World's largest particle accelerator begins warming thousands of local French residents with waste energy from the 16-mile Large Hadron Collider — CERN's accelerator leverages its massive cooling network to help slash local carbon emissions

The world’s largest particle accelerator now has an important new mission: heating thousands of homes. The Large Hadron Collider at CERN has begun to funnel the waste heat from its cooling system to a new residential and commercial area in the nearby French town of Ferney-Voltaire, with the new linkup expected to be able to heat several thousand homes at once.

This new network is one of several initiatives that CERN is introducing to help it move towards more “environmentally responsible” research and to help reduce CO2 emissions. The LHC, the jewel in CERN’s crown, is otherwise better known for its large-scale research around the building blocks of the universe, including the discovery of the Higgs boson particle in 2012.

Active since mid-January, the new setup has been made possible by the introduction of a new heat exchange system. The system draws the heat from the LHC’s cooling system, which stretches all around the 16-mile accelerator, and funnels it directly into Ferney-Voltaire’s new district heating network.

The heat, which would otherwise be an unused waste product, means that these homes don’t require an active heating system, such as gas or electric, which helps prevent thousands of tons of carbon dioxide emissions each year. As CERN itself explains, this is made possible by the LHC’s design, with eight “surface points” across its 16-mile range – the eighth passing particularly close to Ferney-Voltaire.

The equipment at point eight requires extensive water cooling. Rather than pass this through a cooling tower, with the energy then lost, the new setup instead pushes the hot water through two 5 MW heat exchanges, housed in a new building that links CERN’s exchange with the new Ferney-Voltaire heating system. However, CERN confirms that this 5 MW output could “theoretically” double when CERN is fully operational, as long as it doesn’t impact the LHC’s main research mission.

The residents of Ferney-Voltaire might have to wait a while before they can take full advantage of CERN’s waste heat, however. The Large Hadron Collider is expected to shut down as part of its Long Shutdown 3 process for several years of upgrades and maintenance from mid-2026. This will reduce CERN’s output to the new heating system to “between 1 and 5 MW,” excluding several months while the system isn’t operational. CERN has other plans to capture waste heat, including at its Prévessin data center, where it expects to use heat recovery to warm most of the on-site buildings from late 2026.

This isn’t the first project to reuse waste heat that we’ve seen, although it may be one of the largest in scale. For instance, a swimming pool in Redditch, England, has been funneling the waste heat generated by a nearby crematorium to heat its swimming pool since 2013. A more recent project, the Bunhill 2 Energy Centre, has captured waste heat from the London Underground train network to provide heat and hot water to over a thousand homes since 2020. Microsoft also announced a plan to use waste heat from a data center to warm residents in a Finnish town, and we’ve even seen a UK couple heat their home using a Raspberry Pi cluster.

CERN’s efforts are an ambitious way to capture waste energy for the wider benefit of the residents close to its headquarters. With so many data centers built in ultra-cold climates during this AI boom period, the LHC’s efforts could provide inspiration for future high-energy infrastructure – where there’s heat, there’s opportunity.

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