What is district heating, and why is it more efficient?
A network of insulated pipes carrying hot water from a central source to many buildings, replacing individual boilers. It is efficient not because the heat is better but because scale unlocks heat sources no single building could ever use.
The basic arrangement. A central energy centre heats water and circulates it through buried, heavily insulated flow and return pipes. Each building has a heat interchange unit rather than a boiler — smaller, quieter, with no combustion, no flue and no annual safety check.
Why it enables better sources. This is the real argument:
Waste heat. Data centres, industrial processes, sewage works, underground railways and power stations all reject enormous quantities of low-grade heat. It is far too diffuse to be worth capturing for one building and entirely worth capturing for ten thousand. Using heat that is currently thrown away is the single strongest case for these networks.
Large heat pumps, drawing from a river, the sea, mine water or the ground at a scale and efficiency no domestic unit can match.
Energy from waste, geothermal, and large thermal stores that let heat be generated when electricity is cheap and delivered later — a genuinely valuable form of energy storage.
Fuel switching without touching buildings. Change the source at the energy centre and every connected home decarbonises at once, with no internal works.
The real drawbacks:
Cost and disruption. Digging pipes through a city is expensive and slow, so networks need high heat density to be viable — dense urban areas, not suburbs.
Monopoly. A connected customer cannot switch supplier, which is why consumer protection and price regulation for heat networks have become a live issue after complaints about pricing and reliability.
Distribution losses, which rise if networks run hotter than necessary — modern low-temperature networks lose far less.
Older networks ran on gas combined heat and power and are not automatically low-carbon; the carbon case depends entirely on the source.
Denmark and Sweden heat a majority of buildings this way, which demonstrates that the obstacle is not technical.