Solar Stewardship Initiative

What Solar Stewardship Initiative does

The Solar Stewardship Initiative (SSI) is an independent, multi-stakeholder certification scheme launched in October 2022 by SolarPower Europe and Solar Energy UK and operated in the United Kingdom by Assheton Carter Ltd (trading as TDi Sustainability). SSI develops and maintains two proprietary standards for the solar PV industry: the SSI ESG Standard (published October 2023), which evaluates manufacturing sites against 96 criteria covering Governance and Business Ethics, Environment, and Human and Labour Rights; and the SSI Supply Chain Traceability Standard (published December 2024), which uses a segregation-based Chain of Custody model to track silicon-based materials from quartzite mining through polysilicon, ingot, wafer, cell, and module production. Certifications are issued at Bronze, Silver, or Gold levels following site-level audits conducted by SSI-approved independent third-party Assessment Bodies (Intertek/CEA, DNV, KIWA, SGS, Sinovoltaics, TÜV SÜD, TÜV Rheinland) under an eight-step assurance cycle that includes private worker interviews and stakeholder consultations.

SSI generates revenue through tiered annual membership fees paid by Manufacturer Members (polysilicon, ingot, wafer, cell, and module producers), Buyer Members (developers, installers, and purchasers), and Association Members (industry trade bodies), supplemented by a Candidate Pathway tier for organisations working towards full membership. Membership is acquired via a structured application process including Secretariat due diligence, Board recommendation, Board approval, and fee invoicing; pricing is not publicly disclosed. SSI serves solar PV manufacturers with certified supply-chain obligations, downstream buyers needing verified responsible procurement, civil society and academic stakeholders through a Stakeholder Advisory Group and Technical Working Groups, and international financial institutions (IFC, EIB) that use SSI as a de-risking tool for solar project finance. As of early 2025, the initiative had over 50 member organisations representing more than 60% of globally shipped solar PV modules, 17 certified production sites with combined annual module capacity of 123 GW, and a forward assessment pipeline of 100 GW of modules and 20 GW of cells — supported by manufacturer binding commitments to source 80% (by January 2027) and 100% (by January 2028) of modules shipped to the EEA, UK, and Switzerland from SSI-certified sites.

Name

Solar Stewardship Initiative

Legal name

Assheton Carter Ltd

Website

https://solarstewardshipinitiative.org

Company type

Private

Founded year

2022

Operating status

Operating

Headcount range

1–10 employees

Short description

The Solar Stewardship Initiative is a UK-based multi-stakeholder certification scheme that operates the SSI ESG Standard and Supply Chain Traceability Standard for solar PV manufacturers, delivering site-level audits through approved third-party Assessment Bodies and serving manufacturers, buyers, civil society, and development finance institutions across the global solar value chain.

Ownership category

akta.pro rank

Product category

Sustainability and ESG Certification Services

NAICS

Testing Laboratories and Services (54138)

SIC

Services-Testing Laboratories (8734)

akta.pro primary industry

Solar Quality, Testing, Certification & Standards (Lab Testing, Inspections, Compliance) (EUAMABAN)

akta.pro secondary industries

Environmental, Climate & Sustainability Standards & Reporting Cooperation (BPADANAI), REC/GO Certification, Verification & Auditing (EAC Standards) (EUAMAKAB), Social Compliance & Labor Standards Certification (SMETA/SA8000) (AFALAMAM)

Keywords

• Solar supply chain certification
• ESG standard development
• Supply chain traceability assurance
• Solar industry due diligence
• Responsible sourcing certification

GTM type

B2B

Offering type

Services

Cost components

Personnel, Operations, Marketing or Sales, Technology or R&D

Revenue model

1. SSI Membership Fees: SSI generates revenue through membership fees paid by manufacturer members, buyer members, and association members. The membership application process requires payment of a membership fee invoice upon approval. Fee terms and conditions are documented in the SSI Membership Fee Terms and Conditions (published February 2026). The specific fee structure is not publicly disclosed on the website.

Pricing tiers

Go-to-market motion2 records

Distribution channels4 records

Marketing channels7 records

Core offering

The Solar Stewardship Initiative (SSI) develops and operates two sector-specific certifiable standards — the SSI ESG Standard (96 criteria across Governance, Environment, and Human & Labour Rights) and the SSI Supply Chain Traceability Standard (segregation-based Chain of Custody covering the full silicon value chain from quartzite to modules). These standards are delivered through an 8-step assurance cycle executed by SSI-approved independent third-party Assessment Bodies (Intertek/CEA, DNV, KIWA, SGS, Sinovoltaics, TÜV SÜD, TÜV Rheinland), which conduct site-level audits and award Bronze, Silver, or Gold certifications.

Product overview

The Solar Stewardship Initiative operates as a dual-standard certification and assurance system specifically tailored for the solar PV industry. The core offering consists of two mandatory certification standards: the SSI ESG Standard, which evaluates manufacturing site performance across Governance and Business Ethics, Environment, and Human and Labour Rights; and the SSI Supply Chain Traceability Standard, which tracks materials throughout the solar value chain using a segregation-based Chain of Custody model. These standards are implemented through the SSI Assurance Process, wherein independent third-party Assessment Bodies conduct site-level assessments and certify sites at Bronze, Silver, or Gold levels. The SSI Member Portal provides members with access to assessment summaries and resources, while supporting resources like the SSI Buyer's Guide and Core Documents (Assurance Manual, Claims Guide, etc.) support implementation and compliance.

Differentiator

Problem solved

Functional benefit

Products and services

• SSI ESG Standard An assessment standard that evaluates a solar manufacturing site's performance across 96 criteria in three areas: Governance and Business Ethics (5 principles), Environment (6 principles), and Human and Labour Rights (3 principles). Sites are certified by independent third-party Assessment Bodies at Bronze, Silver, or Gold levels.
• SSI Supply Chain Traceability Standard A standard that tracks the movement of goods, materials, and information through the solar supply chain from raw material source (quartzite/quartz) to module manufacturing, using a segregation-based Chain of Custody model. Certifications range from Bronze (traceability to polysilicon) to Gold (full traceability to quartzite mines).
• SSI Assurance Process An 8-step assurance cycle (membership due diligence, signing SSI Principles, self-assessment, Assessment Body selection and onsite audit, certification decision, publication of summary report, continuous improvement and surveillance, and three-year re-assessment) delivered by SSI-approved third-party Assessment Bodies. Assessments include document reviews, facility walkthroughs, unsupervised private worker interviews (up to 14 hours with 60+ workers), management interviews, and external stakeholder consultations.
• SSI Approved Assessment Bodies Network A network of independent third-party certification bodies approved by SSI to conduct site-level audits and certify member manufacturing sites against SSI Standards. Current approved ABs include Intertek (Clean Energy Associates), DNV, KIWA, SGS, Sinovoltaics, TÜV SÜD, and TÜV Rheinland.
• SSI Membership A tiered membership program with categories including Manufacturer Members (polysilicon, ingot, wafer, cell, module producers), Buyer Members (developers, installers, purchasers), Association Members (trade associations such as SolarEnergy UK, SolarPower Europe, Global Solar Council, Solar Ireland), and Candidate Pathway organizations. Membership includes access to certification, governance participation, and use of the SSI Member Portal.

Quantifiable outcome

• 17 certified solar production sites with combined annual module production capacity of 123 GW, 22.5 GW of cells, and 11 GW of ingots
• +3 more outcomes

Named customers11 records

Segments4 records

Ideal customer profiles3 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature5 records

Partnerships

Six partnerships are on record, tiered core and minor.

• Initiative for Responsible Mining Assurance (IRMA)coreStrategic or Co-development Partner · 3 April 2026The SSI and IRMA signed a Memorandum of Understanding (MoU) to strengthen cooperation on responsible mineral sourcing, supply chain transparency, and respect for human and workers' rights across solar supply chains, from mining through to solar module manufacturing. This partnership advances upstream verification in the solar supply chain.
• Solar IrelandcoreStrategic or Co-development Partner · 16 December 2025The SSI and Solar Ireland signed an MoU to ensure that the Irish solar market's rapid expansion is anchored in a commitment to responsible and sustainable practices across the entire solar value chain. Solar Ireland is an Association Member of SSI.
• The Copper MarkcoreStrategic or Co-development Partner · 27 November 2025The SSI and The Copper Mark signed an MoU providing a framework for collaboration promoting responsible production and sourcing of copper across the solar energy value chain. This addresses the use of copper in solar modules and related components.
• Global Wind Energy Council (GWEC)coreStrategic or Co-development Partner · 13 November 2025The SSI and GWEC signed an MoU to drive sustainability, transparency, and resilience across the solar and wind energy industries' supply chains. This cross-sector collaboration aims to share best practices and strengthen supply chain governance in renewables.
• TDi SustainabilitycoreImplementation/ SI/ Consulting Partner · 21 March 2025TDi Sustainability (trading as Assheton Carter Ltd) manages the SSI website, Member Portal, and provides operational support to the SSI Secretariat. The company is referenced in the website terms of use as the entity operating the SSI site on behalf of the initiative. TDi Sustainability conducted pilot assessments for the Supply Chain Traceability Standard in Q1-Q3 2024.
• Green Economy Coalition (GEC)minorStrategic or Co-development Partner · 26 February 2025SSI became a member of the Green Economy Coalition, the world's largest alliance dedicated to transforming economic systems for a greener and fairer future. GEC brings together businesses, trade associations, NGOs, UN agencies, and civil society groups to advocate for sustainable economic reform.

Scale indicators6 records

Recent moves8 records

Expansion highlights6 records

Direct peers

• Initiative for Responsible Mining Assurance (IRMA): IRMA provides independent third-party verification of mining operations and is now an SSI partner via a 2026 MoU. It is directly comparable as a sector-specific multi-stakeholder assurance scheme for upstream raw materials (quartzite, polysilicon feedstock) feeding into SSI's downstream traceability.
• Sedex: Sedex hosts one of the most widely used supply-chain ESG platforms (SMETA audits) used by solar manufacturers and buyers. It is a direct competitor for member mindshare and audit budgets in solar supply-chain ESG, though it is multi-sector rather than solar-specific.
• Fair Labor Association (FLA): FLA is a multi-stakeholder initiative that conducts independent assessments of labour conditions in supply chains. It is comparable as an accredited, third-party-audited labour-rights assurance scheme used by global brands and manufacturers, including in solar-adjacent electronics.
• The Copper Mark: The Copper Mark is a multi-stakeholder assurance framework for responsible copper production and a 2025 SSI MoU partner. It is highly comparable as a sector-specific certification scheme with independent third-party assessments, board representation from industry and non-industry, and a focus on raw-material ESG due diligence.

Regional players

• European Raw Materials Alliance (ERMA): ERMA is an EU-led alliance focused on securing access to critical raw materials, including those used in solar PV. It is comparable as a Europe-based multi-stakeholder initiative addressing upstream supply-chain resilience and ESG risks in materials feeding clean-energy technologies.
• Better Work Programme (ILO/IFC): Better Work is an ILO/IFC partnership providing factory-level assessments of labour conditions in garment and electronics supply chains. It is comparable as an IFC-affiliated third-party assurance programme; SSI overlaps conceptually given IFC's endorsement and shared focus on labour-rights verification at supplier sites.

Others

• AccountAbility (AA1000 Stakeholder Engagement Standard): AccountAbility develops the AA1000 series of standards for stakeholder engagement and ESG assurance. It is comparable as a standards-setter whose framework SSI's governance and assurance design references, and as an indirect peer in the sustainability-standards ecosystem.

Broad incumbents

• ISEAL Alliance: ISEAL is the global membership organisation for credible sustainability standards and codes of good practice. It is comparable as the meta-governance body whose Code of Good Practice SSI aligns with, and serves as a benchmark for scheme credibility, governance, and assurance.
• Responsible Business Alliance (RBA): RBA operates the Code of Conduct widely used for ESG and labour-rights assessments in electronics and solar supply chains. It is the closest broad-incumbent comparator to SSI: an industry-led multi-stakeholder assurance scheme, but spanning multiple sectors rather than solar-specific.

Emerging players

• Global Battery Alliance / GBA Battery Passport: The Global Battery Alliance operates the Battery Passport, a traceability and ESG disclosure scheme for battery materials. It is comparable as a multi-stakeholder, World Economic Forum-affiliated initiative building traceability into critical-mineral supply chains — a structural cousin of SSI's supply-chain traceability model.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks6 records

Key highlights7 records

Customer concentration

• LinkedInlinkedin.com/company/solar-stewardship-initiative

Revenue estimate

Valuation estimate

Number of profiles

Profiles11 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Solar Stewardship Initiative