Do Solar Panels Cause Glare?

 

Solar panels can reflect some sunlight, but the amount is normally considerably less than might be expected from a large area of glass.

The principal purpose of a photovoltaic panel is to convert sunlight into electricity. Reflecting sunlight away from the panel would therefore reduce its effectiveness, which is why manufacturers generally seek to minimise reflection.

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Modern panels commonly incorporate anti-glare or anti-reflective solar glass to increase light transmission through the surface and into the photovoltaic cells below.

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Even so, no conventional solar panel absorbs 100% of the light falling onto it. A proportion can be reflected, particularly when sunlight strikes the panel at a shallow angle.

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Whether that reflection becomes noticeable elsewhere depends heavily upon geometry.

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What Causes Solar Panel Glare?

 

Solar panel glare occurs when direct sunlight reaches the surface of a photovoltaic panel and is reflected towards an observer.

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Three things therefore have to align:

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the position of the sun, the angle and orientation of the solar panel, and the position of the person or property receiving the reflection.

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Because the position of the sun continually changes throughout the day and throughout the year, any glare that does occur will often only be visible during particular periods.

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For example, a neighbouring property might potentially receive reflected sunlight for a short period during an early summer evening but experience no reflection during the remainder of the day or year.

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This is why simply looking at the direction a solar array faces does not necessarily establish whether glare will occur.

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Solar Glare and Neighbours

 

One of the most common concerns with domestic solar installations is neighbours' solar panel glare.

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This can arise where solar panels are installed on a roof facing towards another dwelling or where neighbouring buildings sit at different levels.

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Potentially sensitive areas can include:

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• bedroom and living-room windows

• balconies and terraces

• neighbouring gardens

• conservatories

• home offices

• elevated properties overlooking the solar array.

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In most situations the effect is limited because the reflected sunlight needs to reach the neighbouring property at precisely the correct angle.

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Nevertheless, glare should be considered where a large solar installation is proposed unusually close to neighbouring accommodation or where the site arrangement makes reflection particularly likely.

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Solar Glare Analysis

 

A solar glare analysis examines the relationship between the solar array, the movement of the sun and surrounding receptors.

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Computer modelling can be used to calculate whether sunlight reflected from the proposed panels could reach particular locations.

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The assessment may consider the:

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Panel orientation

The compass direction in which the solar panels face has a major influence on where reflected sunlight could travel.

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Panel pitch

A change of only a few degrees in panel angle can alter the direction of reflection.

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Position of the sun

The height and direction of the sun varies continuously according to the time of day, season and geographical location.

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Surrounding buildings

Windows, balconies and gardens around the proposed installation may be assessed as potential receptors.

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Roads and transport infrastructure

Solar installations close to major roads, railway infrastructure or airports may require more detailed consideration because glare could potentially distract drivers, train operators or pilots.

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The resulting solar glare analysis can identify whether glare is predicted, how frequently it may occur and whether alterations to the proposed installation would reduce the effect.

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Solar Glare and Planning Permission

 

For a typical domestic rooftop solar installation, solar glare will rarely be the deciding planning issue.

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However, the potential effect of reflected sunlight may receive greater attention where panels are proposed in unusual or sensitive locations.

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This may include large arrays, elevated sites, installations close to neighbouring windows, ground-mounted solar panels, solar farms and sites close to transport infrastructure.

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Where planners identify a potential problem, they may request further information demonstrating that the installation will not create an unacceptable impact.

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Considering glare during the design stage can therefore prevent unnecessary complications later.

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Solar Farm Glare

 

Solar farm glare can require more consideration than glare from a normal residential installation because of the scale of the photovoltaic array.

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A solar farm may contain thousands of panels extending across a large area of land.

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Even though individual panels have relatively low reflectivity, the size and position of the overall installation means that potential effects on nearby receptors may need to be assessed.

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Particular attention may be given to:

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nearby houses, public highways, railway lines, airports, airfields and other sensitive locations.

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A formal glare assessment can model the proposed solar farm throughout the year and identify whether particular receptors could experience reflected sunlight.

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PV Glare Near Roads

 

Road safety is another reason why PV glare may occasionally need to be assessed.

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A solar array positioned near a road could theoretically create a reflection within a driver's field of vision.

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The likelihood depends upon the relationship between the road, solar panels and movement of the sun.

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For small residential installations this is rarely significant, but larger ground-mounted schemes positioned close to major roads may justify a more detailed assessment.

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Where a risk is identified, the design of the array can often be modified before installation.

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Solar Panels Near Airports

 

Solar developments close to airports and airfields can receive particular scrutiny.

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Aviation-related solar glare assessments examine whether reflections could potentially affect pilots approaching or leaving an airport or personnel working within an air traffic control tower.

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This does not mean that solar panels cannot be installed near airports. Solar installations already exist at many aviation sites.

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It simply means that careful assessment can be necessary where the location and scale of an installation create the potential for reflected sunlight to enter important lines of sight.

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Anti-Glare Solar Panels

 

Many modern photovoltaic panels could effectively be described as anti-glare solar panels because manufacturers already take steps to minimise surface reflection.

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Panels commonly use textured glass and anti-reflective coatings that allow more sunlight to enter the panel.

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Reducing reflected light also improves panel efficiency, so there is a commercial reason for manufacturers to continually improve anti-reflective technology.

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If glare is a particular concern on a proposed installation, the specification and reflectivity of the chosen panel should form part of the design assessment.

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Can Solar Panel Glare Be Reduced?

 

Where a potential glare issue is identified, relatively small design changes can sometimes solve the problem.

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Options can include changing the pitch of the panels, adjusting their orientation, relocating part of the array or choosing panels with improved anti-reflective properties.

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For ground-mounted installations there may also be opportunities to adjust the height or position of the array.

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Landscaping or carefully positioned screening can occasionally help, although preventing the reflection through good panel design is usually preferable.

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The earlier solar glare is considered, the easier these adjustments tend to be.

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Is Solar Panel Glare Usually a Problem?

 

For the overwhelming majority of normal domestic installations, solar panel glare is unlikely to be a significant issue.

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Photovoltaic panels are intentionally designed to capture light and modern solar glass reflects relatively little of the sunlight reaching it.

However, every property is different.

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Unusual roof angles, neighbouring buildings at different heights, large ground-mounted arrays or sensitive nearby uses can justify closer examination.

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The important point is that solar glare can be predicted.

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Where there is genuine uncertainty, a solar glare assessment can establish whether a proposed installation is likely to cause a problem before the panels are installed.

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Planning a Solar Panel Installation?

 

A well-designed solar installation should consider more than simply how many panels can be fitted onto a roof.

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Panel orientation, pitch, shading, appearance, electrical performance and the relationship with neighbouring properties should all form part of the overall design.

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Where solar glare could potentially affect neighbouring homes or other sensitive locations, this can be considered during the planning and design process.

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APN Solar can help homeowners connect with experienced solar specialists who can assess the property, recommend an appropriate solar system and consider any site-specific issues before installation.

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