Earth Day has been celebrated on 22 April since 1970, and in 2025 its theme is “our power, our planet”. This reflects the increasing need to manage energy globally and CERN, for its part, is wholly committed to improving its energy performance. CERN was one of the first scientific laboratories to obtain ISO 50001 certification for energy management, in February 2023. ISO 50001 is the benchmark international standard for implementing systems and processes to continually improve energy performance. It entails setting up, monitoring and improving an energy management system, in line with CERN’s Energy Policy and the relevant legislation. Each year, a surveillance audit checks for compliance and continuous improvements. Following a successful audit in 2024, CERN has now passed the 2025 surveillance audit carried out by the French Association for Standardisation, AFNOR. The audit explored a range of topics across CERN, from cryogenics to cooling and ventilation, from human resources to health and safety. No nonconformities were identified, and many strengths were singled out. “The level of maturity of CERN’s energy management system was particularly highlighted in the 2025 audit,” explains CERN’s energy coordinator, Nicolas Bellegarde. “CERN was able to demonstrate improvements to energy performance through a large number of technical and organisational actions, as well as through the day-to-day operations of the various teams.” Each year, CERN strives to improve energy management by deploying a strategy based on three pillars: to keep the energy required for its activities to a minimum, to improve energy efficiency, and to recover waste energy. The 400 kV electrical substation on the CERN Prévessin site. (Image: CERN) A good example is the new data centre in Prévessin, which was inaugurated in 2024 and is designed to provide up to 12 megawatts of computing power, responding to the computing needs of CERN. A data centre’s energy efficiency is measured by its “power usage effectiveness” (PUE), with numbers closest to 1.0 being the most efficient. New data centres achieve PUEs of between 1.2 and 1.4. and large data centres typically average 1.5. But the Prévessin data centre is instead targeting 1.1. In addition, the new building is equipped with an efficient heat-recovery system that will contribute to heating all the buildings on the Prévessin site. Also in 2024, CERN signed three power purchase agreements (PPAs) with French energy providers so that the construction of the offsite solar power farms can begin and 140 GWh/year can be provided by renewable sources from 2027, corresponding to about 10% of CERN’s annual electricity consumption during accelerator operation years. Energy management is part of the Laboratory’s commitment to environmentally responsible research. Find out more here: home.cern/about/what-we-do/environmentally-responsible-research