Energy Systems Catapult, commissioned by National Grid Electricity Transmission (NGET), led a pioneering study to assess the whole system impacts on Great Britain’s electricity transmission infrastructure of having nuclear reactors produce heat and power – a process known as cogeneration.

With the UK targeting 24 GW of nuclear capacity by 2050, the project explored how small modular reactors (SMRs) and advanced modular reactors (AMRs) could deliver both heat and power, alleviating grid stress, enhancing flexibility and operability, and supporting Net Zero.

Through stakeholder engagement, whole-system modelling, and network analysis, we identified six major opportunities and five critical risks.

The findings provide actionable insights for planning, resilience, and innovation as the UK transitions to a decarbonised energy system.

Our study shows nuclear co-generation could provide:

• 4.2 GW of additional firm capacity by curtailing heat loads during extreme stress events
• Heat to 40% of heat networks by 2050, reducing reliance on electrified heating
• A 1.6 GW reduction in power flows across the North-South boundary

The challenge

The UK’s civil nuclear fleet is ageing, with most advanced gas-cooled reactors scheduled for decommissioning by 2030. While large reactors like Hinkley Point C and Sizewell C will add capacity, the next generation of SMRs and AMRs promises flexibility and cogeneration capabilities – producing electricity and heat for direct air capture, industrial processes, hydrogen production and district heating.

However, this innovation brings uncertainty. How will cogeneration affect transmission operability, reinforcement needs, and resilience? Without clear insights, NGET risks making sub-optimal investment decisions, potentially locking in unnecessary costs or missing opportunities to reduce congestion and improve system stability.

The stakes are high: poorly coordinated deployment could undermine decarbonisation goals, increase network stress, and limit the benefits of nuclear cogeneration. This project closes that knowledge gap by providing evidence-based recommendations for strategic planning.

The solution

Energy Systems Catapult adopted a whole-system perspective, combining advanced modelling with stakeholder engagement:

• Whole system modelling: Using the Catapult’s Energy Systems Modelling Environment (ESME), nine reactor technologies were characterised, and five scenarios developed to explore nuclear cogeneration’s role in future energy systems.
• Network analysis: Outputs from ESME informed power flow and operability analyses using NESO’s 36-bus transmission model in DIgSILENT PowerFactory. Scenarios tested impacts on boundary flows, voltage, fault level and flexibility services.
• Stakeholder engagement: Interviews with industry, academia and government highlighted barriers linked to business models, regulatory hurdles and supply chain constraints.
• Insights: Eight cogeneration site configurations were assessed for flexibility potential, resilience during extreme events, and interaction with heat networks.

This integrated approach ensured recommendations were grounded in technical evidence and aligned with emerging strategic planning frameworks like Centralised Strategic Network Plan (CSNP) and Strategic Spatial Energy Planning (SSEP).

The impact

The study identified six key opportunities for nuclear cogeneration:

• reducing north-south power transfers
• improving system operability
• providing new source of flexibility
• enhancing resilience during extreme events
• supporting heat networks
• enabling potential future black start capability.

For example, we found that high uptake scenarios could cut boundary flows by up to 1.6 GW, potentially reducing the need for costly reinforcement of the grid.

Conversely, five major risks were flagged, including:

• sub-optimal network reinforcement decisions
• misalignment between strategic planning and investment processes
• nuclear cogeneration fails to deliver system benefits
• elevated fault levels and voltage compliance
• a failure to deploy SMRs/AMRs

These insights inform NGET’s future investment decisions, helping it plan more adaptively, ensuring infrastructure planning reflects evolving energy demand and the potential from new generation technologies.

The findings position nuclear cogeneration as a strategic enabler for Net Zero– if deployment is coordinated, risks are mitigated and innovation is embraced.

What’s next?

Nuclear cogeneration offers a transformative opportunity for the UK’s energy system. However as SMR and AMR development gathers pace, early, coordinated action will be essential to maximise benefits and avoid costly misalignment.

You can read the full report below and contact us directly to explore how Energy Systems Catapult can help you unlock innovation and accelerate the journey to Net Zero. Click on the ‘get in touch’ button below to start a conversation and take the next step.