What is a heat network?

A heat network is the system of insulated pipes which transports heat from a source (or multiple sources) to more than one end user. The UK government has stated that heat networks will be used more frequently to heat our homes and businesses. In short, heat networks form part of new energy infrastruture, vital in supporting the move to a low carbon energy system.

They are natural monopolies which means that one organisation is the supplier for all properties on a single heat network.

There are two types of heat networks: district heating and communal heating.

• Communal heat network: Communal heating is the supply of heat and hot water, from a source usually known as the energy centre, to a number of customers within one building only. The energy centre often consists of a large boiler in the basement of a building with the heat and hot water distributed through the building via a series of pipes.

 

• District heat network: District heating involves a local energy centre that supplies heat and hot water to customers in more than one building. District heating networks can range in size from a few hundred metres supplying just a few homes to several kilometres of pipe supplying heat and hot water to multiple buildings in a development.

 

According to market data collected by government, most heat networks are actually communal heat networks (85%).

Some new heat networks are built for large projects which are completed in stages. This might mean that some residents will move in to their homes before others are built, which will be joined to the heat network when completed.

Who would be the heat network supplier?

Heat Trust defines the heat network supplier as the organisation that is contracted to provide heating and/ or hot water to each property – they would provide the Heat Supply Agreement (or customer charter) to each occupant on the heat network.

The type of organisations that fulfil this role can vary network to network. For example, this could be:

• A dedicated heat network company (energy supply company or 'ESCO')
• The property developer
• A housing association
• A local authority
• A community organisation
• A management company
• A company set-up by the freeholder to operate the network

All heat network suppliers that have registered one or more heat networks with Heat Trust can be found here.

Heat Interface Units (HIUs)

Some heat networks will include a heat interface unit within each property.

A heat interface unit (HIU) is the bridge between the communal or development-wide heat network and the individual property. It is a unit that brings hot water to and from the main heat network into each property.

There are two main types of HIU.

1. Heat-only HIUs – these are used on heat networks that only provide space heating to properties connected to the heat networks. The hot water is typically provided by an electric immersion heater and hot water tank.
2. Heat and hot water HIU – these are used on heat networks that provide both space heating and hot water to each property connected to the heat network.

There is an industry standard for the performance of HIUs. More information can be found on the BESA website here: https://www.thebesa.com/heating-interface-units

Where are heat networks in the UK?

The database of registered heat networks in the UK[1], recorded that in 2015 there were just under 14,000 heat networks. Of these around 2,000 were district heating and 12,000 were communal[2]. These served nearly 480,000 customers, providing around 2% of the UK buildings heat demand[3].

Heat networks require a certain density of heat demand in order to be economic. The geographical distribution therefore reflects that heat networks, and particularly district heating networks, are located in urban areas, new build developments and some rural areas.

BEIS map of heat network distribution in the UK by local authority.

Nearly 12,000 of all heat networks in the UK were in England (86%). 6% were in Scotland, 2% in Wales and 0.6% in Northern Ireland.

29% of heat networks were in London, and a further 14% in the South-East of England. Others were concentrated around Manchester, Birmingham, Newcastle, Sheffield, Bristol and Glasgow. Belfast had the highest proportion of heat networks compared to other regions in Northern Ireland.

Over 75,000 buildings were connected to heat networks. 80% of heat networks were connected to residential buildings. An even higher proportion of final customers were residential (92%)[4]. This reflects the higher proportion of communal heating networks, which are generally apartment blocks. 9% of heat networks were connected to education buildings, and 7% were commercial.

The majority of heat networks supplied both space heating and hot water (70%), with only 8% supplying cooling as well.

Only 28% of final customers had meters. Scotland had the highest proportion of final customers with meters, at 40%, and Wales had the lowest (4%).

Of those who responded to the question (12,000), 32% billed their customers annually, 25% monthly, 16% quarterly and 27% responded with ‘other’, which could include Pay As You Go (PAYG).

Most networks (90%) used gas as their primary fuel source. The next most widely used fuel source was electricity (5%) followed by bioenergy and waste (2%). See our sources of heat page for more information and some examples.

To find out which heat networks are registered with Heat Trust, click here. 

[1]https://assets.publishing.service.gov.uk/Government/uploads/system/uploads/attachment_data/file/712370/Energy_Trends_article_on_heat_networks_revised.pdf

[2] https://www.heattrust.org/images/docs/Scheme_Information_Sheet_Aug_2023.pdf

[3]https://assets.publishing.service.gov.uk/media/5b55965740f0b6338218d6a4/heat_networks_final_report.pdf

[4] https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/712370/Energy_Trends_article_on_heat_networks_revised.pdf

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