Mast Energy Developments PLC

(Incorporated in England and Wales)

(Registration Number: 12886458)

LEI :213800HFVHGJ9YGO9F71

Share code on the LSE: MAST

ISIN: GB00BNG90H86

('MED' or 'the Company')

Dated: 23 September 2025

Mast Energy Developments PLC

("MED" or the "Company")

MAST's Pyebridge 8.1 MW FlexGen Power Asset Boosts Income

With 15-Year Maximum Capacity Market Contract

London, UK - Mast Energy Developments PLC (LSE: MAST) is pleased to announce, further to its RNS announcement dated 31 July 2025, that the Company's 100% owned Pyebridge 8.1 MW operational flexible generation power asset has significantly boosted its income with a guaranteed 15-year Capacity Market contract, the highlights and details of which are outlined below.

Key Highlights:

·    The UK Capacity Market ("CM") is a government-backed scheme designed to ensure security of electricity supply by providing guaranteed income payments to reliable sources of capacity, such as MAST's flexible generation power assets;

·    The benefits of a CM contract include guaranteed, stable, long-term revenues, reducing exposure to wholesale market volatility;

·    Pyebridge successfully fulfilled the necessary requirements under the CM rules and submitted an application for the upcoming CM auction, for a maximum tenure 15-year T-4 CM contract at the asset's maximum possible generation capacity of c. 8.1 MW;

·    Pyebridge already has an uninterrupted series of existing 1-year CM contracts covering the period until 2029 and amounting to cumulative total guaranteed gross profit income of c. £1.7 million, as previously announced;

·    This latest CM application and associated CM contract will cover the period from 2029 until 2044, and provide Pyebridge and MED with a significant boost in uninterrupted guaranteed gross profit income until 2044;

·    Assuming that the upcoming T-4 CM auction price clears at the same price as last year of £60,000 per MW/annum, which is expected, means that Pyebridge's new CM contract will have a cumulative total guaranteed gross profit income value of c. £6.5 million (before annual inflation increases), in addition to the c. £1.7 million of its existing CM contracts., totaling c. £8.2 million; and

·    The CM contract income is over and above the site's wholesale market revenue via its PPA with Statkraft, and Embedded Benefits revenue, currently yielding c. £276,000 per MW per annum, as previously announced.

Pieter Krügel, Chief Executive Officer of MAST Energy, said: "We are delighted with the Pyebridge application for a maximum tenure 15-year T-4 CM contract at the maximum possible generation capacity of c. 8.1 MW. This application was made possible by the comprehensive refurbishment programme which we successfully implemented at Pyebridge last year, within expected timeline and budget. The new CM contract will further boost Pyebridge's economics and provide attractive guaranteed cashflows up to 2044."

About MAST Energy Developments PLC:

MAST Energy Developments PLC (LSE: MAST) is a UK-based developer, operator and owner of flexible generation power assets. The Company has deep expertise in infrastructure planning, grid access, gas access, and efficient power supply. Its new AI power supply strategy is intended to position MAST as a leading AI infrastructure platform on the London Stock Exchange (read more here).

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Forward-Looking Statements:

This RNS announcement contains forward-looking statements. These statements involve risks and uncertainties that could cause actual results to differ materially from those expressed or implied. No statement in this announcement is intended as a profit forecast, and forward-looking statements speak only as of the date of this announcement. The Company undertakes no obligation to update such statements except as required by law and regulations.

ENDS

This announcement contains inside information for the purposes of the UK version of the Market Abuse Regulation (EU No. 596/2014) as it forms part of United Kingdom domestic law by virtue of the European Union (Withdrawal) Act 2018 ('UK MAR'). Upon the publication of this announcement, this inside information is now considered to be in the public domain.

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