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Data Center Waste Heat: Three Conditions to Check Before You Believe It

TL;DR In Île-de-France, 5 out of 165 data centers are connected to a district heating network, according to the FNCCR. Three gaps explain this: a data center operates for 15 to 20 years while a heating network is designed to last more than 30; beyond three to four kilometers, heat recovery becomes very complex; waste heat typically leaves the facility at 25 to 35°C, while district networks often require more than 60°C. Since June 2026, the Île-de-France Region has aimed to systematize heat recovery, and the Senate recommends a guarantee fund against the risk of site closure (per Localtis).

On June 25, 2026, the Île-de-France Regional Council adopted a siting strategy for data centers. Among its goals: systematizing the recovery of their waste heat — the heat that servers continuously generate and that cooling systems currently release into the outside air.

Heat recovery is one of the arguments made in favor of these facilities: server heat could warm homes or greenhouses. The Fédération nationale des collectivités concédantes et régies (FNCCR) measures how far this has actually gone in Île-de-France: 5 data centers connected to a district heating network out of the 165 in the region.

This gap has measurable causes. A site’s lifespan, its distance from the network, and the temperature of the heat it produces can all be known before any commitment is signed. Together, they determine how much of that heat ever reaches a network.

5 Connections Out of 165

The figure comes from an FNCCR article updated on June 26, 2026, following its event on June 18.

Elsewhere, recovery projects exist, and their scale varies widely. In Denmark, Meta’s site in Odense supplies up to 100,000 MWh of heat per year to the municipal network, according to a Vertiv blog post corroborated by Meta. France Datacenter’s guide on circular economy cites Equinix’s PA10 site, where 80 kW of recovered heat warms 476 m² of greenhouses. The same guide reports a case — APL with Danfoss — where up to 80% of heat could be recoverable; this is a specific project, and the figure does not hold for the industry as a whole.

The low number of connections in Île-de-France stems from three parameters, which the FNCCR and other public sources quantify.

Lifespan, the First Gap to Measure

A Network Built for 30 Years, a Site Built for 15 to 20

A district heating network is designed to last more than 30 years. A data center, 15 to 20 years, according to the FNCCR. The network is therefore amortized over a period at least one and a half times longer than that of the heat source it would depend on.

This gap falls on whoever finances the network. If the site closes, changes operator, or scales back activity before the pipes and substations are paid off, the network loses its heat source and must find another one. None of the public sources reviewed put a figure on this risk.

The Guarantee Fund Recommended to the Senate

On September 16, 2026, the French Senate’s Committee on Regional Development and Sustainable Development unanimously adopted information report No. 949 on the environmental footprint of artificial intelligence. It sets out 16 recommendations.

According to Localtis, the media outlet of the Banque des Territoires, two of them concern waste heat directly. The first would create a guarantee fund to cover the risk of a data center closing. The second calls for the publication of the decree provided for under Article 28 of the Reen Act, which would make the reduced electricity tax rate (TICFE) conditional on efficiency criteria, water consumption, and waste heat recovery. Neither measure appears in the summary published by the Senate itself; both are reported by Localtis alone.

At this stage, the guarantee fund remains a parliamentary recommendation. None of the sources reviewed describes a scheme currently in force that would protect a network owner against the closure of its heat source. Absent such a mechanism, the lifespan gap remains the responsibility of whoever invests in the network.

The distance between the data center and the heating network

Distance is decided the moment a site is chosen, and never again after that. A data center built eight kilometers from the nearest district heating network will not move closer to it. This parameter is also the easiest to verify: it only takes mapping the proposed location against the route of the existing network and its planned extensions. The logic also runs the other way: a planned network can be routed to pass within a few kilometers of an already operating site, provided that site remains in service for the network’s full amortization period.

Beyond three to four kilometers, recovery becomes very complex.

Jean-Marc Boursier, of the Institut national de l’économie circulaire (INEC), in an interview published in France Datacenter’s December 2025 guide.

Public recommendations point in the same direction. Still according to Localtis, the Senate report proposes prioritizing locations near housing, brownfield sites, and mixed-use buildings. France Datacenter’s guide also gives priority to brownfield sites, in line with the zero-net-land-take objective. A brownfield site in a business park far from any demand for heat would meet the second criterion but not the first; the two must be checked separately.

Heat temperature VS what the network requires

Data center waste heat typically leaves the facility at 25 to 35°C, according to the FNCCR. District heating networks often require temperatures above 60°C. At that level, recovered heat cannot be injected as-is.

The cooling method changes this figure. With direct-to-chip liquid cooling, where a liquid circulates in contact with the processors, recovered heat typically sits between 40 and 60°C, according to a blog post from Vertiv, a cooling equipment manufacturer. The gap with network requirements narrows without disappearing.

To close it, Vertiv writes that heat pumps “play an important role”: they raise the temperature to the level the network requires, consuming electricity in the process. The public sources reviewed put a figure on neither this added energy cost nor the corresponding investment; both depend on each project.

Temperature also depends on timing. Based on figures from the FNCCR and Vertiv, a conventionally cooled site produces cooler waste heat than a site equipped with liquid cooling, and a building’s cooling technology can change with each hardware refresh. The temperature stated at the permitting stage holds for a given configuration, at a given point in time.

What the Public Framework Already Provides

The Île-de-France Strategy of June 25, 2026

Report CR 2026-039, adopted by the Île-de-France Region, targets three objectives: increasing the local benefits of data centers, systematizing the recovery of their waste heat, and having data centers cover all the electricity grid costs they generate, including reinforcements that are today partly shared through the grid usage tariff (TURPE). This last point would require a legislative change, according to Localtis.

For implementation, the report announces an “analysis and project qualification grid and/or methodological toolkit,” “fiscal incentives for regions hosting data centers,” and a Data Center Observatory led by the Institut Paris Region. The sources reviewed do not detail its content; the grid will show, once published, whether the three parameters described above are among the criteria used to qualify a project.

The German Example

In Germany, new data centers must reuse at least 10% of their energy starting in July 2026, according to the Vertiv blog post, an obligation confirmed by the law firm Gleiss Lutz. A draft amendment presented to the Council of Ministers on June 24, 2026 would ease the requirement’s terms, and the process is still underway.

ADEME Funding

The EcoIDEN call for projects by ADEME, financed through France 2030 and opened on July 20, 2026, funds in particular the energy and water efficiency of data infrastructure and the recovery of its waste heat. Applicants are companies, either alone or partnered with research organizations; public institutions and local authorities may take part without obligation. The minimum project cost is €2 million, reduced to €500,000 for certain non-economic projects. The first review round has already passed; the call remains open until December 9, 2027.

Three Checks Before Any Commitment

The three parameters can all be documented before a permit is issued or a heat supply agreement is signed. Each calls for a specific piece of evidence.

  1. Lifespan. The site’s declared operating horizon, compared against the amortization period of the network that would receive its heat. If the former is shorter, the closure risk remains to be covered; the guarantee fund recommended to the Senate is, at this stage, only a recommendation.
  2. Distance. The site’s location mapped against the route of the existing or planned district heating network. Beyond three to four kilometers, the view cited by France Datacenter holds recovery to be very complex.
  3. Temperature. The planned cooling method and the exit temperature of the recovered heat, compared against the inlet temperature the network requires. A gap generally calls for a heat pump, whose cost and energy consumption factor into the project’s overall balance.

A project that documents all three points can be assessed on the evidence. A project that documents none of them presents heat recovery as an intention.

FAQ

How many data centers in Île-de-France are connected to a district heating network?

5 out of 165, according to the FNCCR (article updated on June 26, 2026). The figure covers connections to a district heating network specifically, not other possible uses of waste heat, such as greenhouses or neighboring buildings.

Does liquid cooling alone make waste heat usable by a network?

It makes it hotter, typically between 40 and 60°C according to Vertiv, versus 25 to 35°C generally for existing facilities according to the FNCCR. Since networks often require more than 60°C, a heat pump is still generally needed to raise the temperature further.

Does a guarantee fund against data center closure already exist?

Not at this stage, based on the sources reviewed. It is a recommendation from Senate information report No. 949, adopted in committee on September 16, 2026, as reported by Localtis.

VOLTEKKO’s Think Hub publishes sourced analysis every month on data center siting in France. Next up: water and land. Read the Think Hub articles

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