Brussels, Belgium

The first mandatory facility-level sustainability reporting regime for data centres anywhere, established under the recast EU Energy Efficiency Directive, with its first reporting cycle in 2024. Participation was 36% despite the requirement being mandatory. Ireland, one of Europe's densest data centre markets, reported at around 17%; Czechia reported nothing at all. The Green Web Foundation's analysis confirms there are no known consequences for non-reporting, which is the direct cause of low compliance. The 36% that did report produced three concrete findings that voluntary regimes had not surfaced: (1) the efficiency gap between the largest and smallest facilities was about 40%, narrower than the industry claim that small operators run at PUE above 2–3; (2) larger facilities had worse water use effectiveness, with a step change at the 500–1000 kW tier; (3) reported renewable shares of 85–96% rest on roughly 70% unbundled annual Guarantees of Origin, with only ~29% power purchase agreements and under 0.5% on-site generation. The design implication is narrow: attach a penalty to the reporting requirement.