Ofgem is consulting on a proposed Oversubscribed Technologies Commitment Fee that would require battery storage projects to post financial security to hold their place in Great Britain's grid connection queue. The measure, raised as CUSC modification CMP470 by developer Field Energy, targets technologies whose queued capacity far exceeds clean power targets. Ofgem says it is minded to approve the proposal, though no final decision has been made.
What CMP470 Would Introduce
CMP470 is a Connection and Use of System Code modification proposal that would introduce an Oversubscribed Technologies Commitment Fee for certain oversubscribed technology generation projects connecting to the Great Britain transmission or distribution system. It is intended to set a floor on the amount of security such projects must provide to NESO in order to obtain a connection, and also to set a floor for the cancellation charge.
The modification was raised on 20 March 2026 by Field Energy and has been granted urgent progression status by Ofgem. The fee would be applied through the existing Cancellation Charge and Cancellation Charge Secured Amount framework, with amounts falling below the floor increased to the applicable minimum through the biannual cancellation charge process. As is already the case, securities posted are returned where a project proceeds to connection.
Why BESS Oversupply Prompted the Change
Following the TMO4+ connections reform package, NESO protections mean that for certain technologies the number of projects qualifying for Gate 2 offers significantly exceeds Clean Power 2030 capacity targets, with battery energy storage systems particularly affected. The sources report around 90GW of operational and Gate 2 BESS capacity against an estimated CP30 requirement of around 29GW by 2035.
NESO cleared 40% of grid-level battery capacity from the queue, yet 83GW remains prioritised alongside 7GW of operating capacity. If every project with a connection offer were built, capacity would be 14.8GW above NESO's 24GW estimate for the 2030 clean power target and 61.7GW above the 29GW projected as required by 2035.
The proposer argues that this excess undermines connections reform, because NESO and transmission owners must plan network infrastructure for a significant number of projects that will never be built, delaying connections for all technologies. Ofgem's provisional assessment is that the current level of oversubscription represents a material defect and that intervention is justified.
How the Escalating Fee Would Work
The fee would be triggered when total operational and Gate 2 capacity for a technology exceeds the relevant capacity target by more than 50%, provided that the capacity target exceeds 5GW. The initial floor would be set at £3,000 per MW upon first activation, applying for the first six-monthly period.
If oversubscription does not reduce by at least 25% in each subsequent six-monthly period, the floor would rise initially to £5,000 per MW and thereafter in £5,000 per MW increments until it reaches a cap of £25,000 per MW. The mechanism would be disapplied once oversubscription falls below 25%.
The fee would apply to all projects of the relevant oversubscribed technology holding a Gate 2 offer, up until energisation, including co-located projects. There would be an exemption for co-located projects where the oversubscribed technology connects after the other technology, does not increase Transmission Entry Capacity and has minimal network impact.
Consultation, Timing and Possible Changes
Ofgem is inviting industry stakeholders to comment on whether introducing a new fee structure is justified, how impact assessment should work and any implementation concerns, with responses due by 1 October. Possible modifications include capping the commitment fee at a project's maximum existing security exposure, removing the fee once a project begins construction, and removing an exemption for certain co-located projects.
Ofgem's minded-to position is to approve the proposed solution set out above, but it has not made its final decision, and the CMP470 workgroup also developed several alternative proposals. The measure would be introduced via a modification of Great Britain's connection and use of system code and would likely come into force in July 2027.
Key Takeaways
Ofgem is consulting on an Oversubscribed Technologies Commitment Fee proposed as CUSC modification CMP470 by Field Energy in March 2026.
The fee would start at £3,000 per MW and could rise in £5,000 per MW steps to a cap of £25,000 per MW while oversubscription persists.
Around 90GW of operational and Gate 2 BESS capacity is queued against an estimated CP30 requirement of around 29GW by 2035.
Ofgem is minded to approve the proposal, with implementation likely in July 2027, but no final decision has been made.
Sources