Glare from PV systems on residents

Reflections from a photovoltaic system can reach living and working rooms, balconies and terraces in the neighbourhood. For residents, what matters is how often and for how long this happens. PV-GlareCheck calculates this duration for every observation point over a full year and provides the results as a basis for the expert assessment.

Guidelines

Germany – LAI. The notes of the German Federal/State Working Group on Immission Control (LAI) on light immissions contain recommendations on glare from photovoltaic systems in Annex 2 (as of 3 Nov 2015). As a point of reference for a significant nuisance, the guideline names an astronomically maximum possible glare duration of at least 30 min per day or 30 h per calendar year, taking all surrounding PV systems into account. For modules facing south, according to the LAI, locations mainly west and east of the system up to approx. 100 m away are potentially affected. The distance is a guide value; with large differences in height or extensive systems on a slope, locations further away can also be affected.

Austria – OVE R 11-3. The guideline was formally withdrawn on 1 Dec 2024 and is unofficially often still applied for orientation.

Switzerland – EnergieSchweiz/Swissolar. The guide to the notification and approval procedure for solar systems (edition June 2023) is a non-binding decision aid with reference values for duration and luminance.

None of the three guidelines is a law. Which guideline applies and how it is applied in the individual case is decided by the responsible expert and the competent authority.

Annex 2 of the LAI notes in detail: LAI guidance explained.

What PV-GlareCheck calculates

• every minute of the year with the sun above the horizon, under clear sky,
• glare duration per day and per year, number of days with glare and the glare times by date and time of day,
• luminance and illuminance at the observation point when a module type with a measured reflection profile is selected,
• occlusion by recorded buildings, embankments and vegetation and by the terrain from an elevation model,
• sun overlap and further filters, adjustable per group in the report without a new simulation.

Several storeys of a building are entered as separate groups with their own eye height. Existing neighbouring systems can be added as further PV areas.

Workflow

1. Enter the system, buildings and obstacles on the map; elevations from official terrain models where available.
2. Use the pre-analysis to check in which directions the system reflects.
3. Start the annual simulation.
4. Set the filters in the report according to the relevant guideline and export the result as a PDF.

Limits

The simulation is a model-based screening and does not replace an expert report. It assumes a clear sky; cloud cover shortens the real glare duration. The app does not check the location and distance rules of the guidelines automatically, and it does not assess the result.

Next: Settings, filters and a calculated example are described in the manual, chapter VI.1 Residents.