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District heat network efficiency

Overall losses from district heat networks can be vary significantly between sites, available evidence suggests that the losses can be from under 15% to well over 30%.

Coil of district heating pipe

As well as the type of pipe and the quality of installation the following factors influence efficiency:

  • Length of network

The most basic requirement is to minimise the length of the network, based upon the density of development it is designed to serve. Shorter networks will be lower in cost and minimise heat losses.

  • Pipe sizing

If the pipe is oversized then heat losses will be higher and build costs will be higher than necessary.  This may arise as a result of over estimates of peak heat demands.

  • Operating temperatures and controls

Although lower operating temperatures (the average of flow and return temperatures over the year) will lead to lower heat losses, a smaller temperature difference between flow and return at peak design conditions will lead to higher heat losses for the same mean temperature as the pipes will need to be larger. A network designed for 70 °C/50 °C will have higher heat losses than one designed for 80 °C/40 °C especially if the 80 °C temperature is only used at peak times.

Lower operating temperatures and lower return temperatures can be achieved through appropriate building services design, i.e. by using larger heat emitters and selecting suitable approaches to controls.