District heating and cooling networks: Efficiency and losses

Pipes that leak heat every hour of the year

What this tab covers How much energy is lost while it moves and while it waits in storage or transit, and how much energy the transport itself consumes, in per cent.

Heat networks lose energy continuously through the pipe walls, so losses are counted as a share of the heat sent out over a year rather than per kilometre. Typical annual losses are about 8 to 15% in western and northern Europe and 15 to 25% in older eastern networks; a survey of some 800 systems found a mean of about 13%, and sparse rural networks can lose over 40%. Pumping uses about 1% of the heat delivered as electricity.

Chart: Efficiency ranges

Lost in transit Used to drive transport

Losses by measure

Measure	Range	Type	What is measured
Distribution heat loss, western and northern Europe	8 to 15%²	Lost in transit	Share of heat supplied to the network that is lost from the pipes over a year
Distribution heat loss, eastern Europe	15 to 25%²	Lost in transit	Share of heat supplied that is lost over a year, older high-temperature networks
Survey of about 800 systems in five countries (2014)	11 to 24%²¹	Lost in transit	National median annual heat loss (Switzerland 11%, Denmark 24%); overall mean about 13% at 1.8 MWh per metre of pipe per year
Veolia networks versus European range (company data)	10 to 30%¹⁹	Lost in transit	Losses implied by network efficiencies of 70 to 90% across Europe (Veolia average 88%), calculated as 100 minus efficiency
Swiss reference network (DN 80)	10.5%⁶	Lost in transit	Share of heat lost in distribution over a year (model)
UK SAP default, code-compliant network without measured data	33%³	Lost in transit	Share of generated heat lost implied by the default distribution loss factor of 1.5 (calculated: 1 - 1/1.5); a non-compliant network gets 2.0, or 50%
Pumping electricity	1%³	Used to drive transport	Electricity added as a share of space and water heating demand (UK SAP default)
Bare 8-inch steam line at 150 psig	1480 MWh per 100 m per year⁷	Lost in transit	Heat lost from uninsulated horizontal steel pipe in 24 C still air over 8,760 hours (calculated from 1,540 MMBtu per 100 ft); insulation typically cuts this by about 90%

Holding periods and inventory

Measure	Value
Time in transit	Water circulates continuously, so there is no separate stock; pipe losses run all 8,760 hours of the year whether or not heat is sold⁷
Effect of lower temperatures	Running the same pipes at 55/25 C instead of 80/45 C would cut heat loss by about 43%²
Effect of heat density	Losses rise as heat sold per metre of pipe falls, and at a given density they can differ by more than a factor of three between networks²¹

Because losses depend on temperature and pipe surface rather than on how much heat is sold, they are worst in summer and on thinly loaded networks, which is why planners use heat density (heat sold per metre of pipe) as the test of viability. Published figures are not fully comparable: some are measured, some modelled, and the UK SAP default is deliberately pessimistic for networks without data. Steam is far lossier than hot water when pipes are bare or traps fail, which is why insulation and trap maintenance are the main efficiency measures in industry. District cooling plants in the Gulf run at about 0.8 to 1.05 kW of electricity per refrigeration ton (3.5 kW of cooling), a coefficient of performance of about 3.3 to 4.4 (calculated).

Sources

Distribution technologies for low-temperature district heating (LTDH) European Commission, Smart Cities Marketplace, 2019
SAP 10.2 Appendix C: Community heating, including heat networks (draft) UK Government / BRE, 2021
Sensitivity of System Design on Heat Distribution Cost in District Heating (Nussbaumer and Thalmann) IEA Bioenergy Task 32 / Verenum, 2014
Steam Tip Sheet 2: Insulate Steam Distribution and Condensate Return Lines US Department of Energy, 2012
Veolia ambitions to lead European district heating by 2030 and launches new offer in urban energy (company data) Veolia, 2025
Status Report on District Heating Systems in IEA Countries (Nussbaumer and Thalmann) IEA Bioenergy Task 32 / Swiss Federal Office of Energy / Verenum, 2014