Solar panels, pitched roofs and risk of fire spread

1 60% increase in solar panel fires
2 Fire spread over pitched roofs fitted with solar panels
3 Calls for inclusion of electrotechnical expertise
4 Related articles on Designing Buildings

[edit] 60% increase in solar panel fires

In November 2025 global business insurer QBE revealed that the UK fire services were facing a fire involving a solar panel once almost every two days in 2024, which marked a 60% increase over the past two years (2022-2024). Their research also highlighted that the majority of incidents involving a solar panels took place in residential buildings during 2024, with 97 residential building fires, 27 commercial property fires, 17 Solar farms and 10 industrial buildings (Source: QBE FOI. Aug 2025).

Adrian Simmonds, practice leader for property risk solutions at QBE Insurance said: “Solar technology is an essential part of the UK’s clean energy transition, but the rapid pace of deployment is cause for concern for risk management. Our analysis shows fires involving solar panel fires have risen at twice the rate of new installations over the past two years. Safe solar panel installation and maintenance are essential to reducing fires. We strongly encourage property owners to carry out formal risk assessments, engage certified installers, and ensure regular inspections and cleaning. These simple steps can significantly reduce the chance of fire.”

The report concluded that improper installation was a frequent cause of fire, with loose connections, damaged wires, or faulty wiring leading to arc faults or other electrical issues. Other factors included component defects, high current, and external factors such as moisture, extreme weather, and dirt or foliage on the panels. The FoI data suggested that the majority of fires originate in the inverter or on the solar panels themselves.

By example the origin of solar panel fires in 2024 were 21 in the inverter, 20 on the solar panel, 16 from DC cabling and 12 fires originating with the battery bank (Source: QBE FOI (Aug 2025). The inverter is the hardest-working component in a solar panel system, prone to failure if installed incorrectly or poorly maintained. It generates significant heat, meaning poor ventilation, dust build-up, or blocked cooling systems can quickly elevate fire risks. Solar panel inverters can be positioned indoors and outdoors, but there should be no obstruction, good ventilation and timely replacement.

Adrian Simmonds went on to say “Most new domestic and commercial systems now include battery storage, introducing additional fire risks when units are installed in lofts, airing cupboards or upper-floor spaces that are difficult to access in an emergency. Combined with limited inspection and cleaning, these installations increase the likelihood and potential severity of fires.”

[edit] Fire spread over pitched roofs fitted with solar panels

The inverter is the hardest-working component in a solar panel system, prone to failure if installed incorrectly or poorly maintained. It generates significant heat, meaning poor ventilation, dust build-up, or blocked cooling systems can quickly elevate fire risks[3]. Solar panel inverters can be positioned indoors and outdoors, but there should be no obstruction, good ventilation and timely replacement.

On 22 December 2025 Government research and analysis on "Fire spread over pitched roofs fitted with solar panels" was published. The aim of the work, which involved 11 large-scale experiments was to study how the installation of photovoltaic (PV) panels affects the fire spread over pitched roofs in residential buildings. It was commissioned by the Building Safety Regulator’s (BSR) technical policy team, and conducted at the Health and Safety Executive’s Science and Research Centre, to inform if additional guidance is needed in Volume 1 of Approved Document B, the statutory fire safety guidance under the Building Regulations 2010 in England

Prompted by earlier incidents and experimental evidence indicating that photovoltaic (PV) installations can increase roof-level fire spread, BSR was concerned about the potential for fire to spread across roofs, breach compartment lines, affecting neighbouring buildings, and enter buildings via features such as rooflights. As such it focussed on design features of Building applied photovoltaic (BAPV) panels or Building integrated photovoltaic (BIPV) panels that influence fire spread, and capturing empirical data to improve understanding of the associated fire behaviour,.

BAPV systems showed that plastic-backed PV panels (Class C) allowed significant vertical fire spread up the panel array, although horizontal spread and fire transfer between adjacent panels was limited. Glass-backed panels (Class A) exhibited much lower fire involvement, with flames largely confined to the immediate ignition area and not spreading beyond the first panel. In contrast to this a plastic roof tiles system that achieved the highest European and UK fire standard BROOF (complete system assessment that can withstand fire penetration, resist spreading flames, and prevent burning droplets for at least 60 minutes) was a also tested with PV above. In this sample there was rapid and extensive fire spread beneath the array, producing large flames above roof level, though the aluminium support rails along panel edges acted as partial fire breaks by deflecting flames away from the rear of the panels, thereby slowing upward fire spread.

BIPV showed that systems incorporated wooden battens and plastic trays provided a substantial fuel load, resulting in significant vertical and horizontal flame spread, with flames extending beyond the roof line in all plastic-tray systems. The bespoke integrated system exhibited reduced vertical flame spread, likely due to a smaller fuel load within the cavity beneath the panels. Fires in BIPV systems were notably harder to extinguish than above-roof systems because flames could spread within sealed cavities behind the waterproof layer, limiting water access unless materials were breached, a finding of relevance to fire-service operations. An experiment above plastic roof tiles (also BROOF(t4) certified without PV panels) demonstrated the greatest flame spread, with rapid fire involvement beneath the panels and large flames above the roof. Additionally, the position of support rails influenced fire behaviour, as aluminium mounting rails around panel edges acted as fire breaks by deflecting flames away from the rear surface of the panels.

Following the initial test programme, four additional tests have been commissioned to address key findings. One test will assess the plastic roof tiles used in sample 4 without PV panels, enabling direct comparison of flame spread with and without solar panels present. The extensive flame spread and involvement of roofing materials observed in the BIPV tests also highlighted the potential risk of fire penetrating into the building, prompting further investigation. The remaining three tests will therefore examine fire penetration in BIPV systems using a more representative roof construction built over rafters rather than an oriented strand board deck, and will evaluate the effectiveness of fire-retardant breather membranes with three different reaction-to-fire classifications (Class E, B, and A2) in limiting fire spread into the building.

[edit] Calls for inclusion of electrotechnical expertise

Following the publication of its Warm Homes Plan which has a strong focus on increasing UK solar installations along with battery systems alongside its Warm Homes Plan Workforce Taskforce. The Electrical Contractor's Associaton (ECA) has called for urgent inclusion of electrotechnical expertise. It urged the Government to revise the composition of the Workforce Taskforce to ensure that electrotechnical experts play a central role in shaping training pathways, setting competency standards, and guiding the implementation of the Plan. It also called for targeted investment in apprenticeship programmes, support for training providers, and structured collaboration with the wider built environment sector to ensure that workforce capability is not an afterthought, but a foundation.