Scope 2: location-based versus market-based, for AI workloads
Carbon figures for AI start with energy and then apply an emissions factor. Which factor you choose can change the answer more than any efficiency gain.
Two methods in one table
| Location-based | Market-based | |
|---|---|---|
| Emissions factor | Average emissions of the grid where the energy is used | Emissions of the generation the buyer has contracted for |
| What changes it | The local grid mix | Contracts and certificates the buyer holds |
| What it answers | What did our consumption cause on this grid, on average? | What did our purchasing choices claim? |
Dual reporting
Under the GHG Protocol's 2015 Scope 2 Guidance, companies operating in markets with supplier-specific data report Scope 2 both ways and label each result by its method; the two results are not added together (GHG Protocol Scope 2 Guidance (2015)). The GHG Protocol is revising its Scope 2 standard, so check its site for the current status.
Why AI carbon figures differ
- Different factors: the same kWh gives different emissions under each method.
- Different energy: chip, system and facility boundaries give different kWh before any factor is applied.
- Different scope: one 2025 study counted Scope 2 only and excluded training and embodied emissions (Jegham et al., 2025).
- Different timing: annual averages and hourly factors give different results for the same workload.
Where the ledger ends
The Joule Ledger measures energy: five accounts at a declared meter point. It does not set or choose an emissions factor. Report the energy first, then state the factor, its method and its year, so readers can recalculate.
A reporting pattern
- Energy by account and meter point, labeled Measured or Estimated.
- Location-based emissions, with the grid factor and its year.
- Market-based emissions, with the instruments used.
- Neither figure presented as neutral or zero.
Not legal or accounting advice
This guide is general information. Follow the current GHG Protocol text and any reporting rules that apply to you.
Questions
Which method should we publish?
Where dual reporting applies, both, each labeled. Publishing only the lower figure without saying so misleads.
Does JL-26 calculate emissions?
No. JL-26 measures energy. Emissions depend on factors chosen outside the method.
Sources
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Location-based and market-based Scope 2 methods, why AI carbon figures differ, and where an energy ledger ends and an emissions factor begins.