Britain’s network of abandoned coal mines is increasingly being viewed as a potential source of low-carbon heating, as energy developers, local authorities and researchers explore ways to harness warm water trapped underground in former mining workings.

The concept relies on extracting water that has accumulated in disused mines and using heat pump technology to transfer its thermal energy into buildings. While geothermal projects often require costly drilling and carry geological uncertainties, former coal mines provide existing underground infrastructure that can offer access to naturally warmed water.

According to researchers working in the field, mine water temperatures can reach approximately 40 degrees Celsius at depths of around one kilometre. Although those temperatures are lower than those typically associated with conventional geothermal systems, they remain high enough to support heating networks when combined with modern heat pump technologies.

The approach has attracted growing attention in the United Kingdom, where thousands of former coal mines remain beneath towns and cities that developed during the industrial era. Industry specialists say the concentration of former mining infrastructure beneath populated areas creates a potentially significant opportunity to supply heating close to where demand already exists.

Fleur Loveridge, Professor of Geo-Energy Engineering at the University of Leeds, said mine water projects can offer substantial benefits but also involve technical challenges. “The reward on offer is potentially greater but there’s a little more risk in getting there,” she said.

Researchers estimate that around 23,000 flooded coal mines exist across the UK. Many are located beneath or close to residential and commercial districts. According to figures cited by experts in the sector, approximately one-quarter of UK homes, along with a large number of businesses, are situated above or near disused coal mining workings.

That geographical overlap is central to the technology’s appeal. Unlike some renewable energy projects that require extensive transmission infrastructure, mine water heat systems can potentially be developed near existing communities, reducing the distance between energy production and consumption.

The north-east of England has emerged as one of the leading regions for deployment. In Gateshead, Britain’s largest operational mine water heat network supplies energy to a range of public and residential buildings. The network provides heating to Gateshead College, the Baltic Centre for Contemporary Art and approximately 350 social housing properties.

The project demonstrates how former industrial infrastructure can be repurposed to support contemporary energy needs. Operators and local authorities involved in the scheme are also examining opportunities for expansion. Current plans include extending the network to an additional 270 private homes as well as a conference centre and hotel.

The development has become one of the most closely watched examples of mine water heating in the UK because it provides practical evidence that the technology can function under British climatic and operating conditions. Energy researchers say such projects are important in assessing long-term performance, reliability and commercial viability.

The potential of mine water heating is not limited to Britain. Similar systems are operating elsewhere in Europe, particularly in regions with long mining histories. In the Dutch city of Heerlen, homes are connected to a district heating network that uses energy extracted from mine water. Local plans envision a substantial expansion of the system over the coming decades, with many thousands of additional dwellings expected to be connected.

Germany has also provided evidence of the technology’s practical application. In the town of Bad Ems, municipal buildings have been heated using mine water for several years. A study published in February examined the performance of the system and reported that the mine water supplying heat to the town hall maintained temperatures of approximately 25 degrees Celsius.

Researchers involved in that study described the resource as significantly underutilised. They concluded that the available thermal energy could support heating for a larger number of buildings than are currently connected to the system.

The European examples have attracted attention from policymakers and energy planners seeking alternatives to fossil-fuel-based heating systems. Heating remains one of the most difficult sectors to decarbonise because of the large energy requirements associated with residential, commercial and public buildings.

Mine water projects offer one possible pathway by reusing infrastructure that already exists underground. Former coal mines often extend across extensive areas and can contain large volumes of water that have gradually warmed through natural geothermal processes. Supporters of the technology argue that this combination of existing infrastructure and available thermal energy creates opportunities that may not require the same level of drilling associated with other geothermal developments.

However, experts note that each site presents unique geological and engineering conditions. Water quality, underground connectivity, pumping requirements and long-term maintenance considerations can vary substantially between locations. As a result, detailed site assessments remain essential before projects can proceed.

Despite those challenges, interest in mine water heating continues to grow as governments and energy providers seek ways to reduce carbon emissions while improving energy security. Existing projects in Britain, the Netherlands and Germany are increasingly being viewed as practical case studies for how former industrial assets can contribute to modern heating networks.

Loveridge said the Lanchester Wines installation in north-east England provides an important demonstration of the concept’s viability. “It does show that it works, and it works in UK conditions,” she said. “It’s great that they’re securing the future of it.”