Glare assessment for PV systems: process and cost

What a glare assessment is

A glare assessment determines whether, when and how strongly reflections from a photovoltaic system reach people in the surroundings, and evaluates the result against a guideline. Depending on the location, residents, roads, railway lines or aerodromes are considered. It is usually based on a simulation over a full year; the assessment is carried out by an expert.

When it is required

Whether an assessment is needed is decided by the competent authority in the procedure. Typical occasions:

• Neighbourhood: homes or building plots near a larger ground-mounted system, especially to the west or east with modules facing south (LAI notes, Annex 2, Germany).
• Federal trunk roads (Germany): According to the position paper of the Federal Highway Authority (FBA, as of November 2025), all systems that can be seen or potentially seen from the road must be examined. A glare report can be required, for instance if reflections towards the carriageway are possible; according to the paper, an expert statement is sufficient if permanent obstacles interrupt all lines of sight.
• Railway lines and aerodromes: at the request of the competent bodies; for aerodromes, the EASA guidance is often used.

Process

1. Request and scope: which receptors, which guidelines, which parts of the system.
2. Collect documents: system design, module data, surroundings (see below).
3. Build the model: enter the system, terrain, obstacles and observation points.
4. Simulation: reflections over a year; per observation point duration, times, angles and intensity.
5. Assessment: the expert classifies the results according to the relevant guideline.
6. Report and mitigation if needed: if results are conspicuous, measures such as screening, a changed orientation or tilt, low-glare modules or an adapted tracking strategy are examined and recalculated.

Required documents

A general compilation; for federal trunk roads, the FBA list of required documents (as of January 2025) applies in the individual case.

• site plan and module layout, orientation and tilt, height of the lower and upper module edge,
• for tracking systems: axis direction, rotation range, backtracking, stow and special positions,
• module data sheet; for luminance and beam spread, ideally a measured reflection profile of the module,
• terrain elevations, on slopes an elevation model,
• location and height of homes, roads, tracks or flight paths,
• permanent obstacles such as noise barriers, embankments, buildings.

What drives the cost

• Receptors and guidelines: residents, roads, railways and aerodromes differ in observation points and evaluation; several receptors or countries increase the effort.
• Size and structure of the system: number of sub-areas, different orientations, dual orientation, tracking.
• Number and type of observation points: storeys per building, length of routes, directions of travel, vehicle types, approaches.
• Terrain: flat ground or slopes with cross slope and terrain occlusion.
• Data situation: completeness of the design documents, availability of a measured reflection profile, official elevation data at the site.
• Variants: comparison of orientations, module types or mitigation measures.
• Result: the more reflections occur, the more detailed the assessment and its presentation in the report.
• Coordination: queries from the authority and additions.

What a simulation does and does not do

A simulation provides duration, times, direction and intensity of reflections for every observation point. It is a model-based screening and does not replace an expert report: it assumes a clear sky, treats obstacles as unchanged throughout the year and does not assess the result. Before use in permitting and planning procedures, the results must be reviewed by qualified professionals.

Cost of the simulation with PV-GlareCheck

PV-GlareCheck is aimed at planners and experts who carry out the simulation themselves. A project is created with a project token and receives simulation tokens; each simulation uses one of them, regardless of the number of areas and points. Pre-analysis, filters and changes in the report do not use a token. The Pro plan extends limits and features. Every account can create one demo project free of charge. Current prices are listed under pricing and plans.

Next: Use cases residents, roads, railways and air traffic; general notes in the manual, chapter VI.5.