What is the carbon footprint of a data centre?
And how much electricity and water does it use?

A data centre is a building full of computers, called servers, that store our data and run online services, from email to artificial intelligence (AI) assistants. Together, the world's data centres used 415 TWh (terawatt-hours, or billions of kilowatt-hours) of electricity in 2024, almost as much as the whole of France. The International Energy Agency (IEA) expects 945 TWh in 2030, slightly more than Japan uses today.

A single large data centre built for AI, rated at 100 megawatts (MW), uses as much electricity as 100,000 households. Its carbon footprint comes first from that electricity, and therefore from the country it is plugged into: on French electricity, the same data centre emits 11 times less greenhouse gas than on the world's average electricity. Water, server manufacturing and the building come on top, in much smaller proportions.

1How much electricity does a data centre use?

From 25,000 households to 2 million households

The size of a data centre is measured in megawatts: the electrical power it can draw from the grid at any given moment. According to the IEA, a conventional data centre is rated at 10 to 25 MW. A large data centre designed for AI exceeds 100 MW, which over a year is the electricity of 100,000 households. The largest one under construction in 2025 approaches 2,000 MW, 20 times more, and the largest project announced reaches 5,000 MW.

In France, most projects applying for a connection to the high-voltage grid are rated at 100 to 200 MW, which RTE, the French grid operator, compares to the electricity consumption of French cities such as Le Mans or Saint-Étienne. About ten projects exceed 400 MW.

Servers first, then cooling

In a modern data centre, servers take about 60% of the electricity, according to the IEA. Cooling takes 7% in the most efficient large data centres and more than 30% in corporate server rooms. On average worldwide in 2024, cooling and the rest of the building add about 40% to the electricity used by the machines.

Together, almost as much as France

Taken together, data centres accounted for 1.5% of the world's electricity in 2024, and their consumption has grown by about 12% a year since 2017, 4 times faster than that of the rest of the world. The 945 TWh for 2030 come from one IEA scenario; our analysis Will AI use as much electricity as Japan? (in French) (in French) shows what that figure covers and what the other projections say.

The breakdown by region is on the chart of data centre electricity (in French) (in French) in our hub: the United States uses 45%, China 25% and Europe 15%. The share taken by AI, and the footprint of a single question put to ChatGPT, are covered in our article on AI electricity consumption.

2Where does a data centre's carbon footprint come from?

Electricity, ahead of everything else

A data centre emits little on site: its diesel generators only run during a power cut. Most of its emissions come from the power plants that produce its electricity. The IEA puts the emissions linked to data centre electricity at 180 million tonnes of CO2 in 2024, 0.5% of the CO2 emitted worldwide from burning fuels. That is about two thirds of the CO2 emitted by France in a year: 264 million tonnes in 2024, according to the Global Carbon Budget.

Coal remains the leading source of electricity for the world's data centres, about 30% in 2024, ahead of renewables (27%), gas (26%) and nuclear (15%), according to the IEA. With the growth expected, their emissions would reach 320 million tonnes of CO2 in 2030, before falling slightly.

The same data centre, 11 times fewer emissions in France

A kilowatt-hour produced worldwide emitted an average of 458 grams of CO2e in 2025 (the "e", for equivalent, counts all greenhouse gases), according to Ember data, against 41 grams in France, where electricity comes mainly from nuclear power and dams. Running at full power all year, a 100 MW data centre would emit about 400,000 tonnes of CO2e on the world's average electricity, and 36,000 tonnes in France.

The country matters as much as the size: a 100 MW data centre connected to the US grid emits almost as much as a data centre 10 times larger located in France. These figures are ceilings, since a data centre rarely runs at full power.

Servers, the building, and the tech giants' figures

Manufacturing the servers also counts. For its AI machines, Google calculates that electricity accounts for about 70% of emissions over 6 years of service, with manufacturing making up most of the rest. The tech giants often publish a much lower figure, because they deduct the renewable electricity they buy under contract. For 2024, Meta reports 1,358 tonnes of CO2e for its electricity, and 5.97 million tonnes based on the grids it draws its power from. Our analysis Meta emits only 1,358 tonnes? (in French) (in French) explains the gap.

For a company, the data centres where it rents servers belong in its digital footprint: this is the first place where a data centre's footprint becomes its own. The scope 3 guide explains which category to report them in.

3How much water does a data centre use?

Water to cool the servers

Servers heat up, and many large data centres remove that heat by evaporating water, in cooling towers or in so-called adiabatic systems, like the evaporative coolers fitted to some buildings. According to the IEA, a 100 MW data centre in the United States uses an average of 2 million litres of water a day, as much as 6,500 households. More than 60% of that water is used off site, mainly to produce its electricity.

The amount depends heavily on the cooling technique and the climate. Air conditioning in corporate server rooms uses very little water; evaporative cooling, used in about half of the very largest data centres, uses much more.

Water for electricity, the largest share

Worldwide, the IEA estimates that data centres consumed 560 billion litres of water in 2023, and could consume 1,200 billion in 2030. About two thirds of that water goes into producing their electricity, a quarter into cooling the servers on site, and the rest into manufacturing chips: a data centre's water use therefore also depends on its electricity.

In France, the water of 100,000 people

In France, the data centres of the 23 operators monitored by Arcep, the French electronic communications regulator, withdrew or consumed 6.5 million cubic metres of water in 2024, up 8% in a year. That is the annual consumption of more than 100,000 people. This volume is mainly a problem where a data centre draws from an aquifer or a river that is already under pressure. The water behind a single question put to an AI is covered in our article on AI's water footprint.

4Why is AI making data centres bigger?

Servers built on graphics cards

AI runs on so-called accelerated servers, fitted with graphics cards, chips that perform billions of calculations at the same time. According to the IEA, they took 15% of data centre electricity in 2024. Their consumption would grow by 30% a year until 2030, against 9% for conventional servers: they would account for almost half of the increase.

Each generation of chips performs more calculations for the same electricity, but usage is growing even faster. Generated images, and above all generated videos, weigh heavily: see the footprint of a generated image and that of a video. A question put to ChatGPT uses less and less, but more and more of them are asked: see what a query uses compared with a Google search.

Larger data centres, investment almost doubled

Investment in data centres has almost doubled since 2022, reaching 500 billion dollars in 2024, according to the IEA. Data centres are growing with the models: 100 MW for a large AI data centre today, 2,000 MW for the largest one under construction. AI is estimated to have used between 100 and 174 TWh in 2025 according to published estimates, which our AI figures database (in French) (in French) brings together.

Growth concentrated in a few areas

This growth is concentrated. In Ireland, data centres already use about 20% of the country's metered electricity; in Virginia, in the United States, 25%, according to the IEA. That is where AI weighs on grids, prices and water, far more than in the footprint of any single user: a year of regular AI use comes to a few kilos of CO2e, as our article should you boycott AI? shows. The actions that matter are in how to reduce the impact of AI.

For the other consequences, energy, water, metals and chip manufacturing, see the environmental impact of AI and why AI is bad for the environment.

5How big a role do data centres play in France?

About 300 data centres, 1 to 2% of electricity

France has about 300 data centres in 2026, according to RTE. Most are connected to the distribution grid with a few megawatts; only 8 are connected directly to the high-voltage grid, for 800 MW in total. Data centres on dedicated sites used 4 to 5 TWh in 2024, about 1% of the country's electricity, according to RTE's Bilan prévisionnel 2025 (its long-term adequacy report); with corporate server rooms included, 5 to 10 TWh.

18 GW of projects, mostly around Paris and Lille

The projects have changed scale. In May 2026, RTE had reserved almost 18 GW (gigawatts, or 18,000 MW) for about 80 projects, against 5 GW at the end of 2024. The Île-de-France region accounts for about 7 GW, Hauts-de-France for 6 GW. At the Choose France 2026 summit, SoftBank announced €45 billion for 3 data centres in Hauts-de-France by 2031.

This capacity will not be used straight away: operators expect 10 to 15 years to reach 80% of the power requested. RTE projects between 21 and 32 TWh in 2035 for data centres on dedicated sites, 5 to 7 times the consumption of 2024; our chart (in French) (in French) shows the trajectories.

Low-carbon electricity, local strain

Plugging a data centre into French electricity rather than the world's average electricity cuts the emissions of its electricity by a factor of 11. Yet according to ADEME (the French Agency for Ecological Transition), about 53% of the digital services used by people in France are hosted in data centres abroad, and data centres account for 46% of the carbon footprint of French digital use. The arrival of new data centres is nonetheless straining local grids: in Île-de-France, the power requested by projects, 6.5 GW, is close to the average power drawn by the whole region.

The operators monitored by Arcep emitted 178,000 tonnes of greenhouse gases in 2024, 23% more than in 2023, with electricity among the lowest-carbon in Europe. For how these emissions are classified in a Bilan Carbone® (the French carbon accounting method), see our article on AI emissions in carbon accounting.

At Projet Celsius, we think the right question to ask about a data centre is less its size than the electricity that powers it and the use it serves. A data centre running on low-carbon electricity for useful purposes weighs little; the same data centre running on coal, filled with videos generated for nothing, weighs heavily. For a company, the first step is to know where its services and AI tools run: that is the subject of our article on AI in your company's Bilan Carbone®.

6Key takeaways

• A large data centre built for AI, rated at 100 MW, uses as much electricity as 100,000 households, according to the International Energy Agency.
• Its carbon footprint comes mainly from its electricity: the same data centre emits 11 times less greenhouse gas in France than on the world's average electricity.
• The world's data centres used 415 TWh in 2024 and could use 945 TWh in 2030, driven by AI servers.
• Their water goes first into producing their electricity; in France, the data centres monitored by Arcep use the water of more than 100,000 people.
• In France, RTE has reserved almost 18 GW for about 80 projects, mostly in Île-de-France and Hauts-de-France.

Further reading: digital pollution statistics, and which AI to choose for the lowest environmental impact.

Further resources

Frequently asked questions

1How much electricity does a data centre use?

It depends on its size. According to the International Energy Agency, a conventional data centre is rated at 10 to 25 MW, and a large data centre built for AI exceeds 100 MW, which over a year is the electricity of 100,000 households. In France, most projects are rated at 100 to 200 MW, equivalent to French cities such as Le Mans or Saint-Étienne according to RTE. Together, the world's data centres used 415 TWh in 2024.

2How much water does it take to cool a data centre?

According to the International Energy Agency, a 100 MW data centre in the United States uses an average of 2 million litres of water a day, as much as 6,500 households, more than 60% of it off site, mainly to produce its electricity. The rest evaporates on site, in the cooling system. An air-cooled data centre uses much less water than one cooled by evaporation.

3What is the carbon footprint of the world's data centres?

The International Energy Agency puts the emissions linked to data centre electricity at 180 million tonnes of CO2 in 2024, about 0.5% of the CO2 emitted worldwide from burning fuels, and two thirds of the CO2 France emits in a year. They would reach 320 million tonnes of CO2 in 2030. The manufacture of servers and buildings comes on top.

4How many data centres are there in France?

About 300 in 2026, according to RTE, the French grid operator, 8 of them connected directly to the high-voltage grid. Those on dedicated sites used 4 to 5 TWh in 2024, about 1% of French electricity. In May 2026, RTE had reserved almost 18 GW for about 80 projects, mostly in Île-de-France and Hauts-de-France.

5Does a data centre emit less in France?

Yes, as far as its electricity is concerned. A kilowatt-hour produced in France emitted 41 grams of CO2e in 2025, against a world average of 458 grams, according to Ember data: the same data centre therefore emits about 11 times less. The manufacture of its servers, however, does not depend on the country where they run.

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