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Data centers can turn nearly all of the electricity they consume into a useful heat source—but only when the recovery system, heat customer, and surrounding infrastructure are designed to work together. Heat exchangers capture energy from server cooling systems, heat pumps raise its temperature when necessary, and insulated pipework delivers it to district-heating networks, homes, greenhouses, swimming pools, or industrial users.
The construction challenge is not simply removing heat from a building. It is creating a reliable connection between a continuous, high-density heat source and a customer whose temperature, distance, timing, and reliability requirements all match.
Why data centers produce so much heat
Servers, processors, storage equipment, power supplies, pumps, fans, and other electrical systems consume energy. Almost all of that electricity ultimately becomes heat.
As a practical energy-balance approximation, 1 MWh of electricity consumed produces approximately 1 MWh of heat. That does not mean 1 MWh will automatically become 1 MWh of useful heat. Cooling losses, temperature requirements, heat-pump electricity, pipe losses, maintenance, and periods of low demand reduce the amount that can actually be delivered.
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- Exceptional Performance: The heat exchanger has a capacity of 42,000 Btu. Depending on the application, the heat exchanger can produce up to 360kBtu of heat per hour, with 12 aluminum fins and 3 rows of 3/8" seamless copper tubes per inch. The combination of wavy fins and seamless copper tubes, which enhanced contact areas both inside and outside the tubes, increasing in heat transfer performance, maximizing heating or cooling efficiency
- Premium Material Construction: Our heat exchangers are supported by steel shells, and the edges and contact points are base brazed, which is very solid and not easily affected by high pressure and temperature. Copper and aluminum are highly conductive materials, which make the heat exchanger have good performance and economy in heat transfer and cooling. The fins are coated with epoxy resin, which improves the hardness and wear performance of the fins, prolonging the service life of the fins
- Energy-efficient and Affordable: Our water-air heat exchangers allow for water-air heat exchange movement through a variety of sources - boilers, solar panels, etc. This means you can utilize a variety of renewable energy sources and save energy
- Convenient Installation: This new type of heat exchanger is easy to install, with a variety of options available. It can be directly connected to the pipeline and fixed with clamps; it also can be directly welded to the pipeline and adapters or be connected with rivets to meet a multitude of installation needs
- Multiple Applications: Water-to-air heat exchanger offers a high level of thermal efficiency and durability in a compact and lightweight unit, which maximizes space saving, suitable for Outdoor Wood Furnaces, Residential and Commercial Heating and Cooling, Hybrid Systems, Air Conditioning, Inverter Cooling, and so on
It is useful to separate four different quantities:
- Heat generated: roughly equivalent to the facility’s energy consumption.
- Heat technically recoverable: the portion that can be captured at a useful temperature.
- Heat economically recoverable: the portion that can be transported and used at an acceptable cost.
- Heat actually reused: the energy delivered to and consumed by an external customer.
Microsoft’s heat-reuse explanation provides the approximate 1 MWh-to-1 MWh relationship and distinguishes potential reuse from practical system performance.
From server to building: how heat recovery works
A typical recovery system follows this chain:
Server → cooling loop → heat exchanger → heat pump → thermal storage → district-heating network → homes or businesses
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Heat can be collected from hot server exhaust air, rack-mounted rear-door heat exchangers, direct-to-chip cold plates, or immersion-cooling systems.
2. Separate the fluid loops
A plate or other heat exchanger transfers energy from the data center’s cooling circuit into a separate heating circuit. Keeping the loops separate helps manage differences in pressure, water quality, corrosion risk, contamination, and fluid compatibility.
3. Raise the temperature when required
Recovered heat may be warm enough for low-temperature uses but too cool for an existing district-heating network or domestic-hot-water system. A heat pump then raises the output temperature. This makes the heat more useful, but the heat pump consumes electricity and must be included in efficiency and emissions calculations.
4. Store and balance the heat
Data centers commonly operate continuously, while heating demand changes with weather, time of day, weekends, and seasons. Thermal storage can bridge that mismatch. For example, the announced Equinix–A2A Milan project includes two thermal-storage systems totaling 6,000 cubic meters.
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5. Export the heat
Insulated pipework can deliver heat to district-heating networks, nearby buildings, greenhouses, fish farms, industrial processes, domestic-hot-water systems, or swimming pools. Shorter connections and lower required temperatures generally improve the economics.
Why cooling technology affects construction feasibility
Cooling is not just an operational issue. It determines the temperature, concentration, pipework, plant-room requirements, and retrofit difficulty of the recoverable heat.
Conventional air cooling
Air-cooled facilities supply cool air through cold aisles, draw it across servers, collect hot air in hot aisles, and reject the heat through air handlers, chillers, cooling towers, dry coolers, or outside air.
Rank #2
- Exceptional Performance: The heat exchanger has a capacity of 67,500 Btu. Depending on the application, the heat exchanger can produce up to 360kBtu of heat per hour, with 12 aluminum fins and 3 rows of 3/8" seamless copper tubes per inch. The combination of wavy fins and seamless copper tubes, which enhanced contact areas both inside and outside the tubes, results in a 10-20 percent increase in heat transfer performance, maximizing heating or cooling efficiency
- Premium Material: Our heat exchangers are supported by steel shells, and the edges and contact points are base brazed, which is very solid and not easily affected by high pressure and temperature. Copper and aluminum are highly conductive materials, which make the heat exchanger have good performance and economy in heat transfer and cooling. The fins are coated with epoxy resin, which improves the hardness and wear performance of the fins, prolonging the service life of the fins
- Energy-efficient and Affordable: Our water-air heat exchangers allow for water-air heat exchange movement through a variety of sources including boilers, solar panels, and more. This means you can utilize a variety of renewable energy sources and save energy
- Convenient Installation: This new type of heat exchanger is easy to install, with a variety of options available. It can be directly connected to the pipeline and fixed with clamps; it also can be directly welded to the pipeline and adapters or be connected with rivets to meet a multitude of installation needs
- Multiple Applications: Water-to-air heat exchanger offers a high level of thermal efficiency and durability in a compact and lightweight unit, which maximizes space saving, suitable for Outdoor Wood Furnaces, Residential and Commercial Heating and Cooling, Hybrid Systems, Air Conditioning, Inverter Cooling, and more
Air is convenient but relatively diffuse. A recovery retrofit may require the following sequence:
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesServer air → air-to-liquid heat exchanger → water loop → heat pump → heat network
That additional transfer stage can require hot-aisle containment, new air-handling equipment, pumps, controls, structural modifications, and space for heat-exchange plant. It is often most suitable where an existing facility already has a nearby heat customer and cannot economically replace its server cooling architecture.
Direct-to-chip cooling
Direct-to-chip systems attach cold plates to processors and other high-power components. Heat is collected close to the source and transferred into a controlled liquid loop.
The IEA 4E liquid-cooling assessment identifies direct-to-chip, immersion, and rear-door heat exchangers as the principal liquid-cooling technology families and describes direct-to-chip single-phase cooling as the most mature and widely deployed of the three in its assessment.
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For new high-density AI facilities, direct-to-chip cooling can simplify heat capture, support higher rack densities, and reduce dependence on large room-air systems. It also requires compatible servers, cold plates, manifolds, coolant-distribution units, leak detection, filtration, corrosion control, and maintenance procedures.
Immersion cooling
Immersion cooling places servers or components in dielectric fluid. It can provide highly concentrated heat transfer for specialized high-density workloads, but it changes the building’s servicing, fluid-management, warranty, fire-safety, and equipment-handling requirements. It is generally more suitable for facilities designed around immersion than for routine retrofits.
Rear-door heat exchangers
Rear-door units attach to selected racks and capture hot exhaust air without placing coolant directly on server components. They can be useful for targeted high-density zones in an otherwise air-cooled facility, although the system remains partly dependent on airflow and rack-level equipment.
Heat recovery is not the same as data-center efficiency
“Efficiency” can mean several different things in this context:
| Measure | What it indicates | What it does not prove |
|---|---|---|
| PUE | Facility overhead energy compared with IT energy | How much external heat is reused |
| ERF | The share of data-center energy reused outside the facility | Whether the reused heat displaces high-carbon energy |
| COP | Heat-pump heat output relative to electricity input | The project’s complete lifecycle emissions |
| Net emissions benefit | Avoided emissions minus added electricity, construction, pumping, backup, and refrigerant impacts | That recovery is beneficial in every location |
Recovering heat does not make servers consume less electricity, and it does not eliminate the need for cooling. It changes where the heat goes and may reduce the energy required to reject it.
Rank #3
- 【Excepetional Performance】The heat exchanger has a capacity of 110,000 Btu. Depending on the application, the heat exchanger can produce up to 360kBtu of heat per hour, with 12 aluminum fins and 3 rows of 3/8" seamless copper tubes per inch. The combination of wavy fins and seamless copper tubes, which enhanced contact areas both inside and outside the tubes, increasing in heat transfer performance, maximizing heating or cooling efficiency.
- 【Premium Material】Our heat exchangers are supported by steel shells, and the edges and contact points are base brazed, which is very solid and not easily affected by high pressure and temperature. Copper and aluminum are highly conductive materials, which make the heat exchanger have good performance and economy in heat transfer and cooling.The fins are coated with epoxy resin, which improves the hardness and wear performance of the fins，prolonging the service life of the fins.
- 【Energy-efficient and Affordable】Our water-air heat exchangers allow for water-air heat exchange movement through a variety of sources - boilers, solar panels, etc.This means you can utilize a variety of renewable energy sources and save energy.
- 【Convenient Installation】This new type of heat exchanger is easy to install, with a variety of options available. It can be directly connected to the pipeline and fixed with clamps; it also can be directly welded to the pipeline and adapters or be connected with rivets to meet meet a multitude of installation needs.
- 【Multiple Applications】Water-to-air heat exchanger offers a high level of thermal efficiency and durability in a compact & lightweight unit, which maximizes space saving, suitable for Outdoor Wood Furnaces, Residential and Commercial Heating and Cooling, Hybrid Systems, Air Conditioning, Inverter Cooling, and so on.
Microsoft estimates that, under specified conditions, an air-cooled data center could achieve an Energy Reuse Factor of up to approximately 69% in winter and 86% in summer. These are estimates, not universal measured results. They should be treated as design-specific illustrations rather than performance guarantees.
The environmental case depends on what the recovered heat replaces. Heat displacing a gas boiler may deliver a clear benefit. Heat requiring a large temperature lift from a carbon-intensive electricity supply may deliver a smaller benefit. An already low-carbon district-heating network may also leave less fossil fuel to displace.
Projects showing how the model is developing
Microsoft and VEKS, Høje-Taastrup, Denmark
Microsoft says surplus heat from a data center in Høje-Taastrup is being captured through an air-to-liquid heat exchanger and redirected to the local district-heating network. The project is expected to provide heat for approximately 6,000 homes, with first deliveries expected during the 2025–2026 heating season, according to Microsoft’s project description.
The construction lesson is straightforward: a nearby district-heating network, a heat pump, and concentrated residential demand can make a relatively direct connection possible.
Microsoft, Fortum, and AFRY, Finland
A World Economic Forum case study reports that Microsoft’s planned data centers in Espoo and Kirkkonummi are being integrated with Fortum’s regional district-heating network. The project is reported at up to 350 MW of thermal capacity and could cover approximately 40% of district-heating demand across Espoo, Kauniainen, and Kirkkonummi once fully developed.
Those figures describe planned or expected capacity and demand coverage, not continuously delivered output under every operating condition.
Equinix and A2A, Milan
Equinix and A2A announced a July 2, 2026 collaboration to recover heat from Equinix’s Milan-area campus. The company-announced design includes four heat pumps with total capacity of 72 MW, 6,000 cubic meters of thermal storage, and up to 225 GWh of thermal energy annually. It is expected to provide heat for more than 21,000 homes.
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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →A2A and Equinix also say the project could increase heat distributed through Milan’s district-heating network by roughly 20% and avoid more than 345,000 metric tons of CO2. These are forecasts and company claims, not independently verified operating results. Details are available in the project announcement.
Equinix and Markham District Energy, Ontario
Equinix describes an existing arrangement in Markham, Ontario, where recovered data-center heat supports local buildings through Markham District Energy. The project demonstrates how municipal energy infrastructure can provide an outlet for otherwise rejected heat. Quantified annual delivery and emissions results should be confirmed through district-energy or municipal operating data rather than inferred from the operator’s description.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why location matters more than the size of the data center
A large data center in an isolated location may have no practical heat-reuse market. A smaller facility beside a district-heating main, greenhouse, factory, or swimming pool may be more valuable.
Rank #4
- High-Quality Materials: Made of 316L stainless steel with 99% copper brazing at edges and contact points, forming a robust and leak-resistant unit that withstands high pressure and temperature. UL and CE certified for reliable quality.
- Efficient Heat Transfer: The high-conductivity stainless steel plates feature an asymmetrical herringbone pattern, creating intense pressure turbulence for efficient heating/cooling. With up to 99% heat efficiency, it generates 500-660K BTU per hour, saving pump power and electricity, reducing overall application costs.
- Large Heat Exchange Area: The heat exchanger features 5”x12” plates with up to 50 plates, providing excellent heat transfer performance for maximum efficiency. Suitable for operating temperatures from -292℉ to 392℉.
- Tight and Leak-Proof: To eliminate the possibility of micro-leaks, the heat exchanger uses high-pressure vacuum brazing and undergoes helium leak testing, ensuring long life and high reliability.
- Stable Installation: Includes two stainless steel brackets made of 304 stainless steel, offering excellent rust resistance and stability for easy and secure mounting of the heat exchanger.
The IEA’s guidance emphasizes site-specific assessment of economics, technical feasibility, nearby demand, temperature, existing infrastructure, legal conditions, and contracts.
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During site selection, developers should map:
- Existing district-heating mains and spare network capacity.
- Buildings with year-round heat or hot-water demand.
- Industrial processes that can use low- or medium-temperature heat.
- Required delivery temperatures and pressure levels.
- Distance, route constraints, easements, and road crossings.
- Space for heat pumps, storage tanks, substations, and backup equipment.
- Planning, permitting, environmental, and utility-connection requirements.
Hot water is easier to transport than low-grade warm air, but long pipe routes still involve capital costs, heat losses, pumping energy, maintenance, and complex ownership arrangements.
The construction and commercial issues that determine success
Temperature matching
Designers must establish the temperature available from the data-center loop and the temperature required by the customer. Direct low-temperature uses can avoid or reduce heat-pump work. Higher-temperature district heating, domestic hot water, and industrial processes may require a substantial temperature lift.
Seasonal demand
Data centers can produce heat throughout the year, while space-heating demand falls in summer. The project needs a plan for warm weather, mild winters, weekends, holidays, and heat-network outages. Options include thermal storage, supplemental boilers, alternative customers, heat rejection equipment, or a combination of these.
Reliability and redundancy
Heat export must never compromise IT uptime. The facility should retain independent backup cooling, bypass capability, redundant pumps and heat exchangers, and controls that prioritize server protection. Contracts should define whether heat supply is firm, interruptible, seasonal, or available only when the data center has surplus capacity.
Water and coolant management
Closed-loop direct-to-chip systems can avoid ongoing evaporative water loss in certain designs, as Microsoft explains in its water-intensity discussion. That is not the same as zero water use across construction, maintenance, makeup water, manufacturing, and the wider supply chain.
Liquid systems also require coolant-quality control, leak detection, corrosion protection, filtration, compatible materials, and documented maintenance procedures.
Contracts and ownership
A viable project must allocate responsibility for the connection, heat pumps, storage, metering, maintenance, energy costs, outages, insurance, and future expansion. The parties also need a clear price or valuation for the heat and rules for emissions accounting.
How to evaluate a proposed heat-reuse project
- Measure the source. Establish IT load, cooling load, operating hours, available temperatures, flow rates, and expected future rack density.
- Identify the customer. Confirm a real heat offtaker rather than relying on a theoretical nearby market.
- Compare temperatures. Determine whether heat can be used directly or requires a heat pump.
- Model the route. Include pipe length, insulation, easements, pumping energy, construction disruption, and thermal losses.
- Model time. Test winter, summer, outages, maintenance, changing server loads, and customer shutdowns.
- Protect resilience. Design bypasses and backup cooling so the export system cannot threaten data-center availability.
- Calculate net impact. Include heat-pump electricity, pumping, backup systems, embodied construction emissions, refrigerants, and the fuel or electricity being displaced.
- Define verification. Install meters that distinguish heat generated, captured, exported, and actually consumed.
Common claims that need qualification
- “All electricity becomes usable heat.” Nearly all electricity becomes heat, but only part may be captured and economically delivered.
- “Waste heat is free.” The byproduct is available, but heat exchangers, pumps, heat pumps, storage, pipework, controls, and backup systems require capital and operating costs.
- “Heat recovery eliminates cooling.” The data center must still remove heat from IT equipment; recovery changes the destination.
- “Liquid cooling is always greener.” Its total impact depends on pumping, coolant, manufacturing, maintenance, electricity carbon intensity, and whether heat is actually reused.
- “A large data center can heat a city.” Only a compatible network with sufficient capacity, demand, temperature matching, and backup can use that output.
- “Heat pumps always improve efficiency.” Their electricity consumption and coefficient of performance must be included in the system calculation.
Where the model is heading
AI workloads are increasing rack power density and making liquid cooling more important in new construction. That creates an opportunity to design heat-recovery interfaces into the building from the start rather than attempting a difficult retrofit later.
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallFuture site decisions are therefore likely to consider more than electricity, fiber, land, and grid connection. The availability of nearby heat demand, district-energy infrastructure, storage sites, and suitable pipe routes can become part of the data-center business case.
Vendors such as Danfoss and Alfa Laval offer heat-recovery and heat-transfer equipment, while Schneider Electric and Motivair provide liquid-cooling and heat-rejection solutions. For major projects, however, the purchase is rarely a single piece of equipment: it is a coordinated engineering, construction, controls, utility, and operations project.
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