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Does an AI prompt pollute more than an email?

All comparisons

A text prompt emits about 0.2 g of CO₂e; an average email about 0.3 g. The two are level. That is not what the best-known number says. The 19 g per email figure comes from a 2011 study by ADEME, France's environment agency, and it measures a one-megabyte send. Between the two numbers sit fifteen years of efficiency gains and two different accounting boundaries.

1 MB email with attachment (ADEME, 2011)19 g
AI text prompt (0.2 g)0.2 g
Verdict

The figure on the left is the most quoted number in the digital-footprint debate, and the least comparable. It dates from 2011, it covers a one-megabyte email, and it counts the hardware at both ends. Set against today's estimate for an average email, roughly 0.3 g, the 0.2 g text prompt is level with it.

Figures updated on June 30, 2026

Where does the 19 g per email figure come from?

From a 2011 study by ADEME, the French environment agency, on the environmental impact of electronic communication. It puts a one-megabyte email sent to a single recipient at 19 g of CO₂e. The number spread through the French press and is still quoted there. Two things make it a poor match for a prompt. It measures a heavy email, attachment included, not three lines dashed off in a hurry. And it describes the hardware of 2011: servers, networks and devices have since delivered the same service on far less energy.

What does an email actually cost today?

About 0.3 g of CO₂e for an average one, according to the 2020 edition of Mike Berners-Lee's “How Bad Are Bananas?”. The same author put a standard email at 4 g and one with a large attachment at 50 g in his 2010 edition. Over a decade he cut his own average by more than ten times, crediting more efficient devices and data centres. His 2020 range is still enormous: 0.03 g for spam stopped by a filter, up to 26 g for a marketing email sent to a hundred people and read by one. “An email” is not a unit of measurement.

What weighs more, the compute or the time at the screen?

The time at the screen, and here are the workings. A laptop draws roughly 25 Wh per hour of use (ADEME). Writing a prompt and reading the reply takes two minutes, so 25 × 2/60 = 0.83 Wh. Converted at the average grid carbon intensity this site uses, 480 g per kWh, that is 0.4 g of CO₂e. Twice what the query itself costs in the data centre. The same logic applies to an email at both ends, for the person writing and the person reading. These comparisons mostly measure human attention, not network traffic.

So which one emits more?

There is no clean answer, and that is the honest result. A text prompt sits between 0.15 g (operational compute only) and roughly 1 g (full life cycle, server manufacturing included). An email sits between 0.03 g and 26 g, depending on whether it is filtered spam or a barely-read marketing blast. The two ranges overlap completely. Separating them would mean fixing the same boundary, the same electricity grid and the same content on both sides. Nobody has done it, which is why the comparison gets quoted in both directions depending on who is quoting.

What is worth taking away?

That both sit at the same order of magnitude, and that it is a small one. Each is measured in tenths of a gram, against 170 g for a kilometre by car and 3 g for a kilometre by high-speed train. It takes roughly 850 prompts to match a single kilometre of driving. What shifts the scale is never the single action: it is the count. A billion prompts a day is no longer a tenth of a gram.

Related equivalents

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Frequently asked

Does an email pollute more than an AI prompt?+

Not decisively. An average email runs to about 0.3 g of CO₂e (Berners-Lee, 2020 edition) and a text prompt to about 0.2 g: the same order of magnitude. The widely quoted 19 g covers a one-megabyte email and comes from a 2011 ADEME study.

Why has the email figure fallen so far?+

Because devices and data centres now deliver the same service on far less energy than in 2010, and because early estimates loaded hardware manufacturing heavily. Mike Berners-Lee moved from 4 g per email in 2010 to about 0.3 g in 2020, on his own numbers. No equivalent revision has been published for ADEME's 19 g.

Is deleting old emails worth doing for the climate?+

The leverage is elsewhere. At 0.3 g each, you would need to delete more than 500 emails to save the equivalent of one kilometre of driving. Clearing an inbox is a symbolic act, not a climate one.

Pricing an action does not tell you whether to take it. A 0.2 g prompt that replaces an hour of manual work is not the same deal as one fired off out of habit. Weighing that up is a different trade: the GHIS studio works with small and mid-sized companies on how they use AI.

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