UsesconventionLevel 2 of 6 machine operationMachine operation, level 2 of 6Used to calculate 14 entries, level 3Calculated with 3 entries, levels 1 and 2Database structure 
6Territories
5Organisations
4Occupations and activities
3Uses
1Calculation factorsWrite 1,000 tokens, with reasoning effort
The tokens written by the model, multiplied by the chosen reasoning effort.
- "Write 1,000 tokens" accounts for 52% of emissions in this scenario.
- The calculation covers the writing of tokens by the model, reasoning draft included.
- Out of scope: reading the context and the data centre.
Sentence to citeWrite 1,000 tokens, with reasoning effort: 0.84 gCO2e per 1,000 tokens, for 1.8 Wh of electricity, servers worldwide (458 gCO2e/kWh).
- Calculated with
- Used to calculate
How the calculation is built
The draft of a reasoning model is written, not re-read. Tasks use it so that reasoning does not multiply the documents read.
Comparison with the other machine operations
Characteristics
| Unit | 1,000 tokens |
|---|---|
| Default location | world, 458 gCO2e/kWh (Ember 2025, life cycle); 11 other locations to choose from |
| Counted | the writing of tokens by the model, reasoning draft included |
| Not counted | reading the context and the data centre |
| Status | convention |
All the characteristics
| Identifier | IA-0021, projetcelsius.com/en/ai/database/IA-0021/ |
|---|---|
| Version | 0.1 of 2 November 2026 |
| Category | Machine operations, what the server computes |
| Choice of the selected value | database calculation from the entries this one is made of, at the quantities of the unit |
| Sources | calculation of the database |
| Licence | CC BY 4.0 |
Usage parameters
Advanced settings
Result for the chosen case
Breakdown by item
Quantity, unit value, contribution and nature of the data for each item
| Item | Quantity | Unit value | Contribution | Share | Nature of the data |
|---|---|---|---|---|---|
| Write 1,000 tokens | × 1 | 0.96 Wh | 0.96 Wh | 52 % | convention |
| Reasoning | × 1.92 on the rest | 0.88 Wh | 48 % | convention |
Entries that use it (14)
Conversation of 10 exchanges, Write an email, Write a page, Article of 1,000 words, Proofread a page, Translate a page, Query a PDF, Summarise 30 pages, Analyse a spreadsheet, Web search with an AI, Generate a function, Have code reviewed, Browser agent, Automated workflow and
Sources of the calculation
3 publications, for this entry and those used to calculate it, with the chosen parameters.
The result is calculated by Projet Celsius. The sources below support its uses, its factors and its conversion; they do not all measure this total.
Energy and factors
The references of the selected values and of the entries used in this calculation.
Role and limits : PEReN
Author. PEReN, published by Arcep
What the publication covers. GPU energy at inference, 22 open models, 6 question sets
What it does not cover. cooling, manufacturing, training
Reading by the database. Open models
Reference for the variant "With reasoning, medium effort"
Scope of the figure used. + 92% on average with reasoning, effect estimated by regression on 22 open models and 6 question sets; 95% interval from - 21% to + 348%
Limit. Open models, varied tasks
Watershed · Aug. 2026
Estimating GHG Emissions from AI Use: Framework for Corporate-Level Measurement ↗ (new tab)
Role and limits : Watershed
Author. Bistline, Ulissi, Davis, Glidden, Joyce, Li, Mohsenin and Suh (Watershed)
What the publication covers. factors per 1,000 tokens read and written at the server before PUE (host and standby machines included), PUE separate (1.10 for a large operator, 1.56 for an unknown operator)
What it does not cover. clean measurements, the model and the hardware
Reading by the database. Default factors proposed for review (public data as of June 2026); for a large operator, taken from Google's measurement published in 2025 (Elsworth et al.), which already contains the data centre overhead; constant per token, they underestimate long contexts and agents according to the authors
Reference for the variant "Medium model, Watershed default factor"
Scope of the figure used. Default factor for 1,000 tokens written, medium model, large operator, at the server before PUE (Watershed table 2, public data as of June 2026)
Limit. 3 times the reading factor, based on the ratio between writing and reading selected by Watershed (Patel et al., Splitwise, 2024). Same derivation and same caveat as for reading: Google's 0.24 Wh already include about 8% of data centre. Values proposed for review, final at the next version of the framework
Conversion into carbon
The source of the electricity factor of the selected location.
Worldwide: 458 gCO2e/kWh, life cycle.
Role and limits : Ember
Author. Ember, Our World in Data
What the publication covers. electricity generation over the life cycle, by country
What it does not cover. guarantees of origin
Reading by the database. The same source for all countries
Conversion of electricity into carbon: worldwide
Scope of the figure used. the production of electricity over the life cycle, including power plant construction and fuels
Limit. An average for the chosen country, not the electricity contract or the data centre of a specific service.
Nature of the data
Published readings, conventions, assumptions
- database conventions 100 %
Calculation assumptions
Quantities, nature and source of each assumption
Write 1,000 tokens : counted 1 times
1,000 tokens written
Methodology conventions
With their alternatives
| The default location | Without other information, the servers are in the world, at the world average electricity |
|---|---|
| Electricity, location-based, on a life cycle basis | The kilowatt-hour is that of the servers' country, on a life cycle basis, from a single source for all countries |
| Two significant figures | A calculated value is rounded to two significant figures, a published value is reproduced with the precision of its source; the calculation keeps full precision |
| The formula | the sum of what makes up the entry, then CO2e: electricity (Wh) multiplied by the carbon intensity of the server location (gCO2e/kWh), divided by 1,000 |
| Calculate a case without an entry | The formula, the default values and a step-by-step example |
History
Entry in version 0.1 of 2 November 2026, in the database in version 0.4
- 2 November 2026Version 0.1 of the entry, as of the date of its current value.
- 12 November 2026Default setting : without reasoning (0.44 gCO2e) becomes medium reasoning (0.84 gCO2e).The "with reasoning" entry was worth as much as the entry without reasoning, its effort being set to "none" by default. The tasks that use it keep their own setting: no other value changes.
- 31 October 2026Creation of the database, in its first version (0.1).
