Ofgem opened the first application window for the Long Duration Electricity Storage (LDES) cap and floor scheme on 8 April 2025. After notifying Ofgem of an intent to apply (such notice being served no later than 22 April 2025), the next stage of the process is an initial submission by developers to demonstrate that their projects meet the eligibility criteria for the scheme. The closing date for those initial submissions is 9 June 2025.

Ofgem has issued its "Guidance for the cap and floor scheme application: Long Duration Electricity Storage" dated 8 April 2025, Appendix 2 of which defines the eligibility criteria for qualifying LDES projects (the Eligibility Criteria Assessment Framework). Projects must meet all six of the following criteria to be considered eligible for the scheme:

1. Deliverability

Projects must demonstrate a credible plan for completion by either 2030 (Track 1) or 2033 (Track 2). This includes providing:

• Business/project plan: Including project description, location, specification, implementation plan, team structure, schedule and milestones.
• Project schedule: Showing development and construction activities, potential impacts and mitigation plans, critical path with interdependencies and a Commercial Operations Date that meets eligibility requirements.
• Engineering and design study: Evidence of upfront engineering design/optioneering (FEED) appropriate to the project's level of maturity (together with details of the contracts under which such activities were procured).
• Cost estimates: Deterministic cost estimates equivalent to AACE Class IV standard or above.
• Procurement and supply chain: Identification of key suppliers, signed contracts, assessment of suppliers' availability and capacity.
• Financing plans: Evidence describing the financing/capital structure of the project and its principal sponsor(s).
• Licensing and permitting: Evidence of land rights and environmental permitting.

2. Grid connection

Projects must provide evidence that a grid connection application has been submitted and/or a firm grid connection offer has been received.

Projects must also demonstrate consideration of key risks to the delivery of the grid connection by the proposed project completion date.

3. Planning consent

The requirements differ based on the project track:

• Track 1 projects (deliverable by 2030): Evidence demonstrating the ability to secure planning consent in the required delivery timescales, including evidence of initial engagement and land rights.
• Track 2 projects (deliverable by 2033): Evidence demonstrating that planning consent will be in place (obtained) by the end of Q3 2025.

4. Minimum capacity

Projects must provide evidence that the scheme can maintain a minimum discharge capacity of:

• at least 100MW for stream 1 projects; or
• at least 50MW for stream 2 projects.

5. Duration

Projects must demonstrate that the scheme will be able to discharge power continuously at full discharge capacity for a minimum duration of eight hours.

Technical documentation and operational plans must confirm that this minimum duration can be met and performance maintained throughout the regime period.

6. Technological readiness

Projects must demonstrate that they meet Technological Readiness Level (TRL) 8 or 9.

• For TRL 9 projects: Sufficient evidence demonstrating the project's TRL, though detailed evidence is not required for technologies known to be at TRL 9.
• For TRL 8 projects: Sufficient detailed evidence demonstrating the project's TRL.

Additional requirements for refurbishments and expansions

For significant refurbishments and expansions, projects must explain why the new capacity requires cap and floor regime support and cannot obtain adequate funding solely through merchant project financing or existing schemes such as the capacity market.

Only the cost of the new capacity from the significant refurbishment or expansion can be supported by the cap and floor scheme.

Assessment approach

Each criterion will be evaluated using a binary pass/fail approach based on the information, documentary evidence and reasoning provided by applicants.

To pass the eligibility stage, a project must meet the requirements of every eligibility criterion. Only projects that pass all eligibility criteria will proceed to the Cost Benefit Analysis (CBA) project assessment stage.

Ofgem will conduct the eligibility assessment (to confirm whether the application meets the eligibility criteria) with a view to issuing decisions in Q3 2025.