Summary
- Nebius disclosed 65,001 tCO2e of market-based Scope 1 and 2 emissions for 2025.
- Its 2024 disclosure was 2,036 tCO2e, producing the approximately 32x cross-report comparison.
- The company says 99% of its 2025 market-based Scope 1 and 2 total came from data-centre operations.
- Nebius expanded its operating base to seven active sites, so the two annual totals are not a constant-site efficiency test.
- Scope 3 was not calculated because boundaries, supplier data and reporting systems were not mature enough for a representative inventory.
- A portfolio PUE of 1.25 and Finland-1 WUE of 0.018 litres per kWh are useful operating measures, but neither completes the carbon account.
Thirty-two times is a change in totals, not a diagnosis
Dividing 65,001 by 2,036 produces the headline ratio. It does not say how much of the increase came from more sites, higher utilisation, a different electricity mix, backup generation or changes in organisational boundary. A valid like-for-like efficiency comparison would hold those variables steady or reconcile them.
Nebius instead gives the central structural explanation: its operating base reached seven active sites. That makes the larger total economically intelligible. An AI-cloud company adding powered capacity will usually consume more energy before efficiency measures can offset absolute growth.
The correct conclusion is therefore narrower than “efficiency collapsed”. Nebius's market-based operational footprint expanded sharply. The report has not yet supplied the bridge needed to isolate growth, mix and efficiency effects.
The 99% concentration identifies the control surface
Nebius attributes 99% of market-based Scope 1 and 2 emissions to data-centre operations. That points management attention toward electricity procurement, generator choices, cooling, workload scheduling and the pace at which new halls are occupied.
It also limits the value of broad corporate-office initiatives. A small reduction in travel or office energy cannot materially counter a rapidly growing compute estate. Decisions about where and how capacity is powered dominate the disclosed operational total.
Market-based accounting reflects contractual instruments and supplier-specific factors where available. A fuller account would show location-based results alongside it, site-level energy use, renewable-contract quality and the contribution of direct fuel consumption.
Scope 3 is the largest unanswered boundary
AI infrastructure is material-intensive. Servers, accelerators, racks, electrical equipment, construction materials and logistics all carry embodied emissions before a workload begins. Nebius says its supplier and activity data were not yet sufficient for a representative 2025 Scope 3 inventory.
That is a transparent limitation, but it prevents readers from treating 65,001 tCO2e as the company's full climate footprint. Rapid construction can make the omitted boundary especially important in a growth year.
The next report needs a defined organisational boundary, category coverage, estimation methods and a restated baseline if the method changes. Without them, reductions in operational electricity emissions could coexist with rising embodied emissions out of view.
PUE and WUE answer different questions
The reported portfolio-weighted PUE of 1.25 describes how much facility energy accompanies IT energy. It is not a carbon-intensity measure: two sites with the same PUE can have very different emissions if their electricity and backup generation differ.
The Finland-1 WUE of 0.018 litres per kWh is site-specific. Nebius attributes it to closed-loop liquid cooling and air-based free cooling. Climate and engineering conditions in Finland cannot automatically be assigned to every site in the United States, Europe or the Middle East.
Both metrics are useful when their denominators, measurement periods and site coverage are stable. They should appear beside, not in place of, energy, emissions and water totals.
Fuel cells relocate rather than erase the question
Nebius highlights planned deployment of 328MW of behind-the-meter solid-oxide fuel-cell capacity at a US site. Fuel cells can reduce local pollutants and water use relative to some combustion technologies, and on-site generation can accelerate access to power.
The fuel source remains decisive. If natural gas supplies the cells, greenhouse-gas emissions continue even though electricity is generated electrochemically rather than through a turbine. Upstream methane and contractual fuel assumptions also matter.
The 328MW figure is planned generation capacity, not a 2025 operating result and not IT load. Future reporting should separate generation output, fuel input, emissions intensity, availability and the load actually served.
Targets must now catch up with capacity
Nebius says quantified emissions-reduction and resource-use targets are still being developed. That was understandable during corporate formation; it becomes less satisfactory as site count and power procurement accelerate.
A credible target would identify the baseline, operational boundary, Scope 3 coverage, absolute and intensity measures, interim dates and treatment of acquisitions or new campuses. It would also distinguish contractual renewable claims from physical hourly matching.
The 2025 report establishes that data-centre growth has become the company's dominant disclosed climate mechanism. The next test is whether its accounting and targets can expand as quickly as its infrastructure.