Supermarket supplier audits in 2026: how farm solar supports Scope 2 disclosure

UK supermarket Scope 3 ambition has flowed downstream to supplier Scope 2 disclosure over the last three years. In 2026, every major UK retailer has at least some flavour of supplier-level emissions reporting in its supplier agreements, and on-farm renewable generation is increasingly cited as material in supplier audits. Here’s how it plays out across the major retailers and what it means for working farms.

The retailer-by-retailer picture

Tesco Stronger Starts: Includes supplier Scope 1+2 disclosure requirements rolled out over 2023–2025. Tesco published its own SBTi-validated Scope 3 targets in 2022 and the supplier programme cascades them. Farm suppliers (direct fresh produce, dairy via Müller Direct, eggs via Stonegate, meat via various contract processors) are increasingly asked to demonstrate Scope 2 reduction year-on-year. On-farm solar generation evidence (kWh generated, kWh consumed on-farm, kWh exported) is auditable Scope 2 reduction.

Sainsbury’s Plan for Better: Includes a comprehensive supplier sustainability framework with Scope 2 emissions disclosure for major suppliers. Sainsbury’s Dairy Development Group (SDDG) has its own sustainability protocol for milk producers. Solar generation is documented in the annual SDDG return.

M&S Plan A: Long-established programme, has carried supplier sustainability requirements since 2007. M&S Select Farms (their fresh produce supplier programme) and M&S Select Farms Dairy carry explicit renewables-and-efficiency expectations. Solar installations are documented at the farm level and feed into the M&S supplier sustainability scorecard.

Waitrose First Generation Farm Standards: Waitrose’s flagship supplier programme has carried environmental ambitions since the early 2010s. Renewables-on-farm has been a tracked metric since 2016 with annual increases in expectations. Solar generation supports the standards directly.

Morrisons: Committed to net-zero British farming by 2030 (one of the most ambitious supermarket targets in the UK). The supplier programme cascades the target — farm suppliers are expected to be progressing toward operational net-zero by 2030, with on-farm renewables explicitly identified as a key lever.

Asda and Lidl: Both have supplier sustainability programmes, though less prescriptive than the Big Four. Both reference renewables-on-farm in supplier briefings without yet requiring formal disclosure.

CDP Supply Chain

CDP Supply Chain is the formal reporting framework that ties supermarket scope ambitions to supplier-level emissions data. Most major retailers participate in CDP Supply Chain and require their largest suppliers to submit annual CDP returns. The CDP framework explicitly asks suppliers to identify renewable energy installations including on-farm solar, with kWh generated, percentage of total energy demand, and trajectory targets.

For farm suppliers above the CDP submission threshold (varies by retailer — typically suppliers with >£10m annual sales to that retailer), CDP submission is non-discretionary. Solar generation evidence directly improves the CDP score.

EcoVadis and SBTi

Beyond CDP, several retailers also reference EcoVadis (third-party sustainability rating, common in commercial B2B) and SBTi (Science-Based Targets initiative — the gold-standard target-setting framework). On-farm solar contributes to both: EcoVadis explicitly references on-site renewables, and SBTi-aligned targets require reductions in Scope 1+2 emissions that solar directly supports.

What auditors actually look for

In a supplier audit (whether by the retailer’s own team or a third-party auditor like Bureau Veritas, NSF, SGS or Lloyds), the auditor typically asks for:

1. Documentary evidence of the solar install — invoice, commissioning certificate, MCS certificate, planning consent where relevant
2. Generation data — monitoring portal screenshots, annual kWh generated, monthly profile
3. Consumption data — half-hourly meter data showing on-site self-consumption
4. SEG export evidence — supplier statement showing kWh exported
5. Carbon factor reduction — calculation showing the percentage of total farm electricity consumption now from on-site renewables
6. Trajectory — plan to expand renewables across the holding over the next 3–5 years

We provide all of this as part of our handover documentation on every farm install — and we maintain access to monitoring portals through the system life for ongoing reporting support.

Contract retention impact

We’ve had multiple farm clients reference their solar install as material in supplier audit outcomes leading to contract retention, contract renewal on favourable terms, or in one case successful inclusion in a tier-1 retailer’s premium supplier programme that previously excluded the farm. The dollar impact varies hugely — for a major fresh produce supplier with seven-figure contract revenue, solar’s contribution to contract retention is among the highest-return investments the business has ever made.

What to document on your install

If your farm supplies a major UK retailer, make sure your install documentation includes:

1. Annual generation forecast (PVSyst output)
2. Self-consumption forecast (kWh used on-farm vs kWh exported)
3. Carbon-factor calculation showing Scope 2 reduction
4. Plan for any future expansion (additional buildings, battery, EV charging)
5. Trajectory toward 100% on-site renewable electricity (where achievable)

We provide all of this in every supplier-audit-ready handover pack. The investment in documentation is small compared to the value of being able to evidence Scope 2 reductions in a supplier audit when contract renewal is on the table.

What about CSRD?

The EU’s Corporate Sustainability Reporting Directive (CSRD) extends to large UK businesses with EU operations and indirectly to their UK supply chains. For most working farms it’s a future consideration rather than current obligation, but suppliers to large UK manufacturers selling into the EU should expect CSRD-driven Scope 3 disclosure asks from their customers over the next 2–3 years.

If you’re a UK farm supplying a major retailer or food manufacturer, the supplier audit landscape will keep tightening through the late 2020s. On-farm solar is one of the most material steps you can take to position the business for ongoing contract retention.