Nebius taps Caverion for €15m substation as its Mäntsälä footprint doubles to 145MW
Finnish technical services firm Caverion has signed a contract to design and deliver a substation connecting AI cloud company Nebius’s second Mäntsälä data centre to the electricity grid, with completion targeted for autumn 2027.
Martti Asikainen | 3.10.2026 | Photo by Caverion
Caverion Finland has signed an agreement with AI cloud company Nebius to design and deliver an electrical substation serving Nebius’s new data centre in Mäntsälä, Finland, according to a press release published by parent company Assemblin Caverion Group on 2 October.
The contract is worth approximately €15 million. The substation will serve a new 70-megawatt data centre building, located alongside Nebius’s existing 75-megawatt facility on the same site in Mäntsälä, a municipality roughly 60km north-northeast of Helsinki.
Combined, the two buildings would bring the site’s total capacity to 145 megawatts, based on the figures in the companies’ announcement.
A critical link to the grid
A substation converts electricity supplied at high voltage into a form a facility can use safely and continuously, acting as the data centre’s connection point to the wider power grid. Caverion describes it as one of the most important infrastructure components of a data centre as a whole, given that any interruption at this stage would affect the facility’s entire power supply.
Head of industrial projects and infrastructure at Caverion Finland, Kari Aalto, said the substation would be completed on an unusually fast timeline, which he described as typical for data centre construction projects.
He attributed the fast delivery to the experience of Caverion’s own project teams, precise phasing of the work, a local network of partner companies, and the company’s procurement and supply-chain management, drawing on lessons from the company’s previous substation projects.
Andrey Blokhin, senior vice president of global infrastructure at Nebius, said the Mäntsälä expansion was a key part of developing the company’s global AI infrastructure footprint, citing Caverion’s experience and delivery reliability as factors in the decision.
Part of a broader portfolio
The Nebius contract adds to a series of data centre and high-voltage infrastructure projects Caverion and Assemblin Caverion Group have secured recently in Northern Europe.
These include a technical construction and installation role at the Hyperco data centre in Kouvola, Finland; a €50 million contract as main contractor for an expansion of a high-security data centre in Estonia for MCF Group; technical installation work for a data centre expansion in Denmark; and an order from Coromatic for a data centre project in Stockholm.
Assemblin Caverion Group, formed through the combination of the Assemblin and Caverion brands, employs around 20,000 people across nine countries and reported SEK 42 billion (approximately €3.8 billion) in revenue over the past twelve months, according to the company.
