Fortum and Microsoft Commission 350 MW Data Center Waste Heat
- Cooling & Heat Recovery Data Centers Efficiency & Optimization News
Marin Holt
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- 5 minutes read
- 350 MW combined thermal capacity from two heat pump plants at Espoo and Kirkkonummi data center sites
- EUR 225 million investment by Fortum covering heat pump plants, DN700 pipeline connections, and network upgrades from 2023-2027
- 400,000 tonnes of CO2 eliminated annually, meeting 2-3% of Finland national emission reduction targets
- 250,000 residents served across Espoo, Kauniainen, and Kirkkonummi through 900 km underground pipe network
- 75% of data center waste heat captured for district heating, supplying 40% of regional demand
Fortum and Microsoft are bringing online the world’s largest data center waste heat recovery system during the 2025-2026 heating season in southern Finland. The two heat pump plants, located at Microsoft’s data center sites in Espoo and Kirkkonummi, deliver a combined thermal capacity of 350 MW to Fortum’s district heating network, serving approximately 250,000 residents across Espoo, Kauniainen, and Kirkkonummi.
Critical Perspective
The article states 350 MW of thermal capacity. Vattenfall’s Berlin project recovered 20 MW from a data center. The Drax biomass plant faced scrutiny over its carbon accounting. What is the actual net carbon reduction from this project?
What Is Being Built
The system captures waste heat from Microsoft’s server halls and converts it into district heating through water-to-water heat pumps. The Kirkkonummi plant, constructed by AFRY as EPCM contractor, includes air-to-water heat pumps, two electric boilers, and a 20,000-cubic-meter thermal accumulator tank that buffers supply during peak demand periods. Fortum invested approximately EUR 225 million between 2023 and 2027 to build the heat pump plants, pipeline connections, and network upgrades. DN700 district heating pipes manufactured by Isoplus connect the facilities to Fortum’s existing 900 km underground distribution network.
The data centers operate on 100% emission-free electricity. Approximately 75% of their waste heat feeds into the district heating network, supplying about 40% of the total district heating demand in the service area. Once fully operational, waste heat sources will account for roughly 60% of the region’s district heating, with 40% from the data centers and 20% from other sources including purified wastewater.
Critical Analysis
The 350 MW heat pump system concentrates VFD-driven compressor loads at two sites on Fortum’s 110 kV network in Espoo and Kirkkonummi. Concentrating 350 MW of VFD-driven heat pump load at two grid nodes creates significant harmonic stress; without active filtering, THDv at the 110 kV PCC risks exceeding IEEE 519-2022 Table 1’s 5% limit for the 1-69 kV voltage class.
Why It Matters
The project eliminates approximately 400,000 tonnes of CO2 emissions annually, meeting 2-3% of Finland’s national emission reduction targets from a single installation. Fortum selected the data center locations specifically for waste heat integration with existing district heating infrastructure, a design approach that other Nordic and European utilities are studying as a template. The European Union backed the project with NextGenerationEU funding, and Germany’s Energy Efficiency Act now requires new data centers to utilize at least 10% of waste heat starting July 2026, rising to 20% by 2028. The Fortum-Microsoft system demonstrates that data center waste heat recovery operates at utility scale, converting what is typically a cooling liability into a revenue-generating thermal asset worth EUR 12-30 per MWh to district network operators.
