Yesterday, GHG Protocol announced that it’s combining forces with ISO on a single, harmonized corporate carbon accounting standard. If you’ve been half-watching the GHGP/ISO relationship over the past year, the broad direction isn’t a surprise. What’s new is how concrete it just got, and one piece of the announcement (a “multi-statement” reporting model) deserves some attention. Let’s deep dive on the GHG Protocol ISO consolidation.

The headline: one consolidated standard

ISO and GHGP will collaborate to consolidate the GHG Protocol’s Corporate Standard (2004), Scope 2 Guidance (2015), Scope 3 Standard (2011), and the Actions and Market Instruments (AMI) workstream with ISO’s 14064-1 into a single, co-branded standard. A joint public consultation is planned for Q2 2027. Importantly, the targeted publication timeline is Q4 2028, which is also when we expect all other changes to the standards to take effect.

That’s a meaningful commitment. GHGP had its own solo consultation draft for a high-level corporate standard due this quarter. That’s now been shelved in favor of the joint draft. GHGP is giving up its independent path to get to one standard.

Scope 2: Results are in, but no consensus yet

Alongside the merger news, GHGP published results from its Scope 2 public consultation, which ran from October 2025 through the end of January 2026 and drew nearly 1,100 responses from 56 countries. 

The consultation addressed proposed changes that would tighten how companies can claim clean electricity purchases, requiring hourly matching between consumption and contracts, as well as stricter rules on the geographical boundaries for clean energy procurement. Two theories of change were identified on how to drive impact:

• Precision drives impact: Hourly matching and stricter geographic rules direct capital towards new generation where and when it is needed most.
• Participation drives impact: Annual matching with a broad geographic boundary ensures the voluntary market is accessible and promotes more capital flowing to clean energy.

Support for hourly matching was notably low amongst companies and industries. GHGP’s governing board has asked the working group to refine its approach and resolve open-ended questions. There is broad agreement that accuracy and integrity matter in electricity emissions accounting, but no consensus yet on whether this approach gets there.

That unresolved tension is exactly what the multi-statement model is trying to address.

The “multi-statement” approach to reporting

Rather than picking a side in the location-based versus market-based debate, GHGP’s AMI proposal has companies report three distinct components:

1. Physical emissions. What’s actually happening in your operations and value chain, the real, location-based reality of grid mix and energy use. 

2. Market-based emissions. The existing certificate- and contract-adjusted figure companies already report today, reflecting RECs, PPAs, and other market instruments.

3. GHG impact statement. A new layer built on consequential accounting methods. Instead of asking, “What did you buy,” it asks, “Did your specific action (a new PPA, an investment in generation capacity) cause additional real-world decarbonization, or did it just reshuffle existing green supply among buyers?”

Public feedback on this approach during the AMI request-for-information period was reportedly strong, and it’s easy to see why: it’s a genuine compromise. The camp that wanted market-based accounting scrapped entirely doesn’t get that. The camp that relies on RECs for existing sustainability claims doesn’t lose that reporting line either. Everyone has to show more of their work.

Why this is a bigger deal than it looks

A few secondary effects worth noting:

• Reporting burden goes up. Companies (and the consultants supporting them) will effectively maintain three parallel emissions ledgers for Scope 2 instead of one. That means more data infrastructure, more methodology decisions, and more explaining to boards and stakeholders.
• It rewards additionality. The impact statement is structured to favor companies funding genuinely new clean generation over those buying cheaper, unbundled RECs from existing plants. Only the former shows up as a real consequential impact. Expect this to gradually reshape how corporate PPAs and REC purchases get structured.
• This is a preview of where disclosure regimes may land. CSRD, California’s SB 253/261, and the ISSB’s IFRS S2 all lean heavily on GHGP methodology already. A three-statement structure that starts as a voluntary reporting nuance has a path to becoming the reference point those frameworks eventually point to.
• This is still a proposal, not a final rule. It has to move through GHGP’s Technical Working Group and Independent Standards Board before anything is locked in, and the underlying methodology for the GHG impact statement hasn’t been fully published yet.

Bottom line

There is change on the horizon. However, these accounting developments shouldn’t distract from most organizations’ short-term priorities: improving data quality, expanding data tracking, and executing on reductions. The harmonized accounting standards won’t take effect until Q4 2028 at the earliest, and we don’t yet have perfect clarity on what will make it into the final standards. The evolution of emissions accounting standards is certainly worth keeping an eye on, but most sustainability teams don’t need to take substantial action to rebuild their emissions tracking and accounting approaches just yet.

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