SSEN Transmission delivered £296 million in savings last year for electricity consumers by reducing constraint costs on the national electricity transmission network.
- £296 million savings for electricity consumers in the 2025-26 financial year, driven by reduced constraint costs
- Innovative network solutions in Aberdeenshire reduce costs while supporting major infrastructure upgrades
- Grid investment to unlock more clean power and cut long-term costs
The saving, confirmed by the National Energy System Operator (NESO), reflects SSEN Transmission’s work under the System Operator: Transmission Owner (SO:TO) Optimisation incentive, which encourages innovative solutions to reduce constraint costs while maintaining a secure and reliable network.
Constraint costs occur when the electricity network cannot carry all available power, meaning some generation, often renewable energy such as wind, must be reduced or switched off. This can happen when generation exceeds available network capacity or during outages for essential upgrade or maintenance works, with the costs ultimately passed on to electricity bill payers.
Investing in the grid is key to addressing this challenge by removing bottlenecks and creating capacity for more clean power. Increasing network capacity will allow more renewable energy to flow from where it is generated to where it is needed, reducing the need for generators to turn down or switch off and helping to remove constraint costs over the long term.
By identifying and delivering targeted engineering solutions, SSEN Transmission is reducing the need for these constraints now, while investing in network upgrades to reduce them further in the future.
One recent example is at Fetteresso substation in Aberdeenshire, where SSEN Transmission has introduced temporary by-pass infrastructure to support a major upgrade of the site and the connecting overhead power lines.
The Fetteresso 400kV upgrade project includes upgrading the existing substation from 275kV to 400kV, increasing network capacity and enabling more renewable electricity to be transported. Construction is currently taking place within the existing site boundary.
During these works, maintaining network capacity is critical to avoid increased constraint costs. Without intervention, long-term outages on key transmission circuits would reduce the ability to move electricity across the grid, leading to higher levels of constrained generation.
To address this, SSEN Transmission installed temporary by-passes that allow key 275kV circuits between Kintore, Fetteresso and Alyth to remain in service while upgrade works are carried out. This approach reduces disruption and avoids significant generation constraint costs.
David McKay, Network Director at SSEN Transmission, said:
“Reducing constraint costs is an important part of delivering a fair and efficient electricity system for consumers. The National Energy System Operator estimates that our interventions have delivered almost £300m of savings for consumers in the last financial year. This reflects the practical steps we are taking, in collaboration with NESO, to manage the network more efficiently whilst building the infrastructure necessary for the future.
“By working closely with NESO and taking an innovative approach to how we plan and deliver network upgrades, we are reducing constraint costs today while helping to unlock more clean power over time. Through continued investment in the network, we are removing bottlenecks, enabling more low-carbon generation to connect, and supporting energy security, reliability and affordability for consumers.”
The work at Fetteresso is one example of how the SO:TO Optimisation incentive supports collaboration between transmission owners and NESO, enabling changes that deliver clear benefits to consumers while protecting value through strict regulatory oversight. As further solutions are identified and delivered, additional savings for consumers are expected in future years.
SSEN Transmission is progressing its £29 billion investment in new and upgraded infrastructure across the north of Scotland. By expanding the grid at pace and scale, the programme will increase capacity, alleviate constraints and unlock more homegrown renewable energy. This will reduce reliance on volatile global fuel markets and strengthen energy security across Great Britain.