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Google’s Hamina data center in Finland uses seawater from the Bay of Finland for cooling. The site repurposed a former Summa paper mill and reused the mill’s existing pipes to the bay. Separately, Google and municipal utility Haminan Energia are developing offsite heat recovery that sends data-center heat into Hamina’s district-heating network. Google says the project is expected to cover about 80% of the network’s annual heat demand; that is a forecast, not a published measurement of achieved delivery.
What the Hamina project actually is
Hamina is a single Google data-center campus on Finland’s Gulf of Finland coast, not a commercial seawater-cooling product that can be installed at any facility. Google says it converted the former Summa paper mill and retained the mill’s seawater piping. In its 2024 Finland impact study, Google describes the resulting approach as “first-of-its-kind.” That characterization comes from Google and should not be read as an independently verified industry ranking.
The public descriptions establish seawater use and the inherited intake pipes, but they do not publish a complete process diagram. The reviewed material therefore does not establish whether every stage is open-loop, closed-loop, or a combination, nor does it specify the exact intake, heat-exchange, or discharge sequence.
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Bay water is the cooling source
Google identifies the Bay of Finland as the water source for cooling the Hamina facility. Using a nearby cold-water source can reduce reliance on conventional cooling arrangements, but the available facility documents do not state the site’s seawater intake volume, pumping power, discharge temperature, or seasonal operating profile.
The paper mill’s pipes are part of the reuse strategy
Rather than building an entirely new coastal intake route, Google says the data center uses pipes left from the former paper mill. Reusing that infrastructure is a site-specific design choice; it does not prove that the same arrangement would be practical or lower-impact at another coastal data center.
What is not publicly specified
- Annual or peak seawater intake volumes
- Detailed heat-exchanger and internal cooling-loop configuration
- Discharge location, temperature limits, and flow rates
- Independent measurements of local marine or ecosystem effects
Google’s impact study states a goal of protecting water quality and ecosystem health. A stated goal is not the same as a published, independent outcome measurement.
Heat recovery is a separate, linked project
From data-center waste heat to district heating
Google and Haminan Energia, the local municipal utility, have developed an offsite heat-recovery project. Recovered heat is routed to Hamina’s district-heating network, which serves homes, schools, and public-service buildings. This is distinct from the seawater cooling system: seawater provides a cooling source, while the heat-recovery project captures useful heat and transfers it to a municipal network.
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallThe 80% figure is an estimate
Google’s current Hamina facility page says the initiative is expected to meet an estimated 80% of district-heat demand. Google’s 2024 Finland impact study and a May 20, 2024 announcement by Ben Townsend, Google’s Global Head of Infrastructure & Sustainability, attribute the annual 80% figure to Haminan Energia’s estimate. The sources reviewed do not report annual megawatt-hours delivered or a measured percentage of demand actually supplied.
Rank #3
“Starting next year, our Hamina data center, nestled on the shores of the Gulf of Finland, is going to be both a hub for digital information and a source of sustainable heat for the district.”
— Ben Townsend, Global Head of Infrastructure & Sustainability at Google, May 20, 2024; describing the planned project
Google said in May 2024 that the heat project would start the following year, while its current location page says the facility has launched the initiative. Neither source supplies an operational performance series that would verify the forecast.
What the published numbers do—and do not—show
| Metric | Published value | Scope and qualification |
|---|---|---|
| District-heating coverage | About 80% of annual demand | Expected or estimated project coverage; not a reported measured result |
| Hamina PUE | 1.09 | Trailing-twelve-month value reported for 2026 Q1 and Q2 by Google |
| Google data-center fleet PUE | 1.09 in 2025 | Global fleet figure, not a Hamina-specific causal measure |
| Uptime Institute survey average | 1.54 in 2025 | Industry survey comparison reported by Google |
| Google investment in the region | €3.5 billion to date | Google-reported figure on the current Hamina page |
| Google Finland carbon-free energy | 98% in 2023 | Finland-wide Google figure, not a Hamina-only result |
| Operational waste diverted | 88% in 2025 | Global Google-owned and operated data-center figure |
| Water replenished | 7.7 billion gallons in 2025 | Global figure, about 78% of Google’s total freshwater consumption; not a Hamina seawater metric |
Power usage effectiveness (PUE) is the ratio of total facility energy to IT equipment energy. Hamina’s 1.09 indicates aggregate facility efficiency, but it cannot isolate the contribution of seawater cooling from servers, electrical systems, climate, heat recovery, or other loads.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Environmental claims: established facts versus open questions
Established by the available official descriptions
- The Hamina data center uses seawater from the Bay of Finland for cooling.
- The site reuses piping associated with the former Summa paper mill.
- Google and Haminan Energia are working on offsite heat recovery for Hamina’s district-heating network.
- Google presents 80% annual district-heat demand coverage as an expectation or estimate.
Not established in the reviewed material
- That seawater cooling alone produced Hamina’s PUE of 1.09
- The quantity of seawater withdrawn or returned
- Measured discharge temperatures or marine temperature changes
- Independent local ecological monitoring results
- Actual annual heat delivered to customers
Those gaps matter when comparing Hamina with another data center. A fair comparison needs facility-specific intake and discharge data, cooling-energy overhead, measured rather than projected heat delivery, and local ecological monitoring. It is not valid to assume seawater cooling always has a lower environmental impact without those comparable measurements.
Hamina’s possible expansion
On September 14, 2026, the City of Hamina reported that Google had purchased additional land for possible data-center expansion. The city said Google commissioned nature, environmental, and terrain surveys for zoning and land-use purposes. This is planning activity, not evidence that construction has begun or that the survey findings are complete.
Google separately announced at least €13 billion in planned investment in Finnish digital infrastructure for 2027–2028. That is a future plan and should not be combined with the €3.5 billion Google reports as invested in the region to date.
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How to interpret the project responsibly
- Keep the systems separate. Seawater cooling concerns the facility’s heat-rejection or cooling supply; district heat recovery concerns exporting useful heat to Haminan Energia’s network.
- Label estimates as estimates. The 80% figure is expected annual coverage, not a published operating result.
- Use the right boundary for each statistic. Hamina PUE is site-specific, while carbon-free energy, waste diversion, water replenishment, and fleet PUE figures are broader Google metrics.
- Do not infer ecological outcomes. Without intake, discharge, and independent monitoring data, the public record cannot quantify local marine impact.
- Treat expansion announcements as plans. Land acquisition and surveys indicate possible future development, not completed capacity.
Frequently Asked Questions
Is Google cooling all of its data centers with seawater?
No. The seawater system described here is specific to Google’s Hamina data center in Finland and its coastal, former-paper-mill infrastructure.
Has the Hamina heat project already supplied 80% of district-heating demand?
The available official sources describe 80% as an expected or estimated annual share. They do not publish measured annual heat delivery or a verified realized percentage.
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