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Data centers can capture heat from servers and send it to nearby buildings or district-heating networks. That reuse can make heat a useful output, but it does not cool servers by itself: the facility still needs a reliable way to remove heat whenever the recipient cannot accept it.
How heat recovery fits into data-center cooling
Servers convert electrical energy into heat. A data center’s cooling system transfers that heat into air or a liquid loop; a heat exchanger can then transfer some of it to a building or heating network. The heat travels away from the computing equipment while being put to use elsewhere.
The temperature of the captured heat matters. Higher cooling-air or water temperatures leaving servers create more opportunities to use the heat directly, as the U.S. Department of Energy (DOE) explains in its 2024 Best Practices Guide for Energy-Efficient Data Center Design. If a prospective user needs hotter water than the data center can supply, a heat pump can raise the temperature—but it uses additional energy and adds equipment.
This is not a self-contained loop in which AI heat cools the AI. Heat reuse can help carry heat away from servers and deliver captured energy to another load. The facility must still be able to reject heat when reuse is unavailable or insufficient.
Where recovered data-center heat can go
Nearby buildings and low-temperature loads
When temperatures match, recovered heat can preheat water or ventilation air in a building. The DOE guide says direct use for low-temperature heating applications offers the greatest energy savings among the options it discusses, because it can avoid the extra step of upgrading the heat with a heat pump.
District-heating networks
A data center can connect to a local network that distributes heat to multiple customers. Whether that works depends on the network’s temperature requirements, the distance and cost of the connection, available demand, and the commercial arrangement between the operator and heat customers. Low-grade heat may need a heat pump before it can serve the network.
The International Energy Agency (IEA) reports that more than 20 data centers in Stockholm provide 1.5% of the city’s district-heating needs. It also reports that a cluster of new data centers in Espoo, Finland, is expected to provide enough waste heat for around 100,000 homes. The Espoo figure is an expectation reported by the IEA, not a measured result. These examples show what can be possible where heat networks and customers are available; they do not establish that every data center can reuse heat economically. See the IEA’s 2025 district-heating analysis.
Heat-powered cooling
Recovered heat can also drive an absorption chiller, which produces chilled water or air for other loads. This is a potential use identified by the Australian Department of Climate Change, Energy, the Environment and Water in its data-center guidance. Its feasibility and energy benefits depend on the particular equipment and site; there is no universal savings percentage to apply.
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Why heat reuse does not replace backup cooling
A heat customer may not need heat at every moment, and a network or heat-pump system may be unavailable. The data center therefore needs dependable equipment to remove heat independently of the reuse route. The DOE guide says that in most cases data centers have a redundant cooling system that can remove heat if the heat host is unavailable.
Heat recovery may reduce or, in some cases, eliminate the need for chillers; it may also reduce the use of evaporative cooling towers in some cases. Those are conditional outcomes, not a guarantee that a site can dispense with cooling equipment. The design must account for the site’s computing load, cooling system, heat recipient, and failure scenarios.
A DOE article about the National Renewable Energy Laboratory’s high-performance computing data center reports that equipment cooling accounts for 6% of its energy consumption, compared with 70% for a “typical data center.” Those figures describe the DOE article’s specific comparison, published in 2024; they are not a universal benchmark for modern data centers. The article is Technology Changes, but Energy Efficiency Principles Remain Steadfast in Data Center Design.
What determines whether a project makes sense
There is no universal best heat-reuse option. A project needs a viable match between the data center’s heat and a nearby use for it, as well as a robust plan for heat rejection. The DOE and IEA guidance points to several practical checks:
- Temperature match: Compare the heat available from the cooling loop with the delivery temperature the building or network requires. Direct use avoids heat-pump energy when temperatures already align.
- Distance and connection: Consider whether a suitable building, heat host, or district network is close enough for a workable connection.
- Timing and demand: Check whether heating demand coincides with the data center’s continuing heat output, including seasonal changes.
- Resilience: Determine how the facility will reject heat if the recipient cannot take it or reuse equipment is unavailable.
- Energy and water effects: Evaluate possible reductions in chiller or evaporative-cooling use alongside the energy and local design implications of heat pumps and other equipment.
- Commercial alignment: Set out who pays for equipment and connections, who operates them, and the terms for delivering and accepting heat.
How to interpret heat-reuse and climate claims
Heat leaving a server loop is not automatically useful heat. For EU data-center reporting, Commission Delegated Regulation (EU) 2024/1364 defines reused heat as energy used outside the data-center boundary that partly or fully substitutes energy otherwise needed outside it. The regulation measures the energy where it is handed to the other party and excludes the portion reused for cooling the data center from the reuse figure. This boundary distinguishes delivered, externally useful heat from heat that merely circulates inside the facility.
Likewise, a heat-reuse project does not automatically make a data center carbon-negative. The climate effect depends on what energy the delivered heat actually displaces and on the local infrastructure and equipment involved. A heat pump adds energy use; direct use at a suitable temperature may avoid that upgrade. Benefits should be assessed for the specific site and heat customer, not inferred from the amount of heat a facility produces.
The IEA’s 2025 Energy and AI report discusses liquid cooling as potentially providing heat at 40–80 °C and gives scenario costs of EUR 190,000–250,000 per MW of heat supplied, compared with over EUR 730,000 per MW for unabated natural-gas combined heat and power. These are report-specific scenario estimates, not prices or savings that can be assumed for an individual data center.
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