solar panel supply chain provenance sourcing responsibly

The installation of solar panels is a win-win for housing. It cuts carbon emissions, reduces energy bills and lessens reliance on the grid. But, like so many things in life, there’s a bigger picture that must be considered when specifying solar panels. For example, solar supply chain provenance – understanding where solar panels and their components are manufactured and who makes them – is vital to the effective governance of sustainability and ethical practices throughout the supply chain.

Here at Marley, we are committed to responsible supply chain sourcing as part of our wider ethos within the Marshalls Group, and in particular through our sister company, Viridian Solar. Transparency, traceability and assessment are among our top priorities, and we hold our suppliers to high standards. Through a process of detailed mapping, in-person factory visits and independent audits, we have traced our silicon supply chain back to the raw materials, and we will continue this important work to provide further confidence that Marley solar products meet the highest social and environmental standards.

What are the challenges with the solar PV supply chain?

In 2023, the Marshalls Group roofing divisions, consisting of Marley and Viridian Solar, began the complicated task of tracing the provenance of our photovoltaic (PV) panels. In March 2025, we hit an important milestone, having visited every level of our solar cell supply chain and tracing the provenance of our PV panels all the way back to silica mining.

Silica is the raw material used to create polysilicon, which can conduct electricity when exposed to sunlight, making it an essential component of solar panels.

Dean Weldon, Sales Director at Marley, explains that over the last two years, members of the team have visited six Chinese provinces and encountered eight tiers of production:

• Tier 1 Panel assembly
• Tier 2 Cell manufacture and optimisation
• Tier 3 Wafer manufacture
• Tier 4 Ingot manufacture
• Tier 5 Polysilicon purification
• Tier 6 Metallurgical grade silicon production
• Tier 7 Silicon smelting
• Tier 8 Extraction, grading and cleaning of raw materials

While we haven't managed physical visits to every single entity in the supply chain yet, we have identified every producer in the first seven tiers of production. And we will continue our work to map out the remaining elements of the supply chain.

Commenting on the work so far, Dean says: “Visiting the various production sites in person has allowed us to meet with a wide range of businesses and gain a better understanding of the technology at every stage of the process.”

These visits have also allowed the Marley team to gain a clearer understanding of production methods and supply routes. “They also provide an opportunity for conversations about environmental standards, safety practices and technical controls,” he adds.

Responsible solar PV procurement

Along with our supply chain mapping, we’ve signed commercial agreements with our supply chain partners for the first five tiers of production, and about half of tier six. This means we have formal agreements specifying that materials can only enter the supply chain via agreed locations.

To ensure standards are being met, we’ve also rolled out a programme of independent third-party ethical audits of our Tier 1 and 2 suppliers, including cell and panel manufacturers, inverter producers and mounting system fabricators. These entities have all been assessed against the SA8000 social standard – a globally recognised social accountability standard, and they have all achieved ISO 9001, 14001 and 45001.

No major concerns have been raised during these audits, but the process has helped to support adjustments in environmental health and safety practices, as well as an improvement in working hours at some sites.

Building a better solar PV industry

We know supply chain due diligence is an ongoing process, not a one-time tick-box exercise. That’s why we continue to conduct supplier visits, extend commercial agreements and support the development of global standards.

We’re actively working with the Solar Stewardship Initiative (SSI) – a pan-European programme that is building international standards around traceability and ESG performance in solar manufacturing. As the solar sector grows, initiatives like this will help provide greater confidence and consistency for specifiers, developers and end users.

Dean notes that in the process of creating a more sustainable and ethical solar PV industry, Marley is just one piece of the puzzle, and he encourages others to also take steps to ensure that high standards are achieved across the construction sector. “From solar panel manufacturers, like us here at Marley, to specifiers, developers, social housing providers, local governments, housebuilders and installers – we all have a role to play in ensuring ethical provenance and responsible purchasing,” he says.

Marley’s efforts to ensure a responsible supply chain

The team at Marley takes great pride in all aspects of our ESG (environmental, social and governance) policies – and we are one of the few solar providers to have visited suppliers at every level of the supply chain, from silica mining to panel assembly. With more trips planned, we’re not stopping yet. Our goal is to eventually visit every supplier in the chain.

“Due diligence is an ongoing work in progress,” Dean notes. “The team at Marley is dedicated to keeping up with the changing procurement considerations, as well as our clients’ expectations,” he concludes.

Marley SolarTile®, our integrated roof PV panel, has been carefully developed to provide quality, safety and energy efficiency, and we have also worked hard to ensure that all elements are responsibly sourced.

If you have any questions about our supply chain, or to enquire about using our Marley SolarTile® on your next roofing project, please get in touch.