Shading Analysis in Solar Design: When and How to Review

Put shading checks before production commitments

A panel layout and its generation estimate should describe the same project. Shading analysis belongs at several design gates because early imagery, measured site geometry and final electrical connections usually arrive at different times. Each stage should answer a specific decision rather than repeat the same checklist.

This is an editorial workflow for reviewable decisions, not a mandatory regulatory schedule. Adapt responsibilities to project scale and local professional requirements.

1. Screen the site without treating imagery as a survey

Identify nearby buildings, trees, chimneys, rooftop equipment and potential row-to-row shading. Record the image source and date. A visible footprint does not establish obstacle height, and an older image may omit recent changes.

List the inputs that could change a decision: roof tilt, obstacle height, tree canopy extent, mounting height and available space. Assign someone to verify them. A preliminary model can support screening, but its output should remain labeled preliminary until material uncertainties are resolved.

PVsyst’s shading overview separates distant horizon obstructions from nearby objects casting shadows across the array. Check whether both are represented in the chosen model. Modeling one category does not establish that the other has been covered.

2. Check the geometry before interpreting losses

Confirm coordinate conventions, roof orientations, dimensions, module elevations and obstacle positions. Inspect representative seasonal and daily sun positions to catch an inverted roof plane, misplaced object or inconsistent height reference.

A shadow animation is a geometry check. It does not by itself quantify annual energy. A single winter shadow also cannot establish an annual loss percentage. Document which observations are site measurements and which remain estimates.

Use the pre-layout shading checklist for this earlier gate. The workflow here continues through simulation and release rather than repeating every field check.

3. Compare feasible layouts on a consistent basis

Preserve the same weather data, equipment assumptions and loss conventions when comparing arrangements. Identify each deliberate change, such as removing shaded modules or increasing row spacing. Keep access, setbacks and other design constraints separate from an energy-only optimization.

Hypothetical comparison: layout A has 20 kWp and modeled annual production of 25,000 kWh. Layout B has 18 kWp and 24,300 kWh. B produces 1,350 kWh/kWp, compared with A’s 1,250 kWh/kWp, but its total annual production is 700 kWh lower.

These invented values illustrate a decision, not measured performance or a shading-loss benchmark. Greater specific yield does not automatically mean greater total energy or better project economics. Compare the objective, installed cost, load alignment and constraints before selecting a variant.

4. Align module placement with the electrical model

Shadows reduce incident irradiance, while unequal illumination can also create electrical mismatch. Treat those effects distinctly. The PVsyst calculation documentation describes irradiance and electrical shading calculations and explains why module-level optimizers can recover only part of the losses.

Do not turn a solar-access percentage into an automatic inverter recommendation. Evaluate the actual equipment, connection arrangement, model support and cost. Changes to stringing can affect the result even when the roof image looks unchanged.

For a detailed example of model inputs, PVsyst’s Module Layout documentation connects individual module locations to their electrical assignments for mismatch calculations. Record the chosen method and its limits. Results from different methods should not be compared as though the methodology were identical.

5. Review the production report before releasing the proposal

Check that the report refers to the current scene, module count, equipment and string arrangement. Inspect monthly outputs and the loss breakdown, rather than copying only the annual total. Explain important limitations in the proposal using ordinary language.

The shade-report reading guide explains resource metrics and result interpretation. Keep its definitions distinct from the model’s annual AC-energy estimate. Do not apply a second generic shading deduction to a result that already includes modeled shading.

A useful release record identifies:

• The layout and electrical revisions used.
• The weather source and simulation method.
• The obstacle inputs that remain uncertain.
• The accepted production scenario and relevant exclusions.
• The reviewer and decisions requiring further verification.

Avoid labeling a model as a production guarantee. Where a tree dimension is uncertain and material, compare a bounded alternative geometry while leaving other inputs unchanged. The range is only as defensible as those assumptions; it is not a statistical confidence interval.

6. Revisit the model after material changes

Review alterations to module positions, obstacle dimensions, row spacing, mounting heights and electrical connections. Equipment substitution may also require model updates. Record whether the affected inputs change the estimate and who accepts the revised design.

During installation, compare the actual arrangement with the accepted design and record deviations. A rerun can assess the modeled energy effect, but it does not replace structural, electrical or interconnection approval.

For a software evaluation, ask a solar design workflow demonstration to show how your team would retain geometry, assumptions and outputs together. Confirm the available features with the product team and test a representative project. The useful outcome is a traceable revision, not an unsupported claim that software eliminates review.

Questions about shading review gates

When should shading analysis enter the solar design workflow?

Start during site screening, before fixing panel count or promising production. Refine the assessment with measured geometry and the electrical design, then rerun it after changes that affect shadows or module connections.

Is a shadow animation enough to estimate energy production?

No. An animation helps inspect geometry at selected times. An energy estimate also needs weather and irradiance inputs, a shading calculation and the applicable electrical model; one image cannot establish annual loss.

Which changes require a shading review?

Review changes to obstacle dimensions, roof orientation, module placement, row spacing, mounting height, string assignments or relevant equipment. Decide whether a rerun is needed from the affected model inputs and record the reason.

How should uncertain trees or neighboring structures be handled?

Record the measured or assumed geometry and its source date. Where a plausible change matters, compare a clearly labeled alternative scenario rather than presenting an unsupported future condition as certain.