How indexation mechanisms and sleeve structures can undermine the GHG Protocol claim a corporate buyer thinks they have purchased — and what to negotiate into the contract to protect it.
A corporate buyer signs a Power Purchase Agreement for 30 GWh per year of renewable electricity. Their sustainability function reports a 30 GWh reduction in market-based Scope 2 emissions for the next financial year. The audit signs off. The annual report goes out.
Eighteen months later, the same audit team flags the position. Not for the volume — that part of the agreement is intact. For the certificate matching, the temporal alignment, or the sleeve structure used to settle the contract. The 30 GWh claim cannot be fully substantiated under the current GHG Protocol Scope 2 Guidance. The reported emissions reduction is restated. The auditor’s note now appears in the financial statements.
This pattern has occurred at major UK and European corporates over the past 18 months. It is not a marginal technical issue. It is a real reputational and reporting risk that sits inside contracts which were never structured with audit in mind.
The trap is rarely caused by a single defective clause. It is usually three structural features acting together.
First, mismatched temporality. The PPA delivers renewable electricity on an annualised basis — total volume across the year. The GHG Protocol’s most rigorous matching standard requires hourly alignment between consumption and generation. Most CPPAs do not deliver this and most corporates do not negotiate for it.
Second, certificate retirement timing. Renewable energy certificates (RECs, REGOs, GOs depending on geography) are the instrument that conveys the renewable attribute. The contract must specify when and where the certificates are retired, by whom, and in whose registry account. Vague language here is where the audit position fails.
Third, sleeve margin disclosure. Sleeved PPAs introduce a utility intermediary between the generator and the corporate buyer. The utility’s margin, the structure of the sleeve, and the basis on which the electricity is delivered all matter for the Scope 2 claim. Buyers frequently do not see, and do not ask to see, the relevant detail.
The Scope 2 claim is not a function of the renewable electricity bought. It is a function of how the contract is structured and how the certificates are handled. The two are routinely conflated.
The defensible position is reached through a small number of specific contract amendments. The first is a temporal matching clause that defines how generation and consumption will be aligned for reporting purposes — ideally hourly, at minimum monthly. The second is a certificate handling appendix that specifies registry, retirement timing, ownership transfer, and audit trail. The third, for sleeved structures, is a sleeve transparency clause that gives the buyer visibility of the underlying structure.
These are not exotic asks. They are increasingly standard in well-structured corporate PPAs. The buyers asking for them are the buyers whose Scope 2 claims will survive scrutiny in 2026 and beyond.
Arc’s PPA consultancy practice reviews proposed contracts on behalf of corporate buyers before signature. We review the specific clauses identified above, identify the contract risks that create future audit exposure, and negotiate amendments on the buyer’s behalf. We do not have a commercial relationship with any PPA counterparty, which is what allows us to do this work credibly.
If you are considering a corporate PPA, or have an existing PPA you are not certain will support your Scope 2 claim under audit, we would welcome a conversation.