The Electricity System Operator (ESO) launched an interim Constraint Management Intertrip Service (CMIS) for the EC5 region in February 2024, with an enduring service to follow from April 20251. The detail appears in the ESO's first Annual Balancing Cost Report, published in May 2024, which states: "Interim CMIS EC5 service launched February 2024 with Enduring Service from April 2025"1.
The report gives no further description of the service, the size of the region it covers, the number of parties involved or the cost of the interim arrangement. Those points have not been reported1.
The launch sits within a wider set of ESO commercial mechanisms intended to hold down the cost of balancing the grid. The report records that in November 2023 procurement of Dynamic Containment, Dynamic Moderation and Dynamic Regulation moved to the Enduring Auction Capability platform, which offered splitting, co-optimisation and negative pricing, leading to greater efficiency and reduced prices1. It also notes that the Local Constraint Market has been open regularly since December 2023, and that at the start of 2024 the ESO issued connection contracts with accelerated connection dates for 10 GW of battery energy storage1.
Balancing costs overall fell sharply in the year. The report puts total balancing spend at £2.4 bn in 2023/24 against £4.1 bn in 2022/23, with net balancing volumes down to 10.8 TWh from a 2020/21 peak of 21.4 TWh1. Thermal constraint costs were the largest single component, at 40 per cent of balancing costs in 2023/24 against 36 per cent in 2022/231. Reserve volumes fell from 5.7 TWh in 2022/23 to 4.8 TWh in 2023/241.
"Thermal constraint costs are currently the most significant component of balancing costs, contributing to 40% in 2023/24 compared to 36% in 2022/23."
The report states that balancing costs are projected to rise out to 2030, with constraints the main driver, and that ESO initiatives create savings worth around £18bn before 20301. It describes the projections as a best view of trends rather than a forecast, and says they depend heavily on wholesale energy prices1.
Why it matters for households
Balancing is the work of matching generation to demand second by second and managing the physical limits of the network, and its cost reaches households through the Balancing Services Use of System charge. The report states that in 2023/24 BSUoS contributed about 4 per cent of electricity bills for an average domestic consumer, roughly £4 a month on a typical domestic electricity bill1. That figure is a share of the bill, so it moves with both the total cost of balancing and the size of the bill itself.
Constraint costs arise where the network cannot carry power from where it is generated to where it is needed, and the report says volumes of thermal constraints remain high and are expected to increase as the network becomes more congested1. Services such as CMIS act on those limits directly, which is why their cost and coverage feed into the balancing component of a bill. The report also notes that new network can take up to 14 years to build, far longer than connecting a new renewable generator, producing a lag between new generation connecting and the infrastructure to carry its output1. For a household, that lag is the mechanism by which constraint costs persist even as more low carbon generation connects. The national supply hub sets out how the system is balanced, and the balancing services and frequency response page covers the services that do it. The ESO's own role is described under NESO.
What happens next
The enduring CMIS EC5 service is due from April 20251. The report also points to the second Review of Electricity Market Arrangements consultation, published on 12 March 2024, which seeks feedback on options with the potential to reduce thermal constraint costs1. No further dates for the CMIS service have been reported1.
Sources1 cited
- PowerPoint Presentation, neso.energy