Summary
- Nebius reported a portfolio PUE of 1.25 and WUE of 0.018 litres per kWh at its Finnish facility.
- Market-based Scope 1 and 2 emissions reached 65,001 tonnes of CO₂ equivalent.
- Renewable procurement should reduce reported operational emissions, although Scope 3 remains incomplete.
Nebius reported market-based Scope 1 and Scope 2 emissions of 65,001 tonnes of CO₂ equivalent in 2025 as the expansion of its data centre estate outweighed efficiency gains in cooling, power management, and heat reuse.
Data centre operations accounted for 64,095 tonnes of the disclosed market-based total. Location-based Scope 1 and Scope 2 emissions were lower at 30,914 tonnes, including 30,028 tonnes from data centres.
The infrastructure provider reported a portfolio-average power usage effectiveness of 1.25 and water usage effectiveness of 0.018 litres per kWh at its owned Finland facility. Its Mäntsälä site exported 19.5GWh of recovered heat during the year.
Power contracts change the carbon account
The difference between Nebius’s market-based and location-based totals arose principally in Finland. The national grid has a comparatively low average carbon intensity, but the market-based calculation applied a higher residual-mix factor because the facility did not hold matching renewable-energy attributes for all electricity consumed during the reporting period.
Nebius said Finland-1 used grid electricity during 2025. Its production-mix factor was 33g of CO₂ equivalent per kWh, reflecting a grid that was more than 95% low carbon, while the residual-mix factor used in the market-based calculation was 406g.
A power purchase agreement signed during the first half of 2026 is expected to cover the Finnish facility with renewable electricity. Future market-based totals should fall if the contractual instruments match the reporting boundary and consumption, although physical demand from the site will continue to grow as more compute is installed.
Nebius’s 2025 sustainability report records direct Scope 1 emissions of 3,840 tonnes and market-based Scope 2 emissions of 61,161 tonnes.
Scope 3 emissions were not included because the company said its inventory was not sufficiently complete. The omission leaves construction, equipment manufacture, servers, accelerators, network hardware, and other value-chain emissions outside the reported total.
Fugitive refrigerant data were also incomplete. Nebius said it is strengthening its methods and controls, which may widen the reported footprint even as operational efficiency improves.
Absolute growth outruns facility ratios
A PUE of 1.25 indicates comparatively efficient supporting infrastructure, but it does not limit the electricity used by IT equipment. A larger facility can improve its PUE while increasing total power consumption and emissions.
The same distinction applies to water. Nebius’s WUE figure at Finland-1 reflects closed-loop liquid cooling and extensive use of free cooling, reducing reliance on evaporative systems. The company has modelled potential water avoidance of 3.3 billion litres per GW each year compared with more water-intensive designs, but that is not a measured reduction against the site’s previous consumption.
Heat reuse produces a physical output beyond a reporting ratio. The Mäntsälä facility exported 19.5GWh into the district-heating system during 2025, and the connection is designed to deliver more than 250GWh annually at full capacity.
The amount accepted will depend on seasonal heat demand, network temperatures, heat-pump performance, commercial terms, and the pace at which the data centre reaches higher utilisation. Export capacity does not guarantee that every available unit of heat will be used.
Nebius is expanding beyond Mäntsälä, including a planned 310MW AI facility at Lappeenranta and a 240MW project near Lille. The scale of those developments will make absolute electricity demand the dominant environmental measure, even where each building performs efficiently.
European reporting is moving towards more detailed disclosure of electricity, water, waste heat, and operational efficiency. Comparisons will require common boundaries and consistent treatment of renewable contracts, colocation capacity, construction emissions, and customer hardware.
Nebius has disclosed enough detail to explain why its two carbon accounting methods produce different results. The market-based increase does not mean the Finnish grid suddenly became more carbon intensive; it reflects the contractual attributes attached to the electricity consumed.
Renewable procurement can reduce the reported total and support new generation where contracts are additional and well structured. It cannot replace the physical requirement for firm electricity at every hour, nor does it account for emissions embodied in a rapidly expanding estate.
The company’s cooling and heat-reuse performance demonstrates that efficient facilities can reduce the environmental cost of each unit of compute. The absolute footprint will still rise if capacity, utilisation, and equipment deployment grow faster than those efficiency gains.
