# Heat Reuse Every watt a data center consumes leaves the building as heat, and heat is something people pay for. Reuse means capturing it at a temperature somebody wants and delivering it to them, so that the facility's largest waste product becomes a local utility. It is the most direct way a compute campus can make itself materially useful to the town it sits in. > [!note] The one-sentence version > A data center is a furnace that happens to compute; the question is whether anyone nearby is cold. ## Why it has become practical Air cooling delivered heat spread thinly through large volumes of warm air, at a temperature too low to be useful for much. Liquid cooling changed the arithmetic. A cold plate can capture heat into water at temperatures well above what an air coil needs, and the warmer the capture, the more uses the heat has: the water arrives concentrated, in a pipe, at a temperature a heat network can work with. Liquid cooling made the facility's heat a product rather than a nuisance, and that is a genuine change of category. ## Prerequisites - **Grade of heat:** its temperature, which determines what it can serve. Water in the thirties of degrees Celsius suits low-temperature district networks, aquaculture, and greenhouses; raising it with a heat pump brings it to the fifties and above for conventional space heating and domestic hot water. - **Heat pump:** a device that moves heat from a lower temperature to a higher one using electricity, with a coefficient of performance several times one, which is what makes upgrading the heat affordable. - **District heating network:** piped hot water serving many buildings from a central source; the ideal customer because it has year-round demand and the pipes already exist. - **Load match:** the heat must be wanted when it is produced. A data center's output is constant; space heating demand is seasonal, which is why the best customers have steady needs. - **Proximity:** hot water loses value with distance; the economics are governed by how far the pipe has to run. - **Dual rejection:** the facility retains conventional heat rejection, because it cannot depend on a customer to take the heat at every moment. ## How it works The facility's warm return water, having collected heat from the cold plates, is routed through a heat exchanger that transfers it into the customer's loop rather than into the cooling plant. Where the customer requires higher temperatures, a heat pump raises the grade on the way. The facility's own plant remains in place and takes whatever the customer does not want, so the computing load is never hostage to the heat market. Metering on both sides establishes what was delivered, and the commercial arrangement runs from free delivery, which still saves the operator rejection energy, to a priced supply contract. ## Where it has worked and what it needs Established practice exists at scale in northern Europe, where dense district heating networks, cold winters, and policy support align, and facilities there supply heat to thousands of homes. In the United States the conditions are rarer: district heating is concentrated in a few cities and university and hospital campuses, and much new compute is built where land and power are available rather than where heat networks are. The practical American opportunities are therefore specific and real rather than universal: campuses with existing hot-water loops, industrial neighbors with process heat demand, greenhouses and indoor agriculture, aquaculture, swimming pools and municipal buildings, and new residential development planned alongside a campus from the start. The deciding factor is almost always whether somebody thought about it before the site was laid out, because retrofitting a pipe route is far harder than reserving one. ## Stack position - **Upstream:** liquid capture temperature, which sets the grade available. - **Downstream:** the heat customer, and the facility's remaining rejection load. - **Function and vendor:** optional and valuable; the engineering is standard district-energy practice. - **Degraded case:** the heat goes to the sky, as it has always done, and the energy spent making it is simply discarded. ## Relationships - **enabled by:** [[wiki/Direct-to-Chip Liquid Cooling|Direct-to-Chip Liquid Cooling]] · [[wiki/Chilled Water Plant|Chilled Water Plant]] - **reduces:** [[wiki/Cooling Tower|Cooling Tower]] load · [[wiki/Data Center Water Use|Data Center Water Use]] - **planned through:** [[wiki/Data Center Siting|Data Center Siting]] · [[wiki/Community Benefit Agreement|Community Benefit Agreement]] - **community context:** [[wiki/What a Data Center Gives Back|What a Data Center Gives Back]] - **source articles:** [[articles/Vertically Integrating an AI Superpower from AI Factory to Citizen|Vertically Integrating an AI Superpower from AI Factory to Citizen]] · [[articles/The Gigawatt Is the New Measure of War|The Gigawatt Is the New Measure of War]] - **collection route:** [[collections/American Infrastructure|American Infrastructure]] · [[collections/American|American Collection]] ## Evidence posture - **Established:** the dependence of reuse value on capture temperature; heat pumps upgrading low-grade heat with a coefficient of performance several times one; district heating as the model customer; the requirement to retain conventional rejection; operating data center heat supply to district networks in northern Europe. - **Established:** limited district heating coverage in the United States relative to northern Europe, concentrated in specific cities and institutional campuses. - **Plausible:** widespread American reuse through greenhouses, industrial neighbors, and co-planned development; individual projects exist and a general pattern remains to be demonstrated. ## Sources - District energy and data center heat recovery engineering practice and operating projects, as reviewed October 2026.