Scope 2 Methodology Shift: Why the Market-Based Number Is About to Matter More

01The Setup

Scope 2 emissions accounting uses two methods: location-based (grid average emissions intensity in the region where electricity is consumed) and market-based (emissions reflecting contractual instruments like RECs, GOs, and PPAs). The market-based method has dominated corporate reporting because it allows companies to claim renewable energy procurement against their footprint.

Critics of the current market-based methodology have argued for years that it permits credibility-thin claims: annual matching (your annual REC quantity offsets your annual MWh consumption, regardless of when the renewable energy was produced versus when you consumed it), generic RECs from any geography, and no requirement for additionality (whether your purchase enabled new renewable capacity to be built).

The GHG Protocol's 2026 update addresses these criticisms with proposed tightening on three dimensions: temporal matching (hourly rather than annual), geographic matching (grid-region rather than continental), and additionality signals (preference for instruments that demonstrate impact on capacity additions).

02The Data

Companies relying on the cheapest tier of unbundled annual RECs satisfy current methodology easily — sometimes for as little as $0.50/MWh of claimed reductions. Under proposed guidance, that same claim becomes much harder to defend without supplemental hourly-matched procurement.

Estimates of the cost differential for hourly-matched PPAs vary by region and structure, but the consensus range puts the premium at roughly 15-40% above standard annual PPAs. That premium is shrinking as more developers can deliver hourly-matched supply, but it's still a step-change in cost-per-MWh of credible scope-2 reductions.

Timing: stakeholder review through Q3 2026; final guidance expected late 2026 or Q1 2027. Implementation phasing — how quickly companies need to align — is still being negotiated, but the direction of travel is settled.

03The Implication

Companies whose RE100 or Net Zero commitments rely on cheap, annually-matched, geographically-loose RECs will face a credibility cliff when the updated guidance lands. Some will be able to update without much change to underlying procurement — already-additional PPAs may already qualify or be close. Others will face material increases in the cost-per-MWh of credible scope-2 reductions.

Sustainability advisors will need to manage client expectations on roadmaps that were costed under the current methodology. A 2024 net-zero plan that assumed $1/MWh for credible scope-2 may be costed at $5-10/MWh under updated guidance — that's not a rounding error in the budget.

04The Recommendation

1. For corporates with RE100 commitments. Audit your current strategy against the proposed rules. If your reductions rely on annually-matched, generic RECs, build the case for upgrading to hourly-matched, additional procurement — and be prepared to defend the strategy publicly even if the rules technically permit the older approach for longer.
2. For sustainability advisors. Prepare clients for higher cost-per-MWh of credible scope-2 reductions. Update roadmaps and budgets accordingly — the conversation gets harder the longer you delay it.
3. For procurement teams. Evaluate hourly-matched PPA structures even at premium pricing. The pricing differential is shrinking as more developers can deliver hourly-matched supply; first-movers locked in early may pay less than late-movers facing a tighter market.
4. For boards and audit committees. This is a methodology shift, not a reporting catastrophe — but it is a real change in what credible reporting looks like. Plan the messaging now, not after the guidance finalizes.

The market-based methodology was an attempt to create accountability for corporate renewable energy procurement. The 2026 update is an attempt to make that accountability mean what it was supposed to mean from the start. For the companies that were already doing the work, it's validation. For the companies that found the cheap path through the accounting, it's a reckoning.