County Durham is a large, predominantly rural local authority in North East England, with distinctive urban centres with concentrated heat demand. The region faces substantial decarbonisation challenges as it transitions away from natural gas heating while working towards its ambitious 2045 net zero target. Recognising these opportunities, City Science was commissioned by the Department of Energy Security and Net Zero (DESNZ) to conduct two Heat Network Delivery Unit (HNDU) feasibility studies. The study identified viable heat network schemes to support the county’s net zero target, enabling the council to move from exploration to action.
City Science Response
Review of Existing Studies: The work began with a literature review, identifying opportunities and constraints in past feasibility assessments. We integrated national heat network zoning model outputs (NMR4) and aligned them with local priorities to identify two areas of focus: Durham City and Newton Aycliffe.
Figure 1: Review of heat network focus areas, and their corresponding outputs from the National Model Run 4
Stakeholder Engagement: Collaborative engagement with local businesses and council departments was fundamental to designing networks responsive to real-world operational needs. This interaction allowed us to factor in social, economic, and environmental KPIs into the feasibility scenarios.
Low Carbon Heat Supply & Demand Profiling: We carried out a comprehensive review of viable low-carbon heat sources, identifying a wide range of options, including the selected technologies: Waste Heat from a biogas plant for Newton Aycliffe, and Deep Geothermal for Durham City.
Figure 2: Review of low-carbon heat source options
A hierarchical data strategy, prioritising actual consumption data, underpinned our demand analysis. The figure below shows our data strategy which enabled accurate load profiling and identification of anchor demand clusters.
Figure 3: Heat demand data hierarchy
Network Scenarios and Techno-Economic Modelling: Three to four heat network scenarios were created for each study area, aligning heat clusters with low-carbon heat sources. Alongside the scenarios, the study delivered detailed RIBA Stage 2 drawings and operational details, with all concept designs developed following the CIBSE Code of Practice CP1 to ensure technical compliance with industry standards.
The graphic below shows exemplary the heat network scenario for Durham City, created using our in-house GIS mapping tool Cadence.
Figure 4: Proposed heat network routing and building connections
We utilised our in-house techno-economic model to analyse cashflows, cost and risk, benchmarking each scenario against a counterfactual for comparative insight. For instance, the graphic below illustrates the domestic and commercial tariff structure considered in the analyses.
Figure 5: Heat tariff structure approach
Implementation Planning & Risk Assessment: Our final deliverables included a staged implementation roadmap with timelines, recommended funding pathways, and clear governance and ownership considerations. A detailed risk matrix was developed across all domains – technical, financial, operational – to support confident decision-making. The study concluded with clear guidance on preferred options, presenting both a feasible short-term delivery scheme and a vision for long-term expansion.
Figure 6: Proposed development timeline
Outcomes
The study identified potential schemes in Durham City and Newton Aycliffe. Both potential schemes demonstrate strong economic performance and significant carbon savings, highlighting district heating as the lowest-cost, low-carbon heating solution for the identified buildings.
The study was delivered on time and to budget, demonstrating City Science’s commitment to efficient and reliable project delivery. As a result of the feasibility study, Durham County Council is now equipped with a clear, evidence-based understanding of the viability of heat networks in the region. The study aligned fully with upcoming national heat zoning regulations and positions the council to take a leading role in regional low-carbon heat infrastructure.
The outputs will support informed decision making and provide a strong foundation for funding applications (e.g. Green Heat Network Fund).
Have a look our case study on Cadence: HNZ Durham – Case Study – Cadence
Client Testimonial
“We recently collaborated with City Science on an HNDU report, focusing on a highly specialised heat network that explored deep geothermal as a source of heat and power. City Science handled the project with exceptional professionalism and expertise, delivering precise economic modelling for the network. The team demonstrated remarkable attention to detail, engaging effectively with multiple council teams to foster support and ensure a comprehensive, whole-systems approach. The report was well written and the executive summary was detailed enough to provide a good overview, but was accessible for non-specialists to understand.”
Ellie Grimes (Net Zero Team Leader – Durham County Council)