totals, software-testing experience, education, speaking engagements, or media citations because independent verification evidence is not retained in the publication record.
