Methodology
How the hub's data are selected, documented, checked and updated.
1.Choosing sources
The hub relies on public, dated and traceable sources: reports from institutions (IEA, ADEME, RTE, Arcep), scientific studies that are published or posted as preprints, company reports, open datasets (Ember, FAO, via Our World in Data). Each value is read in the document itself, to the page, before it enters the database.
The 3 statuses of a value
- Primary : read in the document of the body that produced it.
- Secondary : reported by the press or a third party. It enters the database only if the original can be found; otherwise it is explicitly attributed, with its caveat.
- Calculation : derived by us (a share, a sum, a conversion). It is flagged as such and redone at each update.
Each value is verified a second time, independently of the first reading, by reopening the source.
2.Defining scopes
Each data point is tied to an explicit scope: what is counted, what is not, the area, the year. Without it, 2 figures cannot be compared: for AI, 6 methodological choices make results vary by a factor of 1 to several thousand.
The 6 choices that make figures diverge
- Electricity according to the actual grid or according to green electricity contracts.
- Cooling water alone, or the water of electricity and manufacturing as well.
- Hardware manufacturing counted or not.
- Median or average value.
- Assumed utilisation rate of the servers.
- Uses that nobody publishes (image, video, agents).
The full analysis: Why do estimates of AI's impact differ?
3.Selecting a value
When sources diverge, the hub selects a reference value and shows the range, with the reason for the choice written in the entry. This value is held in the hub's database, which the charts, the hub's tools and the blog articles read; a gap between 2 pages is an error, which we correct and record in the changelog.
| Quantity | Selected value | Why |
|---|---|---|
| Electricity, world average | 458 gCO2e/kWh | Ember value for 2025, life cycle, the one used in the AI Impact Database (a single source for all countries); the country of the servers of the major assistants is not published |
| Electricity in France | 41.4 gCO2e/kWh | Same source as the world (Ember, life cycle); the ADEME Base Carbone, 51.9 g, remains the reference for carbon footprints in France |
| A text question | 0.3 Wh | Independent estimate by Epoch AI (February 2025), bounded by the 2 values published by providers |
| An image | 2.9 Wh | Average of the open models measured |
| A 5-second video | 90 Wh | The most downloaded open generator; range from 0.14 to 415 Wh |
Calculated values are rounded to 2 significant figures; published values are reproduced as the source gives them.
4.Documenting uncertainties
Each entry states the nature of the value (measurement, estimate, scenario, company declaration), its limitations and what it does not allow us to conclude. Scenarios are presented as scenarios, with their variants when the source publishes them. Declarations with no published methodology, such as the 0.34 Wh announced by OpenAI, are flagged as such.
5.Updating and correcting
Publications on the subject keep coming: each new source is read, and the value concerned reviewed. Each change of value is recorded in the history of its entry and in the public changelog, corrections included.
To report an error, write to us stating the page and the source: each report is checked, and the correction is dated.
6.Reusing and citing
The hub's charts, data and texts are under a CC BY 4.0 licence: free to reuse, including commercially, provided the source is cited. Each entry offers its citation and its data as CSV. The details: Cite and reuse.
Example of a data entry
- Indicator
- Electricity consumed by data centres in 2024
- Value
- 415 TWh
- Region
- World
- Year
- 2024
- Share of global electricity
- about 1.5%
- Source
- IEA, Energy and AI, April 2025
- Status
- Agency estimate
- What is excluded
- Users' devices (computers, phones); Telecommunication networks outside the data centres; Manufacturing of the equipment
To use a figure from the hub
- Check that its scope matches your question: it is written at the top of each entry.
- Cite the original source and the date, with the link to the entry.
- Keep the unit and the year: "415 TWh in 2024, all the world's data centres", not "415 TWh".
