A Finnish district-heating network has used data-center heat since 2015.

Server rooms produce a steady stream of low-temperature heat. In Mäntsälä, heat exchangers capture warmth from the data center’s exhaust air and electric heat pumps lift it to the temperature required by the district network. Nivos then distributes it to properties connected in the town centre.

The network and a nearby customer base matter as much as the servers. Nivos keeps other heat sources available for reliability, and a 2025 municipal assessment says expanding the existing network northward is difficult without larger heat customers.

The sources describe different periods and measures. A Nivos reference updated in 2019 described 30 gigawatt-hours a year after a 2018 enhancement. Equipment supplier Calefa’s undated reference cites 25 gigawatt-hours a year. Nebius estimated roughly 20,000 megawatt-hours annually in October 2024. The most recent utility statement Bright found, from August 2025, says recovered heat supplied about one-third of the town-centre network.

Bright therefore does not present one timeless annual-output number. The operating fact is clear; current metered delivery, heat-pump electricity, price, and displaced emissions still need consistent annual disclosure.

Connected homes and other properties receive district heat, but the public sources do not identify individual customers. The result depends on a utility willing to buy and move the heat, sufficient nearby demand, electric heat pumps, pipes, commercial terms, and backup supply.

The original operator was Yandex. Nivos now identifies the operating company as Global DC Oy, wholly owned by Nebius Group.