UsesLevel 3 of 6 useUse, level 3 of 6Used to calculate 25 entries, levels 3 to 5Calculated with 4 entries, levels 1 and 2Database structure 
6Territories
5Organisations
4Occupations and activities
2Machine operations
1Calculation factorsWrite an email
An email of 150 words written by an assistant, from an instruction and the message received. Projet Celsius estimate.
- "Write, with reasoning" accounts for 65% of emissions in this scenario.
- 28% of the calculation rests on database assumptions; it does not measure actual use.
- Out of scope: server manufacturing, model training, the network and the user's device.
Sentence to citeWrite an email, Projet Celsius estimate: 0.11 gCO2e per email, for 0.23 Wh of electricity, servers worldwide (458 gCO2e/kWh).
Breakdown of emissions by item
0.11 gCO2e in total: 0.23 Wh of electricity × 458 gCO2e/kWh (servers worldwide).
Inputs of the calculation
PUE of the data centre, Read 1,000 tokens, Write, with reasoning
Comparison with the other uses
↓ The heaviest use in the topic, "Deep research": 45 gCO2e, 430 times more
Emissions of one use, linear scale, 7 of the 21 uses in the topic. For calculated values, servers worldwide.
Characteristics
| Unit | 1 email |
|---|---|
| Default location | world, 458 gCO2e/kWh (Ember 2025, life cycle); 11 other locations to choose from |
| Counted | the model reading and writing tokens, and data centre cooling |
| Not counted | server manufacturing, model training, the network and the user's device |
| Status | estimated |
All the characteristics
| Identifier | IA-0202, projetcelsius.com/en/ai/database/IA-0202/ |
|---|---|
| Version | 0.1 of 2 November 2026 |
| Category | Uses, a request to AI |
| 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
For a carbon footprint
| Item | purchases of services (GHG Protocol scope 3, category 1); regulatory BEGES, category 4 |
|---|---|
| Quantity | 1 email |
| Factor | 0.11 gCO2e per email, IA-0202 version 0.1, according to the grid at the location (location-based), servers worldwide |
| Total | 0.11 gCO2e · not counted: server manufacturing, model training, the network and the user's device |
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, with reasoning (without reasoning) | × 0.157 | 0.96 Wh | 0.15 Wh | 65 % | convention |
| Read 1,000 tokens | × 0.184 | 0.32 Wh | 0.059 Wh | 25 % | assumption |
| PUE of the data centre | × 1.10 on the rest | 0.021 Wh | 9 % | convention |
Entries that use it (25)
Handle a customer request, Write meeting minutes, Autonomous agent, 1 month, Process automation, Office worker, 1 year, Accountant, 1 year, Human resources, 1 year, Executive assistant, 1 year, Manager or executive, 1 year, Communications officer, 1 year, Journalist, 1 year, Consultant, 1 year, Lawyer, 1 year, Researcher, 1 year, Developer, 1 year, Data scientist, 1 year, Graphic designer, 1 year, Videographer, 1 year, Customer service officer, 1 year, Salesperson, 1 year, Field-based occupation, 1 year, Teacher, 1 year, Free personal use, 1 year, Microsoft 365 Copilot, 1 year, ChatGPT Business, 1 year 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.
Uses and assumptions
These publications shed light on AI tasks and uses. They do not measure the carbon footprint of the case calculated.
EnronSent
Role and limits : EnronSent
Author. Will Styler
What the publication covers. 96,106 messages sent by Enron employees, 13,810,266 words
What it does not cover. the messages received
Reading by the database. Professional emails from 2000 and 2001: an order of magnitude, not a norm
Write an email → : Write, with reasoning →
The email written, 150 words
Scope of the figure used. server, excluding the data centre
Limit. The quantity and the share entrusted to AI are database assumptions, not a measured footprint.
Write an email → : Read 1,000 tokens →
Length convention: an email
Scope of the figure used. A typical email: the sent messages of the Enron corpus average about 144 words; figure read in an excerpt, notice not verified
Limit. This publication supports the quantity of text or content processed, not its carbon footprint.
Write an email → : Write, with reasoning →
Length convention: an email
Scope of the figure used. A typical email: the sent messages of the Enron corpus average about 144 words; figure read in an excerpt, notice not verified
Limit. This publication supports the quantity of text or content processed, not its carbon footprint.
Energy and factors
The references of the selected values and of the entries used in this calculation.
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 read, medium model, large operator, at the server before PUE (Watershed table 2, public data as of June 2026)
Limit. A default value that Watershed derives from Google's measurement (0.24 Wh for the median text query of the Gemini app), with about 500 tokens per query and a written token costing 3 times a read token; Watershed does not give the split between read and written tokens. The 0.24 Wh already include the overhead of Google's data centre (0.02 Wh, 8%): with 375 tokens read and 125 written, the simplest reading, the factor contains it, and the PUE of 1.10 applied afterwards counts it a second time (about 9%). Values proposed for review, final at the next version of the framework
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
Write an email → : Data centre PUE →
The data centre, convention C3
Scope of the figure used. building cooling and losses
Limit. This figure covers part of the calculation; it does not measure the whole entry.
Reference of the selected value
Scope of the figure used. Default factor for a large operator, from the server to the data centre; 1.56 for an unknown operator
Limit. A default value, not a measurement
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 72 %
- Projet Celsius assumptions 28 %
Calculation assumptions
Quantities, nature and source of each assumption
Read 1,000 tokens : × 0.184
The instruction and the message being answered
Write, with reasoning : × 0.157
The email written, 150 words
Methodology conventions
With their alternatives
| The data centre | Server electricity is multiplied by 1.10 for the data centre |
|---|---|
| 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.
- 31 October 2026Creation of the database, in its first version (0.1).
