UK data centre efficiency ranked by PUE

28 October 2025, updated 12 November 2025

If a petrol car was as efficient as a data centre, you could drive 3,000 km or more before needing to fuel up, like New York to Los Angeles, or London to Kyiv and back. And if you were were efficient as a data centre, maybe you could jump over it. ¹

Here’s a list of UK data centres, ranked by Power Usage Effectiveness (PUE) ²:

• 1.09 - Google 2024 global fleet average, trailing 12-month PUE. Excellent disclosures but Waltham Cross in the UK hasn’t been running for 12 months yet. European data centres are 1.06 - 1.1.
• 1.15 - Amazon Web Services 2024 global average, and best centre is 1.04 in Europe, but no detail on Bracknell, Didcot and Swindon.
• 1.16 - Microsoft 2024 global average, but no detail on UK South and Wales, Ireland is 1.18.
• 1.16 - Atos Longbridge - 2023 per this article, though in 2022 it was 1.12?. Atos fleet average is currently 1.44
• 1.18 - DataVita OCP-Ready facility, Scotland - “Ultra-efficient design with a PUE of 1.18”, however a different page mentions “industry-leading PUE of 1.17”
• 1.2 - DataVita DV1 and DV2, Scotland — “Design PUE of 1.2 […] Indirect adiabatic evaporative cooling”
• 1.26 - Vantage global average - 2023 ESG report
• 1.27 - Kao Data KLON-01, Harlow - ESG report 2024-5 and here. However Harlow sites “offer an SLA-backed PUE of 1.2”. Estate average is 1.53 but “By January 1, 2025 new data centres operating at full capacity in cool climates will meet an annual PUE target of 1.3”.
• 1.2-1.4 - Virtus - “Most new builds between 1.2 and 1.4”. Virtus doesn’t seem to publish PUEs but back in 2014 was hopeful of “achieving a design PUE below 1.2”
• 1.25 - public cloud industry average - IDC - US only? cited by Amazon here, but I’m not paying $7.5k for a 14-slide research deck
• 1.3 - Climate Neutral Data Centre Pact 2025 target - “By January 1, 2025, new data centres operating at full capacity in cool climates will meet an annual PUE target of 1.3 and 1.4 for new data centres running at full meeting capacity in warm climates. Existing data centres will achieve these same targets by January 1, 2030”
• 1.39 - Equinix (global average) — “global annualized average PUE of 1.39 in 2024” and 2024 annual report, which doesn’t have site-by-site PUE data but does have emissions data
• 1.41 - Colt - 2024 sustainability report: “global average PUE of 1.41”. And London 6-8 will target 1.35.
• About 1.4 - Ark Cody Park - eyeballing a graph in the 2023 sustainability report
• 1.49 - Kao Data KLON-05, Northolt - ESG report 2024-5
• About 1.5 - Ark Meridian Park - eyeballing a graph in the 2023 sustainability report
• 1.53 - Kao Data average
• About 1.55 - Ark Spring Park - eyeballing a graph in the 2023 sustainability report
• 1.58 - Digital Realty - “PUE rating of 1.58, well below the industry average of 1.8”. Digital Realty doesn’t seem to have published its own PUE numbers, but their 2024 Impact report talks about “Exceeded 5% improvement for North America colocation portfolio and 3% improvement for Europe portfolio”.
• 1.59 - Vodafone - “The trailing-twelve-month (‘TTM’) energy-weighted average PUE for all our owned and operated data centres was is 1.59 in (FY21: 1.64)”
• 1.63 - Kao Data KLON-02, Harlow - ESG report 2024-5
• 1.63 - on-premises enterprise average - IDC - US only? cited by Amazon here
• 1.64 (ish) - UK sector target 2022 - “The sector target has been agreed as a 4.539% reduction in PUE by 2022 from a 2018 baseline”, but the target reductions are smaller if you’re currently closer to a PUE of 1
• 1.66 - Global Switch - 2024 ESG report: existing estate across Europe (1.76, though their FRAN site is at 1.17 in 2024) and Asia Pacific (1.56). New data centres “target an annualised PUE of less than 1.2”.
• 1.74 - Kao Data KLON-06, Slough - ESG report 2024-5
• 1.8 - UK measured average 2017 - this figure is cited broadly and mentions a 2017 TechUK report: “the sector achieved this target as a whole, reducing PUE by just over 10% (from 1.959 to 1.797)” but nb that this was an average only for those colo providers who signed up to Climate Change Agreement targets in order to receive a discount in the Climate Change Levy.
• Unknown - NTT - one of the large data centre providers in UK. The 2024-25 ESG report doesn’t mention PUE (?!) but might set a record in mentioning tCO2e - 735 times! of the large data centre providers in UK. The ESG factset talks about reducing PUE but doesn’t say what their PUE actually is. Sigh.
• Unknown - Cyxtera/Brookfield - one of the large data centre providers in UK. No mention in parent company Brookfield’s 2024 sustainability report.

(If your data centre has a good PUE, let me know!)

Power usage effectiveness or power unit efficiency PUE) is a ratio that describes how efficiently a computer data center uses energy. You divide the amount of energy used by the data centre by the amount that is used by the computing equipment. The difference is going to be cooling and other overhead that supports the equipment and presumably everything else happening in a data centre building like lights, vending machines in the break room or whatever.

A PUE of 2 would mean that for every Watt that the computers use, you’d need to supply 2 Watts to the data centre. A PUE of 1 would be perfectly efficient. Microsoft data centres are 1.11-1.35, Amazon regions are 1.08-1.50, and Google’s data centres are 1.05-1.19. 1.05 is efficient! Google “data centers are more energy-efficient at delivering power specifically to computing chips than the electrical grid is at simply transmitting power.”

So what?

Data centres are really efficient.

Is PUE the only thing that matters for answering questions about data centre efficiency, sustainability or justice? No.

Does efficient mean that they have low emissions? Not necessarily.

Does that mean that everything data centres do is good? Of course not. They make the internet, “computing”, data centres, employers, social media, AI work. Some of those are essential, some can be damaging.

The bigger and more tricky questions are whether computing, AI etc are a net benefit to society, and (since they’re not going away) how to make them better and fairer.

---

1. Engine efficiency: The UK’s most popular car is the Ford Puma which has a 42 L tank and drives 5.4-6.6 L/100 km, which suggests a range of 636-777 km. Combustion engines are 11-27% efficient at converting petrol into movement, so you could imagine a Puma with the same efficiency as the average 1.3 PUE data centre (1.3 or 77%) having a range of 2,000 - 4,000 km. Human muscles are in the same range of efficiency as combustion engines, but I made up the bit about jumping over a data centre, sorry. At least I didn’t do the “tops of the PUEps” joke.↩︎

2. PUE numbers are self-reported and I imagine that if you’re running a data centre with a PUE above 1.67 ish you probably don’t put that in your marketing. Some companies don’t provide UK-level PUE detail, so I’ve used their global numbers. The list will have errors: data was collected in mid October - mid November 2025. Claude and ChatGPT helped find some of the urls for this post, but I checked their homework, and the errors will be mine. I’ve used some “new data centre” numbers I’ve mostly avoided numbers that talk about future plans. The Environment Agency/DESNZ data on Climate Change Agreements suggest that there are 65 different organisations in their Data Centre category, but the total number of UK data centre providers will be much larger. So the list here is definitely incomplete.↩︎