Long Duration Electricity Storage (LDES) window 1 eligibility assessment outcome

Details of outcome  

Ofgem has completed the eligibility assessment for Window 1 of the Long Duration Electricity Storage (LDES) Cap and Floor scheme, following the opening of the first application window on 8 April 2025 and the publication of the Eligibility Criteria Assessment Framework (ECAF).

Projects that met the eligibility criteria have been confirmed as eligible and will now proceed to the Project Assessment stage, which opens on 23 September 2025. This outcome marks a key milestone in the delivery of the LDES Cap and Floor scheme and reflects the range of technologies and proposals emerging to support the UK's transition to net zero.

Eligible projects will now proceed to the project assessment stage, which started on 23 September 2025. Read the Long Duration Electricity Storage (LDES) project assessment multi-criteria approach (MCA) framework for more information. 

Read the full outcome

Long Duration Electricity Storage: cap and floor application window 1

Today, 8 April 2025, we open the first application window for Long Duration Electricity Storage (LDES) projects under the cap and floor regulatory scheme. This follows the March 2025 Technical Decision Document published with the government. We aim to approve the first projects by Q2 2026.

The cap and floor regime provides a minimum revenue floor for LDES operators to manage high capital costs and long build times, while the revenue cap lowers costs for consumers. The government introduced the scheme to encourage LDES investment and appointed Ofgem as the regulator based on our interconnector cap and floor experience.

We invite applications from developers who can deliver projects by 2030 and 2033 to meet the government's Clean Power 2030 target. LDES project developers must submit their applications by 9 June 2025 to be considered in this round. Further details are available in the decision letter and the application guidance below.  

Interested parties should notify us via email at LDES@ofgem.gov.uk using the subject heading 'LDES SCHEME APPLICATION: [Project Name]' by 22 April 2025 of their intent to submit projects within this first application window and specify which track they wish to be considered under, project location and technology type. This helps us to plan ahead. Please send any general feedback to the same email.