Don’t get greenwashed away: How data centre operators can make their ESG reports count

Executive Summary

• Structure Research notes that while data centre operators have made ‘great strides’ in reporting their ESG metrics, ‘significant variation’ remains in disclosures
• Iron Mountain was adjudged a leader in transparency and performance in renewable energy, with carbon, power and water usage effectiveness all the lowest they’ve ever been but also with key messaging points around it
• A key facet in the best ESG reports is in tying sustainability initiatives to business outcomes, with a good example being Compass’ partnership with Vertiv for the CoolPhase Flex hybrid liquid cooling unit

ESG (environmental, social and governance) reporting across the data centre industry is becoming increasingly common – yet ‘significant variation’ remains in the scope and depth of disclosures.

That is the takeaway from a recent report by Structure Research. The 2025 State of Environmental Impact study, published last February, analysed sustainability metrics from 26 data centre operators and nine hyperscale cloud platforms.

In terms of the numbers, it is a mixed bag. Overall, total data centre water usage grew 9.6% between 2019 and 2024. Total emissions grew by 12.1% in the same timeframe. Yet data centre operating PUE (power usage effectiveness) continues to tick downwards, from 1.44 in 2019 to 1.38 for data centre providers in 2024. While energy usage has overall grown 17.9% in those five years, renewable energy usage has grown 27.9%.

These numbers emphasise the complexity of sustainability for data centres – and the importance of transparent, credible reporting by operators.

A tool to encourage reporting standardisation

Structure Research, as part of its report, published the Structure Research Sustainability Quadrant (SRSQ) and ranked leading organisations based on three primary attributes. These were levels of transparency, operational data centre efficiency, and renewable energy usage.

The analyst said the variance between those in terms of reported data, even within leaders, was ‘striking’. Transparency was prioritised, therefore, to ensure organisations are not tempted to only report data which reflects positively on their operating metrics. The SRSQ takes PUE, carbon intensity and water intensity into account for operational performance, and percentage of renewable energy used relative to the total energy usage of a provider’s data centre footprint.

While such a quadrant does not enable an exact ranking, the strongest performers in terms of transparency were Iron Mountain and NEXTDC, who both scored the maximum available. The former also achieved a maximum score for renewable energy.

Data Centre Insight looks at the best ESG reports from data centre operators to show what they’re doing well – and how it can help you.

Be clear, be sincere – and don’t neglect the ‘S’

Iron Mountain publishes two documents each year; an overall sustainability report, and a shorter data centre sustainability overview. So, what is the New Hampshire-headquartered company doing so well in this regard?

Carbon usage effectiveness (CUE), PUE and WUE are at their best levels ever, as well as aligning with all Climate-Neutral Data Centre Pact targets. New builds are also aligned with BREEAM sustainable building certification criteria. This is ahead of target for the company. The numbers are towards the back of the report but are easily accessible. PUE is at 1.41, down from 1.44 the year before, while WUE is below 1 (0.996) as ‘particularly significant improvement’. CUE is at 0.039.

A theme which stands out is one of not standing still. Referring to being ahead of schedule for BREEAM certification, the report note: “Achieving these goals on or ahead of schedule underlines the realistic nature of our environmental impact reduction program. It also allows us to simplify and refocus our environmental goals and focus more effort on new initiatives.”

Another key area for Iron Mountain is in the ‘S’ side, an area which is easy to overlook. “We want to be the best possible service provider and neighbour, and I’d like to take this chance to congratulate all the employees who consistently go the extra mile, whether it is to satisfy our customers or to support the communities where we operate,” wrote Gary Aitkenhead, EVP and GM. “A customer Net Promoter Score of +54.2 and 41,759 volunteer hours create a great platform to build on, and one we should be proud of.”

Messaging: Outcomes, not optics

Elsewhere, Compass Datacenters’ 2025 report, the company’s third, makes it clear from the very first word: it is about outcomes. The decision was taken to frame the annual report to the Outcomes Report to help create the link between innovations and tangible business and ESG results. “Another year of opting to report because it’s the right thing to do… and another year of measuring success by outcomes rather than optics,” CEO Chris Crosby wrote.

The company posted a PUE of 1.25 and an impressive water usage effectiveness (WUE) of 0, attributed to closed-loop water systems and being zero-water from inception for IT loads. An example of an initiative with outcome is in a partnership with Vertiv to develop the Vertiv CoolPhase Flex, a hybrid liquid cooling unit allowing for both liquid and air cooling capabilities. Compass explicitly notes the unit allows the company ‘to eliminate water use in cooling while achieving power usage efficiencies below the industry average.’

The message from NTT GDC CEO Doug Adams, in the company’s Shaping a Sustainable Future report, is much the same as Compass. “We prioritise sustainability not just because our clients demand it, but because it’s the right thing to do,” he wrote.

NTT scored above average in the SRSQ for transparency. The company’s goals are clear, based on reaching Net Zero emissions 10 years ahead of the Paris Agreement; reduced Scope 1 and Scope 2 emissions in data centre operations by 90+ vs. FY21 baseline, and by 2040 reduced total Scope 1 to 3 emissions through the supply chain to Net Zero. This translates in the most recent report to 28% emission reduction in Scope 1 and 2 operations and 60% renewable energy in operations (Scope 2). Average annual PUE and WUE was 1.38 and 0.72/1.42 respectively.

The sustainability mission outlines the five-step process for the company; regularly review and update Net Zero strategy; ensure results are externally validated and communicated; improve internal awareness and capabilities to create a sustainability culture in the organisation; make products future-proof; and be climate resilient to ensure business continuity and investor interest.

Overall, however, Structure Research notes that while it is ‘important to be transparent about the operations and sustainability of data centres… companies have made great strides in reporting their ESG metrics.’

Read more: PUE isn’t enough anymore – here’s the metrics that matter in 2026

Photo by Davis Fabrini