ESG guide · Scope 2 emissions

Commercial solar for Scope 2 emissions reduction

A working guide to using commercial solar PV for Scope 2 emissions reduction, ESG reporting, and customer-side procurement requirements. How on-site solar compares to off-site renewable PPAs, what reporting frameworks recognise, and how to quantify the value.

The Scope 2 framing

Under the GHG Protocol — the standard for corporate emissions accounting — Scope 2 emissions are those from purchased electricity, heat, or steam. For most UK businesses, electricity dominates Scope 2. On-site solar PV reduces grid electricity consumption and therefore directly reduces Scope 2 emissions.

The reduction is quantifiable: solar generation in kWh × grid carbon emissions factor in kg CO₂/kWh = Scope 2 emissions reduction in tonnes CO₂. UK 2026 marginal grid emissions factor is approximately 0.18 kg CO₂/kWh and falling as the grid decarbonises further.

Why on-site solar beats off-site PPAs for ESG provenance

On-site solar provides the strongest possible ESG provenance for renewable electricity because generation and consumption are co-located — there's no chain-of-custody question. Off-site renewable arrangements (corporate PPAs, sleeved arrangements, REGOs) work for ESG reporting but require careful documentation:

  • On-site solar: Direct meter-measured generation, fully attributable to the operating site. Supports both location-based and market-based Scope 2 reporting. RE100 qualifying without additional certificate retirement.
  • Corporate PPAs (off-site): Contract-based arrangements with off-site renewable generators. Supports market-based Scope 2 only. Requires REGO retirement and contract documentation. Credible but more complex.
  • Renewable supplier tariffs: 100% renewable tariffs from the supplier. Supports market-based Scope 2 only. REGO-backed but less specific provenance than dedicated PPAs. Lowest cost route to market-based Scope 2 reduction.

For organisations facing customer-ESG procurement requirements, on-site solar is materially preferred over off-site routes. Customer audits increasingly verify on-site renewable deployment as the strongest provenance signal.

Reporting frameworks supported

TCFD (Task Force on Climate-related Financial Disclosures)

UK statutory disclosure requirement for listed companies and large LLPs since 2022. On-site solar supports the "transition planning" and "emissions metrics and targets" pillars. Annual generation and Scope 2 reduction figures audit-ready from monitoring data.

SECR (Streamlined Energy and Carbon Reporting)

UK statutory annual reporting requirement for large companies and LLPs. Reporting includes total UK energy use, GHG emissions (Scope 1 and 2), and at least one intensity metric. On-site solar reduces SECR-reportable Scope 2 emissions and total grid electricity use.

CDP Climate Disclosure

Voluntary global climate disclosure with strong investor and customer uptake. CDP scoring (D, C, B, A levels) directly affected by demonstrated emissions reduction. On-site solar deployment positively impacts CDP score through measurable Scope 2 reduction.

SBTi (Science Based Targets initiative)

Voluntary target-setting framework for emissions reduction aligned with climate science. SBTi-validated targets typically require Scope 1+2 reductions of 4.2% per year (well-below 2°C pathway) or 6.3% per year (1.5°C pathway). On-site solar contributes directly to targets.

RE100

Voluntary commitment to 100% renewable electricity. On-site solar counts directly toward the RE100 percentage. Major customers with RE100 commitments (Google, Microsoft, Apple, Adobe, BT, BSkyB, Sky, others) increasingly require supplier-side renewable deployment.

B Corp certification

Voluntary certification for businesses meeting verified social and environmental performance standards. B Corp scoring includes environmental performance metrics where on-site renewable deployment contributes positively.

Customer ESG procurement — sector-specific drivers

Customer-side procurement requirements vary by sector but increasingly drive supplier solar deployment:

  • Major UK retailers — Tesco Pathways, Sainsbury's 1.5°C-aligned engagement, M&S Plan A, Co-op Future of Food, Asda commitments. Cascade Scope 3 targets through supplier scoring.
  • Automotive OEMs — BMW, Mercedes, Volvo, Stellantis, Ford have all set supplier emissions targets. Tier-1 supplier ESG scoring directly affects supply terms.
  • Aerospace primes — BAE Systems, Rolls-Royce, Airbus all operate supplier sustainability requirements. ATI funding routes support supply-chain decarbonisation.
  • Pharmaceutical primes — GSK, AstraZeneca, Pfizer, Roche, Sanofi all run supplier engagement programmes with measurable Scope 2 reduction targets.
  • Major hospitality groups — InterContinental, Hilton, Marriott, Accor brand standards increasingly require franchise property-level Scope 2 reduction.
  • Government and public-sector procurement — UK Government Buying Standards, NHS Net Zero Supplier Roadmap, Local Authority procurement frameworks all increasingly require supplier emissions data.

Scope 2 reduction FAQs

How does on-site solar reduce Scope 2 emissions?
Scope 2 emissions are emissions from purchased electricity. On-site solar reduces grid electricity consumption, which directly reduces Scope 2 emissions by the carbon factor of the displaced grid electricity (UK 2026 marginal grid factor ~0.18 kg CO₂/kWh). A 250 kWp commercial solar system typically displaces 180–230 MWh of grid electricity per year, reducing Scope 2 emissions by 30–40 tonnes CO₂ annually.
What's the difference between location-based and market-based Scope 2?
Location-based Scope 2 uses the average grid emissions factor for the country where electricity is consumed. Market-based Scope 2 uses contract-specific emissions factors — Renewable Energy Certificates, supplier-specific emissions, or Power Purchase Agreement provenance. On-site solar reduces both location-based and market-based Scope 2; off-site renewable energy procurement (e.g. corporate PPAs) only reduces market-based.
How do customer ESG procurement requirements affect commercial solar economics?
Materially in some sectors. Manufacturers serving major retailers, automotive OEMs, or aerospace primes increasingly face supplier ESG scoring that influences procurement decisions. Solar deployment improves Scope 2 reporting and supplier scoring, sometimes supporting preferential supply terms or contract retention. The customer-ESG benefit is hard to quantify upfront but real on the ground.
Is on-site solar better than off-site renewable PPAs for ESG reporting?
On-site solar provides stronger ESG provenance because there's no chain-of-custody question — generation and consumption are co-located. Off-site renewable PPAs (corporate PPAs, sleeved arrangements) require careful documentation of energy provenance and certificate retirement to be credible. RE100 commitments increasingly favour on-site over off-site for primary location renewable deployment.
What ESG reporting frameworks does on-site solar support?
TCFD (Task Force on Climate-related Financial Disclosures), SECR (Streamlined Energy and Carbon Reporting — UK statutory), CDP Climate Disclosure (voluntary), GRI Standards (voluntary), SBTi (Science Based Targets initiative), B Corp certification. On-site solar PV supports all of these through measurable Scope 2 reduction. Reporting requires measurement-grade data (meter-monitored, not estimated) for inclusion in audited disclosures.
How do I quantify the ESG value of solar for our reporting?
Three reportable metrics from on-site solar: (a) annual generation in kWh from monitoring portal; (b) Scope 2 emissions reduction = generation × marginal grid emissions factor; (c) percentage of operational electricity from renewable sources. Annual figures audited against monitoring data are SECR/TCFD-credible. For RE100 reporting, the qualifying metric is "renewable energy as percentage of total electricity demand" — on-site solar contributes directly without certificate-retirement complexity.

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