Annual savings of up to £160k

Heat network losses reduced up to 43%

Maintenance frequency of dwellings reduced by 20%


The project is based in a residential development in south London, comprising approximately 962 dwellings across 19 sites. Each site consists of a series of low-rise blocks or townhouses. The heating and hot water for the network are supplied by a two-pipe communal heat network originating from a central plant room. The plant room houses a gas-fired CHP and three gas-fired boilers, which serve as the primary source of heat for most of the year. Each dwelling is equipped with an indirect Heat Interface Unit (HIU) that delivers instantaneous Domestic Hot Water (DHW) and provides space heating via radiators.


The development faced challenges with the plant performance, which resulted in increased customer complaints. The most common types of outages included boiler loss, leaks, pressurization unit faults, and other issues such as electrical faults, fire alarms, and part replacements. The top customer complaint category was supply issues, including insufficient hot water and space heating. The heat loss across the system was higher than expected for a well-performing heat network due to high network operating temperatures observed in the plant room and across the site.

FairHeat Solution

The Energy Service Company engaged with FairHeat’s specialist Operations team with the aim to improve the performance of the plant and better the consumers experience.

The project involved an assessment of the energy center, heat network distribution, and dwelling inspection. The energy center assessment included a review of all equipment, the hydraulic arrangement, and current performance. The heat network distribution inspection involved reviewing the installation and current performance, including the presence of any sub-optimal components. The dwelling inspection included a review of the installation and HIU performance during all modes of operation.

Three work packages were developed:

  1. Work Package 1: Improve the performance of heating systems in dwellings by recommissioning all HIUs. Minimise pump energy consumption and reduce boiler set points to lower network operating temperatures.
  2. Work Package 2: Includes the same set of improvement works as Work Package 1, but also proposes the installation of a jockey pump to further reduce pump energy consumption, and the re-routing of dosing pots to meet minimum turndown requirements.
  3. Work Package 3: Includes the same improvement works as Work Packages 1 and 2, with the added replacement of specific HIUs with high-performing instantaneous HIUs to improve performance and reduce network operating temperatures.


The optimisation project significantly enhanced the performance of the heat network, resulting in more reliable heating for residents and a 20% reduction in maintenance frequency across all dwellings. Notably, heat network losses were cut by up to 43%, and flow and return temperatures were lowered from 81/78 °C to 65/47.5 °C. The implementation of the three work packages led to substantial annual savings of up to £160k, with total cost reductions related to heat, electricity, carbon, overheating, and maintenance ranging from 16% to 30% depending on the work package. Overall, the project achieved significant improvements in efficiency, reliability, and cost-effectiveness.

Maintenance frequency of dwellings reduced by 20% across all work packages.

Flow and return temperatures reduced from 81/78 °C to 65/47.5 °C.

Heat network losses reduced by 24% (Work Package 1), 25% (Work Package 2), and 43% (Work Package 3).

Annual savings of up to £160k for costs associated with heat, electricity, carbon, overheating, and maintenance.

Total cost reduction (heat, electricity, carbon, overheating, and maintenance) is around 16% (annual saving £82k) for Work Package 1, 18% (annual saving £96k) for Work Package 2, 30% (annual saving £160k) for Work Package 3.


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