One Point Three

The number is PUE, Power Usage Effectiveness, and it is the simplest way to understand how efficiently a data centre uses electricity. A PUE of 1.0 means every watt drawn from the grid goes to computing. Anything above 1.0 is overhead: cooling, lighting, power distribution losses. The lower the number, the better.[1]

Google's planned data centre in Bissen has a PUE of 1.3. Google's own fleet-wide average is 1.10. The European average is 1.15. The Bissen project, in other words, would be the least efficient data centre Google operates, by a margin that is not small.[2]

Green MP Joelle Welfring raised the figure in parliament on Thursday morning, alongside two other concerns: electricity consumption and waste heat. The Bissen facility would draw approximately 1'000 gigawatt hours per year. That is roughly 15% of Luxembourg's total electricity consumption. It is more than every household in the country combined. The electricity will come from renewable sources, but there is no obligation to produce any of it in Luxembourg.[3]

Economy Minister Lex Delles, from the Democratic Party, framed the debate in strategic terms. Data centres are a matter of sovereignty, he said, for both Luxembourg and Europe. He acknowledged that the authorisation procedure dates to 2020 and that technical advances have occurred since. He spoke of strengthening the electricity grid, including the 380 kV interconnection to Germany. He agreed that waste heat should be recovered where possible, though he noted that Luxembourg has no national framework for this yet and that the infrastructure is not always easy to implement.[4]

The waste heat figure is striking. The heat generated by the data centre could provide heating for up to 10'000 households. In a country where energy costs remain a political issue, this is not a marginal detail. Welfring urged more innovation, arguing that recovering waste heat could improve public acceptance of the project. Delles responded that the government wants the heat recycled but "not at all costs."[5]

Outside parliament, the ecological movement Mouveco has filed a formal appeal against the project. Their objections go further than Welfring's. They argue that Google has not committed to implementing the best available technology, that key data on energy consumption and the cooling system have been withheld from public scrutiny on the grounds of trade secrecy, and that the planned use of diesel generators rather than sustainable battery storage is unacceptable. They are calling for the entire procedure to be cancelled. If they succeed, Google could be forced to revise the project comprehensively or face long delays.[6]

The Google project in Bissen has been controversial since the company acquired the 33-hectare site in 2017. An earlier legal challenge by Meco, another environmental group, was dismissed by the court in March 2022. The public consultation on the environmental impact closed on Friday, bringing the debate to a head.[7]

There is a broader context. Google's global electricity consumption has doubled in recent years, driven by the AI boom. The company has made its chip strategy greener, with the Ironwood TPU announced for 2025 being nearly 30 times more energy-efficient than the first TPU of 2018. But efficiency per chip does not solve the absolute growth in demand. A data centre that consumes as much as a small country's households will strain any grid, no matter how renewable the source.[8]

The question Delles posed in parliament is the right one, even if his answer was cautious. It is not whether Luxembourg wants data centres. It is under what conditions they can be sustainably integrated into the national energy system. A PUE of 1.3 in a country whose entire electricity supply is smaller than the facility's demand is not a detail. It is the difference between a project that serves the country and one that consumes it.[9]