NESO awards first contracts under the Mid-Term (Y-1) Stability Market

• Today, NESO is proud to announce the award of 5 contracts for the provision of 5 GVAs of inertia between October 2025 and September 2026, under the Mid-Term (Y-1) Stability Market.

In 2021 NESO launched the Stability Market Design innovation project to explore the design required to create enduring stability markets.  The project concluded with the intention to develop stability services across several timescales.

As NESO transitions from stability pathfinders to enduring services and markets for stability products the creation of new markets has become a necessary evolution for the use of stability services to support the long-term operation and resilience of the electricity system.

Building on innovation work delivered in 2021, NESO has begun the process of delivering dedicated markets for stability services over short to long-term time horizons.

These new markets are broken down as follows:

• Long-Term (Y-4), providing a four year delivery window
• Mid-Term (Y-1), for delivery across a single year 
• Short-Term (D-1) for delivery on a rolling day ahead basis

Last year, NESO launched the first tender round under the Mid-Term (Y-1) Market to procure stability services. The Mid-Term (Y-1) Market was launched as a priority to access inertia capability from existing assets on a high-availability basis. Through annual contracts, this market provides revenue certainty for market participants whilst reducing risk for NESO as periods of low inertia become more frequent and unpredictable. 

Having now concluded a rigorous tender assessment process, NESO can announce the award of contracts worth an anticipated £25.4 million to 5 providers to deliver 5 GVA.s of inertia for the Mid-Term (Y-1)’s inaugural delivery year between October 2025 and September 2026. The full tender results can be found on the Mid-Term (Y-1) Stability page.

• The first contracts to be awarded under the Mid-Term (Y-1) Stability Market will deliver an anticipated consumer saving of £47.3 million

As outlined in our Frequency Risk and Control Report, NESO must operate the power system above the minimum target inertia threshold (currently 120GVAs) at all times. The award of these contracts will help contribute to the stability of the GB power system by providing cost-effective, zero-carbon solutions which can be utilised to increase system inertia during periods of shortfall. 

The expression of interest and consultation phase for the Mid-Term (Y-1) Market Tender Round 2 (Delivery Year 2026 – 2027) is now open, further details can be found here.