Glint and Glare for Rooftop Solar: When an Assessment Matters
Updated 23 October 2026 · SEO Dons Editorial
What are glint and glare, and do rooftop panels cause them?
The government's national policy statement for renewable energy defines glint as "a momentary flash of light that may be produced as a direct reflection of the sun in the solar panel". Glare is "a continuous source of excessive brightness experienced by a stationary observer located in the path of reflected sunlight from the face of the panel".
The same text begins with a reassurance: "Solar panels are specifically designed to absorb, not reflect, irradiation". It adds that panels "may reflect the sun's rays at certain angles", and that the effect occurs "when the solar panel is stationed between or at an angle of the sun and the receptor". So the question for a roof is geometric: where are the people, roads or aircraft that could sit in the reflected path? That policy statement was written for nationally significant solar farms, but it is an official description of how a glare assessment is structured, so this page borrows its definitions and method for rooftops.
When do the planning rules make you look at glare?
| Situation | Who asks, and what | Where it comes from |
|---|---|---|
| Roof array over 50 kW in England | The council, in the Class J(c) prior-approval determination on "design or external appearance", in particular glare on neighbours. | Class J, J.4(2) |
| Any Class J roof array in England | A condition to site equipment, so far as practicable, to minimise its effect on appearance and amenity. | J.4(1)(a) |
| Non-domestic roof array in Wales | A condition to minimise impacts from glint or glare, and a limit that panels are not within 3 km of an airport or aerodrome. | Welsh Government guidance |
| Roof array near an aerodrome | Aerodrome safeguarding may request an aviation glint and glare assessment, according to the CAA's FAQ. | CAA safeguarding FAQ |
In England the prior-approval step applies to "other solar PV equipment on the roof", the part of Class J above the 50 kW microgeneration ceiling in section 82 of the Energy Act 2004. The council "may require the developer to submit such information as the authority may reasonably require in order to determine the application", which is where a glint and glare study usually enters. England's Class J has no aerodrome distance condition of the Welsh kind, so a roof near an airfield is a matter for the aerodrome's own process, covered below.
When do aerodromes and roads come into it?
The CAA says it is "possible for solar installations and aerodromes to co-exist; in fact, some airports have their own installations", but they "need to be carefully assessed as depending on their location and overall size, they have the potential to deflect radar and can cause glint and glare". It adds: "In some circumstances we may request that a developer submits an aviation perspective solar hazard glint and glare assessment with their proposals."
Roof mounting adds its own aviation concern. The CAA notes that a roof-mounted installation has "the potential for it to infringe the Obstacle Limitation Surfaces (OLS) and to impact on Instrument Flight Procedures (IFPs) and Communication, Navigation and Surveillance (CNS) equipment". An aerodrome operator is "a statutory consultee for planning applications within the safeguarded zone", and the safeguarding map "generally covers a radius of 15km from the aerodrome". Whether a permitted development roof array reaches the operator through the council's process depends on the council, so a site inside that radius should approach the operator directly. Many aerodromes offer pre-application advice, and the CAA notes there may be a fee.
Roads and neighbours follow the same logic. The policy statement lists "nearby homes, motorists, public rights of way, and aviation infrastructure" as the receptors a decision-maker should assess.
What does an assessment model?
- Map the receptors. Applicants "should map receptors qualitatively to identify potential glint and glare issues and determine if a glint and glare assessment is necessary".
- Test the geometry. Where a full assessment is needed, applicants consider "the geometric possibility of glint and glare affecting nearby receptors" and assess impact "based on the angle and duration of incidence and the intensity of the reflection".
- Run it on the real layout. The policy statement says the analysis required "will depend on the specific project site and design", so a change to tilt, orientation or array position means a re-run.
- Recommend mitigation where a receptor is affected.
For example, take a hypothetical 2,000 square metre warehouse beside a dual carriageway, with a taller office block next door. The assessor would list the carriageway, the office windows and any nearby flight path as receptors, then calculate when, for how long and how intensely reflected sunlight could reach each one across the year.
How do designers reduce glare, and what should you ask for?
- Anti-reflective coating. The policy statement suggests panels "comprise of (or be covered with) anti-glare/anti-reflective coating". Historic England notes an anti-reflection coating can "reduce glare and reflection", often increases optical performance and "helps to reduce the visual impact as the panel appears less shiny".
- Screening between the panels and the affected receptor.
- Tilt and orientation. Adjusting azimuth or tilt "within the economically viable range" alters the angle of incidence, although "in practice this is unlikely to remove the potential impact altogether but in marginal cases may contribute to a mitigation strategy".
- Frames and supports add little: their glint and glare "is likely to be significantly less than the panels".
When comparing bids, ask for the receptor list, the module's coating specification, the tilt and azimuth the model assumed, and results by receptor. The commercial PV installations guide shows where this sits in a design stage, the England planning guide sets out the prior-approval timetable, and the 50 kW solar system guide covers what a system at that size involves. To put the same brief to several bidders, you can send an enquiry through the quote form.
Sources
- legislation.gov.uk, checked 22 October 2026: GPDO 2015 Schedule 2 Part 14; Energy Act 2004 section 82.
- GOV.UK (DESNZ), checked 22 October 2026: National Policy Statement for renewable energy infrastructure (EN-3), 2025, accessible webpage (in force 6 January 2026).
- Civil Aviation Authority, checked 22 October 2026: Combined Aerodrome Safeguarding Team FAQ.
- Welsh Government, checked 22 October 2026: solar panels mounted on a non-domestic building.
- Historic England, checked 22 October 2026: installing PV arrays on buildings.
Common questions
Does a small office roof need a glint and glare report?
Not as a rule. In England the prior-approval step covers arrays above the 50 kW microgeneration ceiling, so a smaller roof array is not put through that determination. The siting condition still applies, and a site near an aerodrome should check with the operator.
Who decides whether an assessment is needed?
For an English roof array over 50 kW, the council decides whether prior approval is required and can ask for information it reasonably needs. Near an aerodrome, the CAA safeguarding FAQ says an aviation assessment may be requested. The developer or building owner commissions the study either way.
Do frames and mounting rails cause glare too?
They can, but the national policy statement says the glint and glare of frames and supports is likely to be significantly less than that of the panels. An assessment can still include them where the site is sensitive.