Weight and energy

Under Media quality, Publish says what loading the course costs, as an everyday gesture: “At this setting, loading this course uses as much energy as an LED bulb lit for 25 minutes.” The sentence follows the setting you choose and the course’s real weight. It is not meant as an exact figure: it puts the orders of magnitude back where they belong.

How it is worked out

• The weight: what a learner loads to go through the whole course in their language, at the chosen quality. Media count as Elabora prepares them for that setting, with the narration and the player.
• The energy of a gigabyte: 0.03 kWh for the network (a fixed line and its router, or mobile), the data centre and the CDN. It is the latest French average (Arcep, 2024 data: 0.02 kWh over a fixed line, 0.14 over mobile). It was 0.08 kWh in 2020 (ADEME and Arcep) and 0.065 in 2022: it keeps going down, so this figure will stay a good approximation without being updated.
• The gesture: an 8 W LED bulb, the equivalent of the old 60 W bulb. 100 MB is 3 Wh, a bulb lit for 22 and a half minutes: Publish rounds it to 25 minutes.

Both sides of the comparison are electricity, so it holds in every country.

The learner’s computer or phone is not counted: it uses the same whatever the course weighs. Its share depends on the time spent on the course, and above all on its manufacture (see below).

Why the figures vary so much

Published values for a gigabyte range from under 0.01 to nearly 1 kWh. The gaps come mostly from three things.

• What is counted. A network uses nearly as much energy whether it carries little data or a lot: between 2015 and 2018, European operators’ consumption stayed flat while traffic tripled. What one more gigabyte really adds is therefore small, around 0.005 kWh over a fixed line. Dividing all the networks’ energy by all the traffic gives a higher average; Elabora uses that one.
• The network. A gigabyte over a mobile network costs 3 to 7 times more than over a fixed line: 0.14 kWh in France, if every learner took the course on mobile.
• The year. On fixed networks, the energy per gigabyte has halved about every two years since 2000. The very high figures that went round in 2019 came from worldwide averages of 2017, and one of them mixed up bytes and bits: it has been corrected since.

And carbon?

Carbon depends on the country’s electricity. The icon at the end of the sentence says it with a compact petrol car (170 g of CO₂ a kilometre, its manufacture included), for the country set on your computer. Countries fall into four broad bands, which move little from year to year:

Electricity, per kWh	Examples	Value counted	100 MB loaded
under 100 g of CO₂	France, Switzerland, Sweden, Norway	100 g	0.3 g, a car over 2 metres
100 to 300 g	Belgium, Spain, Canada, United Kingdom, Italy	300 g	0.9 g, 5 metres
300 to 500 g	Germany, United States, Japan, Côte d’Ivoire, world average	500 g	1.5 g, 9 metres
over 500 g	Morocco, Tunisia, Algeria, Senegal, Poland, China, India, Australia	700 g	2.1 g, 10 metres

Each band counts its upper value, by prudence. A country the table does not know takes the world average, and the icon says so. These figures count only the electricity the network uses: with the manufacture of its equipment, ADEME counts about 10 g of CO₂ a gigabyte in France (2020 data).

What matters more than weight

In France, making the devices and servers accounts for 60 % of the digital footprint, and networks for 4 % (ADEME and Arcep, 2022 data). A laptop kept one more year saves far more than every megabyte taken out of a course: making it weighs as much as loading a 100 MB course two hundred thousand times.

Weight is still a useful lever, above all for video and mobile. An hour of high-definition video weighs 2 to 3 GB, as much as twenty ordinary courses. A few simple habits:

• choose Lighter quality when the video does not need more: it often weighs two to three times less;
• keep video for what it shows better than a picture or a text;
• make courses short and useful: the time a learner spends in front of a screen counts more than megabytes.

Sources

• ADEME and Arcep, Évaluation de l’impact environnemental du numérique en France et analyse prospective, part 2, January 2022 (2020 data), and its 2025 update (2022 data).
• Arcep, Enquête annuelle « Pour un numérique soutenable », 2024 and 2026 editions.
• Arcom, Arcep and ADEME, Étude de l’impact environnemental des usages audiovisuels, October 2024.
• Carbon Trust, Carbon impact of video streaming, June 2021.
• G. Kamiya (International Energy Agency), The carbon footprint of streaming video: fact-checking the headlines, 2020.
• J. Aslan, K. Mayers, J. Koomey and C. France, “Electricity intensity of Internet data transmission”, Journal of Industrial Ecology, 2018.
• J. Lundén, J. Malmodin et al., “Electricity consumption and operational carbon emissions of European telecom network operators”, Sustainability, 2022.
• The Shift Project, Did The Shift Project really overestimate the carbon footprint of online video?, June 2020.
• Ember, yearly electricity data, April 2026 release (2025 data), as shown by Our World in Data.
• ADEME, impactco2.fr: “Go de données”, “Voiture compacte essence”.