Engineering
Waste heat is a product
A data centre converts nearly every kilowatt-hour it draws into heat. For decades that heat went into the sky; German law now demands its reuse, and towns are learning that a computing building can be a heat plant with better economics. The numbers here are from our first site.
Every kilowatt-hour of compute becomes heat. Where it can go, what it displaces, and what a town gains from it.
The physics
Electricity that computes becomes heat, essentially all of it – a 2.5 MW IT load is a 2.5 MW heater running around the clock. It arrives as low-grade warmth, 30 to 40 degrees in the cooling circuit: too cool to feed a heating network directly, far too much to ignore.
Temperature and timing
District heating networks run hotter than a server outlet, so a heat pump has to lift the temperature – a machine whose economics work precisely because the source heat is free. The second problem is the calendar: in summer no network wants heat, so the building keeps its own guaranteed sink. Dry coolers stay, reuse comes on top.
What the law demands
The Energy Efficiency Act ties a reuse quota to the commissioning date: 10 percent from mid-2026, 15 from mid-2027, 20 from mid-2028. A building commissioned in early 2028 – ours – lands in the 15 percent tier. The quota is met with pipes and contracts, not certificates.
The Quedlinburg case
At the 3 MW expansion case our first building rejects about 21,900 MWh of heat a year. Quedlinburg already operates 9 km of district heating delivering roughly 43 GWh a year through 99 transfer stations – and the heating plant stands on the same street, with the nearest 175 connected homes 200 to 670 metres away. The 15 percent quota, about 3,285 MWh, equals roughly 7.6 percent of everything the town's network delivers in a year. The conversations with the network operator are ahead of us; the geometry is already on our side.
What makes a site heat-ready
Four things decide whether waste heat becomes a product or a press release: an existing network within pumping distance, a counterparty who operates it, a temperature the lift can bridge economically, and enough load on the network to absorb the heat in winter. That list is part of how we choose buildings – heat is a site-selection criterion, not an afterthought.
Sources
- 01Energieeffizienzgesetz (EnEfG), § 11 – waste heat obligations for data centres
- 02District heating network and Heizwerk Süderstadt: Stadtwerke Quedlinburg
- 03Bitkom, Data centres in Germany – market study
