District heating pipes carry hot water from one central source to warm many buildings at once; smart networks add sensors and AI demand response.
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District heating is a network of insulated pipes that carries hot water from one central source — a power plant, a waste incinerator, or a large heat pump — to warm many buildings at once, instead of each building burning fuel in its own boiler. The idea is simple: producing heat in bulk is usually cheaper and cleaner than doing it a thousand times over.
The smart-city angle is the data and control layer laid over the pipes. Sensors track flow, temperature and pressure so operators can find leaks and balance load, and AI can predict demand and shift when buildings draw heat — as HOFOR and Danfoss do with Copenhagen's Leanheat, trimming morning peaks. Heat that would otherwise be vented can be recovered or traded: Stockholm's Open District Heating lets data centres and supermarkets sell surplus heat into the grid, turning the network into a flexible part of the wider smart grid.
The honest catch is cost and lock-in. Laying citywide pipe runs into the hundreds of millions and pays back over decades, and a network is tied to whatever source it was built around — hard to change later — so it only pencils out at real density. And "smart" often means monitoring, not control: Milan hunts leaks by flying thermal cameras over its roughly 390 km network at night, yet real-time sensors and automated valves so far live in a single pilot.
Added 2026-08-06 · Part of the growing Smart City Glossary