Renewable Energy and Carbon Accounting: RECs, PPAs and Green Tariffs

Renewable energy is one of the fastest and most cost-effective ways to reduce corporate Scope 2 emissions. Yet many organizations struggle to understand how to accurately account for it - and which renewable instruments actually deliver measurable carbon reductions.

The market for renewable energy certificates has exploded in the past five years. Corporate Power Purchase Agreements now represent billions of dollars in annual investment. Green electricity tariffs are proliferating across Europe and beyond. But without proper carbon accounting, companies risk overstating their renewable energy benefits or failing to capture legitimate emissions reductions.

This guide explains how to account for renewable energy across your Scope 2 emissions using the frameworks that matter: the GHG Protocol, BRSR, CSRD, and SECR.

Understanding Scope 2: Market-Based vs Location-Based Accounting

Scope 2 emissions arise from purchased electricity, steam, heating, and cooling. But how you calculate them - and what you subtract - depends on your chosen methodology.

The Two Approaches Under GHG Protocol

The GHG Protocol Scope 2 Guidance (2015) introduced two calculation methods:

Location-based accounting uses the average emissions intensity of the regional or national grid where you consume electricity. This reflects the actual environmental impact of your local grid mix - coal, gas, wind, solar, nuclear - regardless of your purchasing choices. Location-based figures are required by BRSR, CSRD, and SECR.

Market-based accounting uses actual emissions data from your chosen electricity supplier or the residual grid mix after renewable instruments are removed. This method reflects the carbon footprint of the energy you specifically purchased. Market-based figures are required by BRSR and CSRD as your primary disclosure; location-based is supplementary.

The critical difference: if you buy renewable energy certificates (RECs, REGOs, or Guarantees of Origin), your market-based Scope 2 can drop dramatically. Your location-based figure stays the same - because the grid mix hasn't changed.

Why This Matters for Compliance

Scope 2 emissions explains in detail, but the key point is that CSRD and BRSR require market-based reporting as your primary metric. This means your renewable energy purchases directly lower your disclosed Scope 2. SECR (UK) also requires market-based adjustments where you hold renewable instruments.

Location-based reporting, by contrast, is a "transparency" metric - it shows stakeholders the true grid decarbonization progress, independent of corporate purchasing decisions.

Renewable Energy Certificates: How They Work and What They Prove

A Renewable Energy Certificate (REC) is a tradable instrument that represents proof that one megawatt-hour (MWh) of renewable electricity was generated and fed into the grid.

Types of Certificates Across Markets

RECs in North America - issued by generators of wind, solar, and biomass. One REC = 1 MWh of renewable generation. RECs are retired (cancelled) once claimed by a buyer to prevent double-counting.

REGOs in the UK - Renewable Energy Guarantees of Origin issued by Ofgem-accredited generators. Functionally identical to RECs but UK-specific.

Guarantees of Origin (GOs) in the EU - issued under the Renewable Energy Directive (2018/2001). GOs must be registered in a central database and are supported by actual electricity transfer contracts or grid delivery.

Each certificate comes with metadata: generation date, fuel type (wind, solar, hydro), location, and generator ID. This transparency is why RECs, REGOs, and GOs are the backbone of credible market-based Scope 2 accounting.

What RECs Prove - and What They Don't

A REC proves that renewable electricity was generated. It does NOT prove:

• That the electricity reached your building (grid electricity is fungible - it's all mixed together).
• That the generator was built because you bought the certificate (additionality).
• That the certificate wasn't already embedded in your utility's default green tariff.

When you buy a REC and retire it, you're claiming the environmental attribute of that MWh. You're not claiming the physical electrons arrived at your site.

The Additionality Problem

The strongest criticism of RECs is that many are not additional - meaning the renewable generator would have been built anyway, even without your purchase. This is why GHG Protocol emphasizes that market-based accounting with RECs/GOs is preferable to location-based only for companies buying high-quality, additional renewable energy.

Look for RECs that meet:

• Gold Standard certification (global).
• Wind and solar from recent builds (last 5 years ideally).
• Geographic and temporal matching (certificate issued same month as consumption).

How to Account for Renewable Energy: Market-Based Scope 2

Power Purchase Agreements: The Real Decarbonization Tool

While RECs and green tariffs are certificate-based, a Power Purchase Agreement (PPA) is a long-term contract between a corporate buyer and a renewable energy generator.

Corporate PPAs (Physical)

A corporate PPA typically:

• Locks in a fixed price for renewable electricity (often 10-20 years).
• Specifies a generator (wind farm or solar facility).
• Includes physical delivery of electrons, though not necessarily to your exact location.
• Provides strong additionality proof - the generator was often financed based on the PPA commitment.

For carbon accounting, a corporate PPA with a dedicated renewable generator can reduce your market-based Scope 2 by the MWh you contract. If you buy 10,000 MWh annually under PPA and consume 12,000 MWh total, your claimed renewable portion is 83%, and your Scope 2 drops accordingly.

Virtual PPAs

A Virtual PPA (also called a synthetic PPA or financial PPA) is a contract for differences between a fixed strike price and a floating market price. No physical electricity changes hands - it's purely financial. Virtual PPAs hedge price risk but don't reduce your Scope 2 unless bundled with physical RECs or GOs.

How PPAs Cut Scope 2 Near Zero

Companies with large PPA portfolios matching their annual consumption can achieve near-zero market-based Scope 2. Microsoft, Google, and Amazon have signed 40+ GW of renewable PPAs. When accounted properly:

• Scope 2 (market-based) becomes the residual grid mix for unmatched consumption.
• Scope 2 (location-based) remains unchanged - it reflects actual grid decarbonization.

This is compliant with BRSR, CSRD, and SECR, provided you disclose both figures and your renewable instruments are clearly documented.

Green Electricity Tariffs: What Qualifies for Carbon Claims

A green tariff is a retail electricity product sold by utilities or suppliers offering renewable-backed electricity at a premium price.

What Actually Qualifies

To claim Scope 2 reductions via a green tariff:

• The tariff must be backed by physical renewable generation (hydro, wind, solar, biomass).
• It must be tracked via GOs (EU), REGOs (UK), or RECs (North America).
• Each MWh claimed must have a retired certificate attached.
• The tariff cannot be the supplier's default grid mix (to avoid double-counting).

Supplier Claims and Additionality

Many "green tariffs" are greenwashing - they use renewable generation that would have been built anyway, or they apply no additional premiums to renewable development.

Red flags:

• 100% renewable claims without certificate backing.
• Tariffs with no price premium over standard electricity.
• Suppliers that don't publish certificate serial numbers or retirement evidence.
• Tariffs claiming additionality without third-party verification.

BRSR and CSRD require transparent disclosure of the source and vintage of renewable energy claims. Greenio's platform automatically validates certificate metadata and tracks retirement, so you can defend your claims under audit.

On-Site Solar and Battery Storage: Direct Emissions Reductions

Unlike purchased renewable energy (which uses certificates), on-site solar directly reduces your Scope 1 and 2 emissions.

How to Account for On-Site Solar

If you install solar on your roof:

• Scope 1 savings: None - solar generation is not Scope 1.
• Scope 2 savings (market-based): Reduce your purchased electricity by the amount generated.
• Scope 2 savings (location-based): Same reduction - you consumed less grid electricity.

Example: Your annual consumption is 100 MWh. On-site solar generates 15 MWh. Your reported Scope 2 is now 85 MWh (location-based and market-based, unless you also buy RECs for the remaining 85 MWh).

Battery Storage Considerations

Battery storage complicates accounting slightly:

• If you charge during peak renewable generation hours, you reduce your Scope 2.
• If you discharge during peak grid demand (high-carbon hours), you're shifting emissions, not eliminating them.
• BRSR and CSRD require disclosure of battery charging patterns for accurate Scope 2 reporting.

On-site solar with battery storage is one of the few approaches that reduces both location-based and market-based Scope 2 simultaneously - making it especially valuable for organizations aiming for net-zero pathways.

GHG Protocol Scope 2 Guidance: Residual Mix vs Specific Supplier

The GHG Protocol allows two market-based sub-approaches:

Specific Supplier Approach

Use actual emissions data from your electricity supplier. If your supplier publishes a residual mix (grid electricity after renewable instruments are allocated), use that figure for unmatched consumption. This is most accurate and is the default for BRSR and CSRD.

Residual Mix Approach

If your supplier doesn't publish data, use the national or regional residual grid mix. This is less precise but compliant.

Both require documented renewable instruments (RECs, GOs, PPAs) with serial numbers, retirement dates, and fuel types. Greenio tracks all of this automatically, generating audit-ready evidence for BRSR, CSRD, and SECR disclosures.

FAQ

What is the difference between a REC and a carbon credit?

A REC (Renewable Energy Certificate) represents proof that one MWh of renewable electricity was generated. A carbon credit represents one tonne of CO2 equivalent avoided or removed. RECs are specific to electricity; carbon credits apply to any emissions source. RECs are used to reduce Scope 2 emissions via market-based accounting. Carbon credits are typically used to offset Scope 1 and 2 emissions under voluntary standards (Gold Standard, VCS). Under BRSR, CSRD, and SECR, you cannot count the same MWh as both a REC claim and a carbon credit.

Does buying a green energy tariff reduce my Scope 2 to zero?

No. A green tariff reduces your Scope 2 by the percentage of renewable energy you purchase, not to zero. If your tariff is 80% renewable-backed, your market-based Scope 2 drops 80%. The remaining 20% reflects the residual grid mix. Your location-based Scope 2 remains unchanged because it reflects your actual regional grid decarbonization, independent of your purchasing decisions. To reach near-zero Scope 2, you'd need 100% renewable PPAs or tariffs covering all consumption.

What is a corporate PPA and how does it work?

A corporate Power Purchase Agreement is a long-term contract (typically 10-20 years) between your organization and a renewable energy generator (wind farm, solar facility). You agree to buy a fixed volume of electricity at a fixed price. The generator gains certainty to finance the project; you gain stable pricing and strong additionality proof for your carbon claims. For carbon accounting, each MWh purchased under PPA reduces your market-based Scope 2 by one unit, regardless of physical delivery location (grid electricity is fungible).

How do I account for on-site solar in my carbon reporting?

On-site solar reduces your purchased electricity and therefore your Scope 2 emissions. Measure the annual MWh generated by your solar system (your installer should provide this). Subtract that from your annual grid electricity consumption. Report the net figure as your Scope 2 (both location-based and market-based). If you also buy RECs or PPAs for the remaining consumption, you can claim additional Scope 2 reductions on top. Ensure you have metering data and generation certificates from your solar provider to defend your claims under audit.

When do I need to report both location-based and market-based Scope 2?

BRSR, CSRD, and SECR all require you to report market-based Scope 2 as your primary metric. Location-based reporting is supplementary - it shows true grid decarbonization progress. SECR (UK) requires both if you claim any renewable instruments. Best practice is to disclose both annually, with clear methodology notes explaining your renewable energy sources, certificate serial numbers, and retirement evidence.

Conclusion

Renewable energy is the fastest route to Scope 2 decarbonization - but only if you account for it correctly. RECs, PPAs, and green tariffs each have different carbon accounting implications. The choice between market-based and location-based reporting is not optional under BRSR, CSRD, and SECR - it's mandated. And your renewable instruments must be documented, verified, and traceable.

Start by mapping your current electricity consumption and grid emissions intensity. Then layer on renewable instruments - whether RECs, PPAs, or tariffs - and track their retirement in a compliant carbon accounting system. Greenio automates this process, ensuring your renewable energy claims survive regulatory audit and stakeholder scrutiny.