IN Brief:
- DESNZ is consulting on stronger Capacity Market delivery assurance, including enhanced testing and more stringent data requirements.
- Consumer-led flexibility proposals include revisions to demand-side response de-rating and controls around secondary trading behaviour.
- Any agreed changes are intended for Prequalification 2027 ahead of Capacity Market auctions taking place in 2028.
The Department for Energy Security and Net Zero is proposing another round of Capacity Market rule changes, with tighter delivery assurance, stronger data requirements, and revised treatment of consumer-led flexibility intended to take effect before the 2028 auction cycle.
The consultation is aimed at Prequalification 2027, subject to the final government response and parliamentary time. It builds on earlier changes to a mechanism that now has to accommodate conventional generation, storage, interconnection, and increasingly sophisticated forms of flexible demand.
Delivery assurance sits at the centre of the proposals. Capacity Market agreements provide revenue in return for dependable capacity being available when the electricity system is under stress, making the credibility of contracted megawatts at least as important as the volume procured at auction.
DESNZ is considering enhanced testing and more stringent data requirements to increase confidence that successful Capacity Market Units can perform. The detail varies across resource types, but the direction is towards more evidence of physical and operational capability rather than relying primarily on declarations at the point of entry.
That becomes increasingly important as the Capacity Market technology mix broadens. A gas turbine, battery, interconnector, and aggregated portfolio of flexible customers can all contribute to security of supply, but their constraints are fundamentally different.
A conventional generator may face fuel, start-time, maintenance, and minimum-running constraints. A battery is limited by state of charge and discharge duration. An interconnector depends on neighbouring-system conditions and available transfer capacity. Consumer-led flexibility depends on whether customers can alter demand when required and for long enough to satisfy the obligation.
The consultation therefore proposes further changes to the treatment of consumer-led flexibility, which remains described as Demand Side Response in Capacity Market legislation. DESNZ wants a more accurate DSR de-rating methodology and is also examining secondary trading behaviour.
De-rating translates nominal capacity into the amount of dependable capacity recognised for security-of-supply purposes. A 10MW resource does not necessarily contribute 10MW of dependable capacity if historical or technical evidence indicates that it will sometimes be unavailable or unable to sustain its response.
The resulting factor has direct financial consequences. A higher de-rating factor allows more of an asset’s nominal capability to enter the auction and potentially earn Capacity Market revenue, while a lower factor reduces the amount credited to the same physical installation.
For aggregated demand-side resources, arriving at that factor is difficult because apparently similar portfolios can behave very differently. Industrial processes, commercial buildings, behind-the-meter batteries, standby generation, and flexible computing loads may all reduce net demand, but their duration, availability, and ability to repeat the response are not identical.
Secondary trading creates another assurance problem. It allows capacity providers to transfer obligations where circumstances change, helping participants manage delivery risk without necessarily abandoning an agreement altogether.
The flexibility is useful only if the replacement obligation retains the security value originally purchased. Trading contractual responsibility to a resource with materially weaker availability would preserve the paperwork while degrading the insurance the Capacity Market is supposed to provide.
DESNZ is also proposing mitigations where required data flows cannot be established promptly for reasons outside a capacity provider’s control. That is intended to avoid termination where an asset may be technically capable of delivery but a supporting data process has failed elsewhere.
The distinction has to be drawn carefully. Capacity arrangements increasingly depend on metering, registration, communications, and central data systems to verify participation and performance. If missing data is always excused, assurance weakens; if every central-system failure creates a termination event, participants inherit risks they cannot manage.
The remaining proposals include administrative and operational amendments intended to improve transparency, consistency, and enforceability of the Capacity Market Rules. Such changes are less visible than auction prices but can materially affect developers financing assets against multi-year capacity revenues.
The wider policy objective is to retain enough dependable capacity as the system becomes more renewables-led. That does not necessarily mean procuring more conventional generation: storage, flexible demand, and interconnection can all provide useful capacity where their limitations are understood and represented accurately.
Testing, data, and de-rating are therefore different parts of the same assurance problem. Testing demonstrates capability, data provides evidence of performance, and de-rating converts the expected dependability of that resource into the quantity recognised in the auction.
The balance is awkward. Requirements that are too loose allow speculative or weak capacity to collect agreements; requirements that are unnecessarily burdensome raise entry costs and can exclude newer technologies capable of providing useful flexibility.
If adopted, the 2027 prequalification process will provide the first practical test of the new package. Participants will be concerned with evidence, testing, and credited capacity. The electricity system has a simpler requirement: when a tight period arrives, the megawatts bought through the Capacity Market need to exist outside the spreadsheet.
