CMP398 and CMP412 Authority Decision

What changed

Ofgem approved CMP398 and CMP412 on 29 February 2024, both CUSC modifications consequential to Grid Code Modification GC0156 (approved 5 February 2024). GC0156 established the Electricity System Restoration Standard — the replacement for the old Black Start framework — and imposed a new obligation on all CUSC parties who do not hold a Restoration Services contract with the ESO: they must maintain 72 hours of onsite fuel or energy resilience for their plant and apparatus. CMP398 creates the cost recovery mechanism within the CUSC for meeting that obligation. CMP412 makes a consequential amendment to Section 14 of the CUSC to facilitate CMP398's implementation.

The practical effect: generators and other transmission-connected parties who were previously outside the Restoration framework now have a mandatory resilience requirement — and a route to recover the costs of complying with it.

What this means in practice

Who is affected. Every CUSC party connected to the transmission network that does not already have a Restoration Services contract with the ESO. That captures the large majority of transmission-connected generators and demand users. Parties already contracted for Restoration Services are unaffected — they were already required to maintain resilience capability and are compensated through their contracts.

The obligation. 72-hour onsite resilience is not trivial. For a gas-fired generator, it means either fuel oil backup storage or contractual arrangements for onsite gas that can sustain operations for three full days without grid supply. For battery storage, pumped hydro, and interconnectors, the specific compliance requirements depend on their technology — but the principle is the same: if the system goes down, your plant must be able to survive and potentially contribute to restoration without relying on external supply for 72 hours.

The cost recovery mechanism. CMP398 establishes a route for affected parties to recover the costs of meeting this new obligation. The costs flow through TNUoS charges — meaning they are ultimately socialised across all transmission network users. This is the standard pattern for system security costs: impose an obligation for system resilience, then recover the costs through use-of-system charges.

The cost magnitude. The source documents do not specify the total cost. But the population of affected parties is large (hundreds of transmission-connected sites), and 72-hour resilience retrofitting is not cheap — particularly for plant that was designed without it. The per-site cost depends heavily on technology type and existing fuel storage arrangements. Gas plant with existing distillate backup tanks may already comply or need minimal upgrades. Plant without onsite fuel storage faces a capital investment.

The distributional effect. Costs recovered through TNUoS are split between generators and demand according to the prevailing charging methodology. Generators currently pay roughly 15-20% of TNUoS; demand pays the rest. So while generators bear the resilience obligation, most of the cost recovery falls on the demand side — which means suppliers and ultimately consumers.

What happens next

Implementation. CMP398 and CMP412 take effect alongside GC0156. The ESO is responsible for implementing the CUSC changes and incorporating the cost recovery mechanism into the TNUoS charging calculations. Affected parties need to assess their compliance position and, if they intend to claim cost recovery, engage with the ESO on the mechanics.

Compliance timeline. The 72-hour resilience requirement is now live as a Grid Code obligation. Parties that do not yet comply need to retrofit or make alternative arrangements. There is no extended transition period specified in the source documents — GC0156 is approved and in force.

Related decisions. This sits within a wider suite of code modifications related to the Electricity System Restoration Standard. Ofgem's decision page links to these related modifications. The Restoration Standard itself replaced the previous Black Start arrangements, shifting from a purely contracted model (where the ESO procured Black Start services from willing providers) to a universal resilience obligation on all connected parties. CMP398 addresses the cost consequence of that shift.

The broader pattern. This is a textbook example of a system security obligation being socialised through use-of-system charges. The obligation is imposed through the Grid Code, the cost recovery mechanism is created through the CUSC, and the bill lands on TNUoS payers. The question — as with all socialised costs — is whether the resilience benefit justifies the additional charge, and whether a universal obligation is more efficient than the previous approach of contracting for Restoration Services from a smaller pool of willing and capable providers.