Cut Energy Costs with Premium Rooftop Solar PV for UK Businesses

A solar PV system is a 25- to 30-year asset, so the roof beneath it must have a similar lifespan.

If your roof will need replacing within the next 10–15 years, it’s usually best to re-roof before installation to avoid future panel removal and re-installation. Our engineers always carry out a visual assessment as part of the feasibility process, but you probably have the best knowledge of its condition and whether it leaks or not.

Solar panels add around 10–15 kg per m² of PV panel additional weight, including mounting system and cabling. They can also trap more snow, adding to this weight during wintery conditions. The highest loading from the PV panels is actually from wind loading and this tends to pull them off the roof rather than add to the weight loading. In all cases, the mounting system must cope with is and the load will still be transferred to the underlying structure.

To withstand these loads the roof structure must be strong enough and be in good condition. Most modern steel-frame roof structures are easily strong enough, unless they are very lightweight construction or have been adapted from older agricultural buildings. Timber roofs can be fine but will need careful assessment. We review drawings, loading data, and – where necessary – undertake a structural assessment to confirm the roof can accommodate the system.

Some roofs are naturally better suited to solar PV than others:

Best options: Trapezoidal metal sheet roofs and standing-seam roofs. These allow fast, secure fixing with minimal penetrations.

Usable with care: Flat roofs (asphalt, bitumen, or membrane) can work using ballasted or non-penetrative systems, but they require careful design to avoid waterproofing damage. Great care must be taken to ensure that the weight of the solar PV system, including the ballast, doesn’t cause the roof to sag in the middle, creating a pond during wet weather.

Unsuitable: Asbestos-cement or fragile roofs cannot be worked on safely. These must be replaced before a PV system is considered.

The economics of commercial solar PV improve with scale. Each 1 kWp of panels requires roughly 4–5 m² of clear, unshaded roof area. Large, uninterrupted roof sections yield the best paybacks. Our drone 3D surveys and 3D design tools map usable roof space accurately, factoring in obstacles such as vents and skylights.

Rooflights, flues, and rooftop plant reduce usable space and can cause shading losses. We assess shading impacts hour-by-hour to optimise panel layout and avoid performance drop-offs. We generally include module-level power electronics (such as SolarEdge optimisers) to improve the overall performance, including to mitigate shading effects.

Safe installation and maintenance access are essential for compliance and insurance. We design and specify permanent edge protection, walkways and fall-prevention systems in line with HSE and insurer guidance. Good access ensures the system can be safely cleaned and inspected throughout its life.

South-facing roofs with a pitch between 10° and 35° deliver the best yields in the UK. East–west roofs can also perform well, spreading generation across the day and matching typical business demand.

Flat roofs can use tilted frames to achieve optimum orientation, though this increases cost and wind loading considerations.

You can even use north-facing roof slopes provided the pitch is less than 15°. These won’t perform as well as a south-facing orientation, but during summer when the sun reaches 60° above the horizon, the effective angle of incidence on the panels is then 45°, which is OK. On cloudy days, which let’s face it are quite common in the UK, orientation doesn’t make a great deal of difference. We would always recommend south facing first, then east or west, but if north is your only option and the pitch is shallow it could be viable. We can model the performance of any roof slope accurately so you can make an informed decision.

Proximity to the main electrical intake or distribution board reduces cable runs and losses. We also check grid capacity early in the project process through the G99 application process to ensure your site can export safely to the network if required.

All systems must meet current fire-safety, electrical, and structural standards (RC62, BS7672, and relevant DNO requirements). Our designs and documentation ensure your system remains compliant and fully insurable for the long term.