NESO CMP405 Proposes Splitting TNUoS Year Round and Peak Security Locational Demand Signals to Reward Storage Import Location

SSE (proposer Damian Clough) submitted CUSC Modification CMP405 on 10 November 2022 proposing to separate the Year Round locational demand signal from the Peak Security locational demand signal within TNUoS demand tariffs, so that Storage assets importing outside Triad periods (e.g. during high wind generation) can be charged or rewarded based on the Year Round signal rather than having it floored/netted to zero as under current methodology.

Current TNUoS demand charging floors locational signals at £0/kWh and sums Peak Security and Year Round signals into a single Triad-based demand tariff, which the proposer argues removes any locational incentive for Storage to site near intermittent generation. Separating the signals could better align Storage siting with network investment needs, reduce constraint costs, and support net zero by enabling storage to absorb otherwise-curtailed low-carbon generation.

CMP405 is a structural network-charging reform targeting a specific market-design defect: the netting/flooring of two distinct locational demand signals (Peak Security vs Year Round) into one Triad-based TNUoS demand tariff, which the proposer contends eliminates any locational price signal for Storage to co-locate with intermittent generation. This is analogous to generation-side locational signals already in use (e.g. negative Generation Year Round tariffs in zones with excess intermittent capacity), but currently absent for demand-side Storage. The proposal is explicitly being run in parallel with, but not merged into, CMP393/CMP394 (which address Storage export TNUoS charging and Transmission Network needs), reflecting an intentional decomposition of Storage transmission-charging reform into import-side (CMP405) versus export-side (CMP393/CMP394) tracks. The proposer's own CUSC Charging Objectives assessment claims positive impacts on cost-reflectivity (Objective b) and alignment with Transmission Owner/ESO investment programmes such as the Network Options Assessment and pathfinders (Objective c), while flagging neutral impact on EU Electricity Regulation compliance and administrative efficiency. Critically, both the Workgroup governance timetable and the 1 April 2024 implementation date are explicitly marked 'TBC' and 'linked to CMP393/CMP394,' indicating that CMP405's procedural and delivery timeline is contingent on, and likely paced by, the parallel Storage TNUoS modifications rather than proceeding independently. Given the 2022 submission date and the source's much later publication/snapshot date, the originally stated 1 April 2024 implementation target should be treated as a stale planning marker rather than a confirmed delivery date; no subsequent Workgroup Report, Code Administrator Consultation outcome, or Ofgem decision is evidenced in this source, so the proposal remains at the governance-route decision stage described in the Status Summary.

CUSC (Connection and Use of System Code) Modification Proposal process; potential linkage to Electricity Balancing Guideline (EU Regulation 2017/2195) Article 18 consultation requirement if Exhibit Y clauses amended

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Primary sources