Methodology for Calculating SSS-Inclusive and SSS-Excluded Supplier Emission Factors

Introduction

This methodology provides a detailed, step-by-step framework for calculating two distinct supplier-specific emission factors (SSEFs) in the context of Scope 2 market-based greenhouse gas (GHG) accounting, as outlined in the Greenhouse Gas Protocol (GHG Protocol). These factors are designed to support accurate and transparent reporting for users of the Granular Registry SSS Reporting platform, enabling compliance with evolving Scope 2 Guidance while addressing Standard Supply Service (SSS) attributes.

The two factors are:

  • SSS-Inclusive Supplier Emission Factor: This represents the GHG intensity (kg CO₂e/MWh) of electricity delivered by a supplier, incorporating the benefits of SSS carbon-free electricity (CFE) attributes (e.g., from RPS compliance, regulated nuclear, or hydro). It is suitable for reporters opting out of explicit SSS CFE claims, providing an implicit, diluted credit for SSS in the overall mix.

  • SSS-Excluded Supplier Emission Factor: This represents a "fossil-heavier" GHG intensity after subtracting SSS CFE attributes, concentrating emissions on the non-SSS portion. It is applied to unmet load for reporters making explicit pro-rata SSS CFE claims, ensuring no double-counting of clean attributes.

These calculations align with the GHG Protocol's proposed 2025 Scope 2 revisions (as of September 17, 2025, still in public consultation phase, with finalization expected mid-2026). They draw from key concepts such as the claim hierarchy (prioritizing supplier allocation), order of operations (SSS first, then voluntary, then residuals), and Scope 2 Quality Criteria (e.g., no double-claiming, exclusive retirement of energy attribute certificates [EACs]). The methodology supports both annual and hourly accounting, using credible third-party data sources (e.g., EEI Supplier Mix, Ember Grid Mix, EPA eGRID) and proxies when direct data is unavailable.

Assumptions:

  • Calculations are performed per supplier or energy-market region (e.g., U.S. ISO, EU Member State), treating the supplier as a proxy "market" if regional data is incomplete.

  • CFE is treated as zero-emission (0 kg CO₂e/MWh), including CH₄ and N₂O where applicable.

  • Excludes non-SSS resources (e.g., green tariffs, competitive tenders) per SSS exclusions.

  • Units: kg CO₂e/MWh; includes CO₂, CH₄, N₂O per local protocols.

Data Requirements and Hierarchy

To ensure accuracy and feasibility, follow this data hierarchy:

  1. Supplier-Attested Data (Preferred): Direct from the supplier (e.g., attestations, IRPs, or fuel mix disclosures) for generation, load, SSS CFE, and EAC retirements.

  2. Regulatory Filings: RPS/CES compliance reports, utility annual reports, or certificate-tracking systems (e.g., PJM GATS, AIB GO cancellations).

  3. Third-Party Proxies: Public datasets like EEI Carbon Emissions & Mix, Ember Grid Mix CFE % by Technology, or EPA eGRID for baselines and breakdowns.

  4. Bottom-Up Reconstruction: If none available, rebuild from plant-level data (e.g., EPA Form 923, EU ETS) with high uncertainty flags.

Key Inputs:

  • Supplier total retail sales/load (MWh) from EIA Form 861 (U.S.), Eurostat (EU), etc.

  • SSS CFE MWh: From compliance REC retirements, public hydro/nuclear allocations, or proxies (e.g., grid CFE % × SSS share by technology).

  • Fossil/non-SSS MWh and fuel-specific intensities (e.g., from eGRID or national PRTRs).

  • For Hourly: Load/generation profiles (e.g., PG&E spreadsheets, EIA Hourly Grid Monitor).

Calculation of SSS-Inclusive Supplier Emission Factor

This factor reflects the supplier's delivered electricity intensity, including SSS CFE benefits (e.g., lower EF due to embedded RPS-renewable energy sources). It is used for opt-outs, providing indirect SSS credit without explicit claiming.

Step-by-Step Process

  1. Gather Baseline Mix Data:

    • Obtain supplier's total generation mix: SSS CFE MWh + Fossil/Non-SSS MWh + Other (e.g., imports).

    • Calculate total emissions: Sum (Fossil MWh × Fuel-Specific Intensity) for all non-CFE portions. Use supplier-attested or third-party data (e.g., EEI for U.S. utilities).

  2. Incorporate SSS CFE:

    • SSS CFE is included as 0 kg CO₂e/MWh. No subtraction—treat as part of the full mix.

    • Verify SSS eligibility: Confirm via decision trees (e.g., regulated cost recovery, non-bypassable charges) and exclusions (e.g., no cross-border public ownership without funding ties).

  3. Compute the Factor:

    • Formula: SSS-Inclusive EF = Total Emissions (tCO₂e) / Total Supplier Load (MWh).

    • Example: Supplier load = 100,000 MWh; SSS CFE = 25,000 MWh (0 emissions); Fossil = 75,000 MWh at 0.533 kg/MWh average intensity.

      • Total Emissions = 75,000 × 0.533 = 40,000 tCO₂e.

      • SSS-Inclusive EF = 40,000 / 100,000 = 0.4 kg CO₂e/MWh.

  4. Hourly Variant (Optional):

    • Use profiles: H_SSS-Inclusive EF = H_Emissions / H_Load, incorporating temporal SSS CFE (e.g., hydro in off-peak hours).

    • Proxy if needed: Apportion annual SSS CFE using technology curves (e.g., NREL solar profiles).

  5. Validation:

    • Ensure no double-counting: Confirm EACs are retired for SSS only (not voluntary).

    • Cross-check: Compare to published SSEFs (e.g., Climate Registry) or grid averages.

Calculation of SSS-Excluded Supplier Emission Factor

This factor excludes SSS CFE, creating a higher-emission "residual" for explicit claimants' unmet load. It concentrates emissions on non-SSS resources, ensuring exclusive SSS credit.

Step-by-Step Process

  1. Gather Baseline Mix Data:

    • Same as SSS-Inclusive Supplier Emission Factor, Step 1.

  2. Quantify and Subtract SSS CFE:

    • Calculate SSS CFE MWh using pro-rata proxy if needed: (Grid CFE % by Technology × SSS Share) × Supplier Load.

    • Subtract allocated SSS CFE (across claimants) from the clean mix portion.

    • Residual Load = Total Load - SSS CFE MWh.

  3. Compute the Factor:

    • Formula: SSS-Excluded EF = Total Emissions (tCO₂e) / Residual Load (MWh).

    • Emissions remain unchanged (all from fossil/non-SSS).

    • Example (continuing from above): Residual Load = 100,000 - 25,000 = 75,000 MWh.

      • SSS-Excluded EF = 40,000 / 75,000 ≈ 0.533 kg CO₂e/MWh.

  4. Hourly Variant (Optional):

    • H_SSS-Excluded EF = H_Emissions / (H_Load - H_SSS CFE).

    • Use time-stamped data or proxies (e.g., assume flat nuclear, variable renewables).

  5. Validation:

    • Prevent shuffling: Unclaimed SSS remains ineligible for others.

    • Cross-check: Align with residuals (e.g., AIB Residual Mix for EU).

Application in SSS Reports

  • For Explicit Claimants: Claim SSS CFE (0 emissions) + voluntary + SSS-Excluded EF on remainder.

  • For Opt-Outs: Apply SSS-Inclusive EF to full load.

  • Outputs: Include both factors, breakdowns, uncertainties (e.g., ±10% for proxies), and disclosures (e.g., "SSS-Excluded assumes no cross-supplier leakage").

Limitations and Uncertainties

  • Data Gaps: Proxies may overestimate/underestimate (e.g., curtailment not accounted for); mitigate with sensitivity analysis.

  • Regional vs. Supplier: If partial coverage, flag potential deviations from full residuals.

  • Updates: Monitor 2026 final Guidance for refinements (e.g., stricter hourly mandates).

This methodology ensures robust, verifiable factors that promote alignment between compliance and voluntary efforts.

PreviousCalculating Verified SSS with Utility DataNextSSS Designation Decision Trees

Last updated

Was this helpful?