Post: Ofgem approves P511

Ofgem approves P511

Ofgem has approved BSC Modification P511, introducing revised eligibility criteria for consumer-led flexibility and generation assets participating in the wholesale electricity market through the Virtual Trading Party (VTP) arrangements established by P415.

Background to the changes

In October 2023, Ofgem approved BSC code modification P415: Facilitating access to Wholesale Markets for flexibility dispatched by Virtual Lead Parties (VLPs). P415 aimed to facilitate access to wholesale electricity markets for flexibility dispatched by independent aggregators, introduced mutualised compensation for suppliers who have been affected by this activity and introduced the role of a VTP as a BSC party. VTPs are independent aggregators who trade a customer’s flexibility in the wholesale market.

P511 was raised following concerns about the rapid increase in the volume and cost of the P415 mutualised compensation fund. Ofgem’s noted that approximately £19M of Supplier compensation cashflow had been mutualised between 1 September 2025 and 28 February 2026. A key concern was that some generation assets could potentially receive payments through both their VTP and their existing power off-taker arrangements. At the same time, actions taken by VTPs can trigger mutualised compensation payments to Suppliers. This created a risk that arrangements intended to support flexibility could instead lead to increased costs for consumers. There were also concerns that this activity was moving away from the intent of P415: providing a route-to-market for that do not have other viable routes to the wholesale market.

What’s changing?

P511: Eligibility Boundaries for Generation Participation in P415, which was approved on 10 August, introduces eligibility criteria intended to distinguish between consumer-led flexibility and predominantly export-led generation assets. Eligibility will be determined using metered data, based on the largest half-hourly Active Export recorded for a Metering System Identifier (MSID) Pair over the previous 365 days:

• below 2MW: MSID Pairs remain eligible to participate through the P415 VTP route.

• above 10MW: MSID Pairs are ineligible to participate through this route.
• between 2MW and 10MW: an additional assessment applies, comparing Active Export with Final Import over the previous 30 days. An MSID Pair will be ineligible where it is net exporting on this adjusted basis.

The approach is intended to retain a route-to-market for smaller export-capable sites, particularly where P415 may be their only practical route-to-market, while limiting access for predominantly export-led sites that are more likely to have alternative routes available and should generally be able to access the market through other routes.

P511 will come into effect on 24 August 2026. P509 and P510 are still at working group stage, and further changes could be implemented. But the new eligibility thresholds introduced under P511 mean that the smaller assets that P415 was designed for retain access and that the VTP route genuinely adds flexibility to the system. But assets that sit in the 2MW-10MW band will need careful monitoring of their export profile to maintain or lose eligibility.

The central question should remain how best to support a growing flexibility market that delivers genuine value to consumers. Ensuring that incentives remain aligned with system needs, and that costs are justified by measurable benefits, will be key to maintaining confidence in the framework as the energy system continues to evolve.

Glossary

• P509 (Consumer benefits and safety net for Demand Side Response participation in the wholesale market) proposes a framework to assess whether individual participants are delivering outcomes consistent with the original impact assessment, and to take action where they are not. The challenge lies in the complexity of applying a baseline at the level of individual participants. Such an approach risks being difficult to administer and open to dispute.
• P510 (Introducing Direct Compensation for Virtual Trading Party actions in the Wholesale Market) represents a more fundamental redesign. It introduces a direct compensation mechanism, requiring the flexibility provider to pay the host supplier for the impact of demand changes, thereby removing the need for mutualisation. It also expands the scope of P415 to include both increases and reductions in demand.
• P511 (Removing Large-Scale Generation Assets from P415 Wholesale Market Activation Notifications) takes a direct approach by excluding generators above a defined threshold from participating in P415. This targets the perceived source of unintended behaviour without fundamentally altering the design of the mechanism. As a result, it is widely seen as a pragmatic and low-risk intervention that could be implemented on an urgent basis.