ScoreMyDataCenter Independent observatory

Understanding data centers

For the local official getting the developer's call, the resident discovering a public-inquiry notice, the journalist new to the beat: the essentials, without jargon. What hides behind the numbers.

This guide is written from the French regulatory and market context — the observatory's first scored country. The questions in block 3 travel anywhere; figures, rights and timelines are France-specific. Country-specific versions will follow the observatory's expansion.

What is a data center? France

A data center is an industrial building full of servers — the computers that run websites, videos, online services and, increasingly, artificial intelligence. These machines run day and night, draw electricity continuously and give off heat that must be removed. That is where their energy needs come from — and, depending on the cooling technique, their water needs.

To size a data center, the right unit is not the building's footprint but its electrical power, in megawatts (MW) — the flow of electricity the site can draw at any moment.

Three very different sizes share the same name:

“Classic” data center a few MW The vast majority of France's ~300 sites, connected to the distribution grid like a large factory<sup><a href='#src-what-1'>1</a></sup>
Large project 100 to 200 MW The electricity consumption of cities like Le Mans or Saint-Étienne<sup><a href='#src-what-1'>1</a></sup>
Mega-project above 400 MW About a dozen “out of the ordinary” projects in France; the Fouju AI Campus targets 1,400 MW on about 90 hectares<sup><a href='#src-what-1'>1</a></sup><sup><a href='#src-what-3'>3</a></sup>
a few MW classic data center 150 MW large project ≈ Le Mans 1,400 MW mega-project (Fouju)
Areas are proportional to electrical power.

Today, data centers account for about 2% of the electricity consumed in France; RTE expects about 4% by 2035<sup><a href='#src-what-1'>1</a></sup>. Worldwide, they used about 1.5% of electricity in 2024<sup><a href='#src-what-4'>4</a></sup>.

Takeaway — The same word covers a room of a few megawatts and a campus a thousand times more powerful. Facing a project, the first question is always: how many megawatts?

Sources: 1. RTE, “Data centers in key figures”, 2026 · 2. Journal du Grand Paris, 2025 · 3. Campus IA public consultation · 4. IEA, Energy and AI, 2025

Why it concerns my municipality France

A data center does not just occupy a plot: it settles into the municipality's networks — water, electricity, roads — and into its budget. Five concrete points.

Electricity. Recent large projects request 100 to 200 MW, the equivalent of the electricity consumption of cities like Le Mans or Saint-Étienne1. That power flows through the local grid: substations, lines, works.

Water. Some cooling techniques use very little water, others a lot: Amazon's data centers withdrew about 9.5 billion liters worldwide in 2025, the first annual figure the company has published2. The law takes the matter seriously: since May 2026, a building permit can be refused in France over “structural tensions on the water resource” (law no. 2026-403 of May 26, 2026, art. 35)3.

Noise. Cooling runs day and night, and backup generators are tested regularly. Permitted levels are set by the site's authorizations — they are written down, so they can be checked. What is regulated is not a distance but how much the noise rises at the neighbour's: how a project's noise is assessed, and how far away is far enough.

Land and jobs. A mega-project can occupy dozens of hectares — about 90 for the Fouju AI Campus4. For a comparable footprint, a logistics platform typically employs 300 to 400 people, a data center around 15 to 205.

Tax revenue. The site pays local taxes (property tax and the local business levy, among others), split between the municipality, the inter-municipal body and other authorities — with possible exemptions in the first years6. Hence the question to ask: what revenue, for whom, starting when?

Takeaway — None of these impacts is good or bad in itself: it all depends on the project, the place, and what is written in the filing. That is exactly what the next blocks teach you to read.

Sources: 1. RTE, “Data centers in key figures”, 2026 · 2. Data Center Dynamics, 2026 (AWS water) · 3. Gossement Avocats, law no. 2026-403, art. 35 · 4. Campus IA public consultation · 5. AFP / Connaissance des énergies, June 2026 (jobs) · 6. service-public.fr (CFE, exemptions)

What makes a “good” project?

There is no “good operator” or “bad operator” to be guessed from reputation. There are project choices, which can be read in the filing — or whose absence is telling. Here are six, and where to check them.

Announce early. The project is presented publicly before the permit is filed, not discovered on a notice board. Where to check: the date of the first public communication against the filing date.

Put water commitments in writing. The cooling technique and annual consumption are in the permitting documents, not only in the brochure. Where to check: the permitting file, available from the local authority.

Put heat recovery under contract. The difference lies between a paper study and a signed contract with a heat network, a swimming pool, greenhouses. Where to check: ask whether a contract exists, and with whom.

Pick the land that costs the territory least. Brownfield or already-artificialized land rather than farmland or natural areas. Where to check: the nature of the land, in the impact study.

Commit to publishing operating data. Electricity and water consumption, measured efficiency. Where to check: what the permitting documents promise to make public, and how often.

Negotiate written local benefits. Agreements, funds, facilities: what is signed binds; what is mentioned in a meeting does not.

In France — The law backs two of these levers: operators must study reusing the heat produced (energy code, art. L.236-2, from the law of April 30, 2025) and file a performance declaration for data centers (energy code, art. L.236-1)1.

Takeaway — A “good” project is not a project without impacts: it is a project whose impacts are written, quantified and verifiable. Our grid scores exactly that: what the project chooses, not only what it endures.

Sources: 1. Gossement Avocats, 2026 (energy code, art. L.236-1 and L.236-2; law no. 2025-391 of April 30, 2025)

Rights and timeline France

A data center does not get one authorization but several: a building permit and, most often, an environmental authorization — the French ICPE regime, which governs industrial installations1. Each has its calendar, and each opens rights to the public.

Before filing: the public consultation. A prior consultation, sometimes with a guarantor appointed by the CNDP (France's national commission for public debate), may be held upstream. Note: since a decree of March 3, 2026, data centers are no longer among the projects requiring mandatory CNDP referral2 — whether a consultation happens now depends on the developer or the State. When it does happen, it is the moment the project can still change the most.

During review: the public inquiry. For projects subject to environmental assessment it lasts at least 30 days (environment code, art. L.123-9)3. Anyone — resident of the municipality or not — can file written observations, at the town hall or online. They join the file and the inquiry commissioner responds to them in the report.

A special case since May 2026. A data center can be designated by decree a “project of major national interest”: the permit is then processed by the préfet, not the mayor. Even then, the permit can be refused over “structural tensions on the water resource” (law no. 2026-403 of May 26, 2026, art. 35)1.

After authorization: appeals. Deadlines are short, and they cannot be recovered: two months against a building permit from the first day it is posted on site, two months as well for third parties against an environmental authorization, counted from the last formality completed — posting at the town hall or publication on the prefecture's website (art. R. 181-50)4. A court appeal must also be notified to the author of the decision and to its beneficiary within fifteen days, or it is inadmissible (art. R. 181-51).

Once the site is running: the claim. Past the deadlines the authorization is final — but its PRESCRIPTIONS are not. Anyone affected can file a claim with the préfet, from the moment the site enters service, contesting the “insufficiency or inadequacy of the prescriptions”: noise from the chillers, generator tests, discharges, water abstraction. The préfet has two months to answer with reasons, silence counts as refusal, and where the claim is well founded he sets additional prescriptions (art. R. 181-52)5. It is the only lever left when the nuisance is discovered in use — and the most overlooked.

The buyer's trap. Anyone who buys or rents near a classified installation AFTER its authorization has been posted can no longer contest that authorization: the law rules them inadmissible (art. L. 514-6, III of the environment code)6. Before signing near an industrial zone, it is worth asking the town hall and the prefecture which authorizations are already posted there. The claim about prescriptions, however, stays open.

Takeaway — The calendar is everything: the same question asked during the consultation can change the project; asked after authorization, it changes nothing. Hence the point of arriving early — with the block-3 checklist.

Sources: 1. Gossement Avocats, law no. 2026-403, 2026 · 2. Actu-Environnement, decree of March 3, 2026 (CNDP) · 3. Environment code, art. L.123-9 · 4. Environment code, art. R. 181-50 — third-party appeal window, two months (decree no. 2024-423 of 10 May 2024) · 5. Environment code, art. R. 181-52 — claim to the préfet from entry into service · 6. Environment code, art. L. 514-6, III — third parties settling after the posting are inadmissible

Practical questions

« Are any data centers being built near me? »

We publish a grade for every known site and project, with its sources. Search for your town on the map or browse the ranking: a project's page says what is known about its power, its water, its land and its surroundings — and what is not. A project missing from our data is not a project that does not exist: it has not been made public yet, or we have not seen it yet.

« Why are people against data centers? »

Rarely on principle. What recurs in the files and in local campaigns comes down to four concrete things: electricity drawn from an already constrained grid, cooling water in areas that lack it, land sealed for a building that employs few people, and continuous noise for the closest neighbours. Added to that is a sense of asymmetry: the resource is local, the value leaves. That is exactly what the grade measures, pillar by pillar — see nuisances for what is lived from the street.

« Why do city councils approve data centers? »

Because a data center brings local tax revenue, construction work, and sometimes a heat network or fibre. Employment, once the site is built, is low — it is a building full of machines, not a factory. So the real question is not “for or against” but what the community gets in exchange, and what it writes into the authorization: commitments that are not written down cannot be enforced.

« What should we ask when a data center wants to come to town? »

Three figures first, in writing: power in megawatts, planned water consumption and the cooling method, and the distance to the nearest dwellings. Then three commitments: heat recovery, the filing calendar, and what will be published once the site is running. The block-3 checklist fits on one page, and Rights and timeline says when each question can still carry weight.

« A public-inquiry notice just appeared near my home. »

Note the end date: the inquiry lasts at least 30 days (see Rights and timeline). You can file a written observation, at the town hall or online, even if you do not live in the municipality. A precise, factual observation carries more weight than a petition of principle: lean on the block-3 checklist.

« I am a local official; a firm just called me about a project. »

Nothing obliges you to react on the spot. Ask for the file in writing, with three figures: power in megawatts, planned water consumption, filing calendar. The block-3 checklist fits on one page — bring it to the meeting.

« The project is already authorized. Is it too late? »

To attack the authorization itself, yes, past two months (see Rights and timeline). But a final authorization does not freeze its prescriptions: from the moment the site enters service, anyone can file a claim with the préfet contesting their insufficiency — noise, discharges, water abstraction — and the préfet must answer with reasons within two months (art. R. 181-52). Also left: asking for a monitoring body, and for regular publication of the operating data promised in the filing.

« Whom to contact, concretely? »

The town hall or inter-municipal body for planning; the prefecture for the environmental authorization file; the inquiry commissioner during the public inquiry; and the groups already active near you (see Going further).

« How do I know what already exists around me? »

Public maps list existing sites and projects — see Going further.

« Where can I consult a project's data? »

Every data-center page shows the score, and each indicator links to its public source (open data from RTE, INSEE, environmental-authority opinions, court decisions…): all of it is re-checkable. Official documents are mirrored by an archived copy so they stay reachable over time; press articles are linked, never reproduced. Neither the score nor its justification is ever behind a paywall.

Going further

To dig deeper, open and free resources — the same ones we use.

Maps and inventories

  • DCWatch (Hubblo) — digital common for data centre footprints (PUE, WUE, CUE, land, water), downloadable ODbL data — map: datacenters.hubblo.org
  • Le nuage était sous nos pieds — participatory map of sites, projects and mobilizations in France, maintained by a Marseille collective
  • Data Center Watch — tracking of project opposition in the United States

Reference figures

Understanding your rights

And to compare projects with each other: our map, our ranking and the full method — that is what this site is for.